osync/osync v1.2.lyx

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\pdf_title "Osync Configuration guide"
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\begin_body

\begin_layout Title
osync v1.2 Documentation
\end_layout

\begin_layout Author
(C) 2013-2017 by Orsiris de Jong
\end_layout

\begin_layout Date
25 March 2017
\end_layout

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\begin_inset CommandInset href
LatexCommand href
name "http://www.netpower.fr/osync"
target "http://www.netpower.fr/osync"

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offset "0.5ex"
width "100col%"
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\begin_layout Section
Introduction
\end_layout

\begin_layout Subsection
Quickstart guide
\end_layout

\begin_layout Standard
osync is a command line two way synchronization tool for Linux / BSD / Android
 / Busybox / MacOSX and Windows, with an emphasis on reliability and automation
 on low bandwidth links.
\end_layout

\begin_layout Standard
For those who think TL;DR, a quickstart guide can be found in the README.md
 file.
\end_layout

\begin_layout Subsection
Basic synchronization problems
\end_layout

\begin_layout Standard
Synchronization is usually found in two flavors, bloc level sync and file
 level sync.
 While whole bloc level synchronization is generally a good way of doing,
 it's also very greedy in network ressources and is not easy to setup.
 That's where file level sync comes in handy, where only some directories
 & files need to be synced.
\end_layout

\begin_layout Standard
Imagine you're syncing two remote offices of a same company.
 If you're syncing a user's home directory or it's roaming profile as a
 night task, the next day, the user will find it's roaming profile up to
 date at the remote office.
\end_layout

\begin_layout Standard
But what would happen if two users work on the same file in a public folder,
 at the same time, on both offices ? Some sync software would stop sync
 and ask what to do.
 Others might simply deleted the oldest version of the file, even if it
 was modified on both sides.
\end_layout

\begin_layout Standard
Also, what would happen if a user uploads a lot of data ? If the link between
 both offices cannot handle enough data transfer in a given time, any other
 sync task won't be run, and the sync would continue during the day, when
 bandwidth is necessary elsewhere.
\end_layout

\begin_layout Standard
What would happen if a power fault occurs while synchronization is going
 on ?
\end_layout

\begin_layout Subsection
What osync can do
\end_layout

\begin_layout Subsubsection
Making synchronization reliable
\end_layout

\begin_layout Standard
osync is designed to synchronize two folders on both local and / or remote
 systems.
\end_layout

\begin_layout Standard
It is time controlled, which means you can decide how much time it should
 spend on a sync task before stopping it and launching the next one.
\end_layout

\begin_layout Standard
It's designed to resume failed or stopped sync tasks in order to gain as
 much time as possible, or totally restart the sync task if resuming fails.
\end_layout

\begin_layout Standard
It can keep multiple versions of a file in case of conflicts.
\end_layout

\begin_layout Standard
It handles soft deletion.
 If a user deletes a file on replica A, it will move that file on replica
 B to the 
\begin_inset Quotes sld
\end_inset

.osync_workdir/deleted
\begin_inset Quotes srd
\end_inset

 folder.
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\begin_layout Standard
It will automatically clean old files (soft deleted and conflict backups)
 after a defined amount of days.
\end_layout

\begin_layout Standard
It will perform various checks before launching a synchronization, like
 checking for free disk space against a defined minimum value.
\end_layout

\begin_layout Subsubsection
Making a sysadmin's life easier
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osync is also desgined to ease synchronization setups.
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\begin_layout Standard
It will trigger an email alert including the whole sync process execution
 log if a warning / error is found.
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\begin_layout Standard
Pre-processing and post-processing commands can be launched on local and
 / or remote systems, which may be useful to launch snapshot software, flush
 or standby virtual machines, etc).
\end_layout

\begin_layout Standard
Multiple concurrent instances of osync can be run as long as they don't
 sync the same replicas at the same time.
\end_layout

\begin_layout Standard
A batch processing script is included (osync-batch.sh) to launch sequential
 sync tasks.
 Failed sync tasks are rerun if every other task has completed and there's
 still some time left in a given timespan.
\end_layout

\begin_layout Standard
osync can use rsync or ssh tunnel compression to gain bandwidth.
 Bandwidth can also be limited for slow link sharing.
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\begin_layout Standard
It can be run in quicksync mode for the impatient (nothing to configure
 except the replica paths), or with a full blown config file.
\end_layout

\begin_layout Standard
You may run osync manually, schedule it with cron, or have it monitor a
 directory as a daemon and launch sync tasks on file modifications.
\end_layout

\begin_layout Standard
osync has been deeply tested on RHEL / CentOS 5, 6 & 7, Fedora 23, 24 &
 25, Debian 6, 7, & 8, Linux Mint 14, 17 & 18, FreeBSD 8.3, 10.3 & 11, pfSense
 2.x, Mac OS X, Android using termux, Windows 10 bash, and msys / msys2 &
 cygwin environments.
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\begin_layout Subsubsection
What osync cannot do
\end_layout

\begin_layout Standard
Contrary to most sync tools, osync is stateful, which means that it doesn't
 need an agent installed on computers it synchronizes to.
 This makes it gain some degree of fault tolerance with WAN links.
\end_layout

\begin_layout Standard
But this also has some drawbacks, there is a cornercase when a user deletes
 a file while the synchronisation is happening, the file won't get deleted
 on the other side because the sync is actually updating the directory states
 at the same time they get changed.
 Even if this happens only on very big deployments in some rare occasions
 because of the time osync takes to sync, there is still a chance that your
 deletion wouldn't make it.
 Generally speaking, the easiest way is to setup osync as a crontask and
 launch it by night in order to avoid any possible 
\end_layout

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The good point is, osync is built from ground up to keep your data safe,
 and there's no chance it will delete anything you didn't want.
\end_layout

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osync is a simple bash script that relies on other tools like rsync.
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Hence, it has some advantages and disavantages:
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\begin_layout Standard
Advantages:
\end_layout

\begin_layout Standard
- Easily customisable
\end_layout

\begin_layout Standard
- Fast
\end_layout

\begin_layout Standard
- Agentless
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\begin_layout Standard
Disavantages:
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\begin_layout Standard
- There's no way to detect file moves.
 If you move a directory on replica A, osync will soft delete the directory
 on replica B and copy the new directory from replica A.
\end_layout

\begin_layout Standard
- There's no multi-master replication in osync V1.
 Hence, if you want to sync replicas A, B, and C using osync, you'll have
 to use one of the following schemas:
\end_layout

\begin_layout Paragraph
Replicate 3-way with A as master
\end_layout

\begin_layout Standard
Run the following tasks sequentially where A is the initiatior:
\end_layout

\begin_layout Standard
Replicate A & B
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\begin_layout Standard
Replicate A & C
\end_layout

\begin_layout Standard
Replicate A & B
\end_layout

\begin_layout Paragraph
Replicate 3-way with A & B as masters
\end_layout

\begin_layout Standard
Run the following tasks from each system.
 Be sure they won't run concurrently (osync will detect that another replication
 is still running, and abort the current one):
\end_layout

\begin_layout Standard
Replicate A & B where A is the initiator
\end_layout

\begin_layout Standard
Replicate B & C where B is the initiator
\end_layout

\begin_layout Standard
Replicate C & A where C is the initiator
\end_layout

\begin_layout Subsection
Why use osync
\end_layout

\begin_layout Standard
There are a lot of file sync tools out there, some probably better than
 osync depending on the use case.
\end_layout

\begin_layout Standard
osync has been basically written to be low bandwidth friendly, with resume
 options for unstable internet links (but it will also do great on a fiber
 link :)).
\end_layout

\begin_layout Standard
It has also been written to be a setup and forget tool, without any user
 interaction like manual conflict resolution.
\end_layout

\begin_layout Standard
osync also is one of the few tools that
\series bold
 support ACL synchronization
\series default
.
\end_layout

\begin_layout Standard
At last, osync consumes very little RAM and CPU ressources and is suitable
 from lower en hardware up to serveres.
\end_layout

\begin_layout Subsection
How osync tries to resolve sync issues
\end_layout

\begin_layout Standard
Let's get back to the example above, where osync is used to sync two remote
 offices with users' home directories.
\end_layout

\begin_layout Standard
Now imagine a user uploaded 100GB of data, and the WAN link between local
 and remote systems can only handle 6GB/hour of data transfer.
\end_layout

\begin_layout Standard
Now if osync is scheduled every night at 10:00 pm, and it's configured to
 run for maximum 10 hours, it would stop at 6am, after having transferred
 60GB.
\end_layout

\begin_layout Standard
Then, on the next day, it would transfer the remaining 40GB from 10:00 pm
 to about 3:30am.
\end_layout

\begin_layout Standard
Also, if you run sequential instances of osync (with osync-batch), one per
 user directory for example, you can decide how much time osync should spend
 per user.
 So if a user uploads too much data, and osync cannot finish the synchronization
 task for that user directory in a given timespan, it will stop that sync
 task and run next user synchronization task so every user sync task gets
 run, regardless of the amount of data.
 If there's time left, osync-batch reprograms the user sync task that has
 been stopped.
\end_layout

\begin_layout Subsection
Naming in this document
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\begin_layout Standard
osync's goal is to synchronize two directories, that can be hosted on the
 same computer or two different ones.
\end_layout

\begin_layout Standard
The computer that runs osync must have at least one of these two directories
 mounted, and will be called the 
\emph on
local system.
\end_layout

\begin_layout Standard
The first directory to sync on the local system is called the 
\emph on
initiator replica
\emph default
.
\end_layout

\begin_layout Standard
The other directory, called the 
\emph on
target replica
\emph default
 can be hosted on the 
\emph on
local system
\emph default
, or on another computer which will be called the 
\emph on
remote system
\emph default
.
 In that case, the 
\emph on
local system
\emph default
 will connect to the 
\emph on
remote system
\emph default
 through an ssh tunnel and synchronize both 
\emph on
initiator
\emph default
 and 
\emph on
target replicas
\emph default
.
\end_layout

\begin_layout Standard
Any osync configuration file that gets executed is called an 
\emph on
osync task
\emph default
.
\end_layout

\begin_layout Standard
In the following examples, a special user called 
\emph on
syncuser
\emph default
 is used for osync.
\end_layout

\begin_layout Subsection
How osync solves sync conflicts
\end_layout

\begin_layout Standard
Conflict resolution is done automatically.
 When a file is modified on both replicas, osync compares the timestamps
 on both replicas and keeps the most recent file.
\end_layout

\begin_layout Standard
In the highly uncommon case where both files have the exact same timestamp,
 a configuration value called CONFLICT_PREVALANCE choses the which replica's
 file will be kept.
 By default, Initiator is chosen, unless specified otherwise in the config
 file.
\end_layout

\begin_layout Standard
The file that isn't kept is copied to 
\begin_inset Quotes sld
\end_inset

.osync_wordir/backups
\begin_inset Quotes srd
\end_inset

 directory of the replica by default, with its full path relative to the
 replica, unless specified otherwise by the CONFLICT_BACKUP configuration
 value.
\end_layout

\begin_layout Standard
After an amount of days set by CONFLICT_BACKUP_DAYS, which is 30 by default,
 the backed up file is deleted.
\end_layout

\begin_layout Standard
If CONFLICT_BACKUP_MULTIPLE is set to YES (disabled by default), multiple
 versions of the backed up files are kept, with a timestamp suffix like
 
\begin_inset Quotes sld
\end_inset

2016.12.31-12.00.01
\begin_inset Quotes srd
\end_inset

.
\end_layout

\begin_layout Section
Prerequisites
\end_layout

\begin_layout Subsection
General packages
\end_layout

\begin_layout Standard
osync is a bash script that will work with 
\series bold
bash version 3.2 or better
\series default
, but will not run with ksh / tsh / csh or other shells.
 Usually bash comes with most linux distributions.
\end_layout

\begin_layout Standard
Here's a list of commands to install basic prerequisites on both local and
 remote machines.
 
\end_layout

\begin_layout Standard
Note that openssh-clients are only needed on local machine if connecting
 remotely and sshpass is only needed if dealing with password files instead
 of RSA keys.
\end_layout

\begin_layout Standard
The sudo package is only needed if you plan to run osync remotely with a
 standard user that gets sudo privileges.
\end_layout

\begin_layout Standard
Also, inotify-tools / fswatch  is only needed if you plan to run osync in
 daemon mode (wherever inotify-tools is available).
\end_layout

\begin_layout Itemize
RHEL / CentOS
\end_layout

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yum install rsync coreutils openssh-clients sshpass inotify-tools
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Debian / Ubuntu / Mint
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apt-get install rsync openssh-client sshpass inotify-tools
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FreeBSD
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pkg install bash rsync sshpass inotify-tools sudo
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MacOS X
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brew install rsync fswatch	
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MSYS (use management interface to install tools)
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msys-base msys-coreutils-ext msys-rsync procps openssh-client
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MSYS2
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pacman -S rsync procps openssh-client
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Cygwin (use management interface to install tools)
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rsync procps-ng openssh wget
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termux (Android / Busybox)
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apk --no-cache add bash rsync openssh-client
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\begin_layout Standard
Additionnaly, on termux, shebangs need to be modified to work with the system
 root.
 Example on how to get osync.sh working:
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termux-fix-shebang osync.sh
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\begin_layout Subsubsection
Mail alert prerequisites
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\begin_layout Standard
osync can send alert emails on warnings / errors.
\end_layout

\begin_layout Itemize
On standard linux distros, BSD, MacOSX and Windows 10 bash, osync relies
 on your system-wide configured mail sending support in order to send alerts.
 It will try to use mail / mutt & sendmail.
 Please make sure that your system is configured to allow outgoing mail.
 You may check for osync mail in your mail logs (example: /var/log/maillog
 on RHEL / CentOS).
\end_layout

\begin_layout Itemize
On android / busybox, you will need sendmail and openssl-tools if you plan
 to use mail encryption (TLS/SSL)
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apt --no-cache add sendmail openssl-tools
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\end_inset


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On Cygwin / MSYS2, mail support is done via mailsend (https://github.com/muquit/m
ailsend) or sendmail (http://caspian.dotconf.net/menu/Software/SendEmail/)
 which have to be executable path (%PATH% variable, or just place them in
 system32).
\end_layout

\begin_layout Subsubsection
Daemon mode prerequisites
\end_layout

\begin_layout Standard
osync can run in daermon mode in order to detect file modifications.
 This mode works on Linux / BSD and MacOSX.
\end_layout

\begin_layout Standard
On Linux and BSD, please install the following package:
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inotify-tools
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\end_inset


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\begin_layout Standard
On FreeBSD, you might want to increase kern.maxfiles tunable if you plan
 to use inotify-tools for applications that need to monitor activity of
 a lot of files.
 Modify /boot/loader.conf and add 
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status open

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kern.maxfiles="25000"
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\end_inset


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On MacOS X, you will need to install fswatch with brew:
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brew install fswatch
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\end_inset


\end_layout

\begin_layout Subsection
Downloading osync
\end_layout

\begin_layout Standard
osync can be downloaded on the author's site (stable version) or on github
 (stable or latest dev snapshot).
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Getting osync via author's site
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$ wget http://netpower.fr/projects/osync/osync.v1.2.tar.gz
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$ tar xvf osync.v1.2.tar.gz
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\begin_layout Standard
Getting osync via github (remove the -b 
\begin_inset Quotes sld
\end_inset

stable
\begin_inset Quotes srd
\end_inset

 if you want latest dev snapshot)
\end_layout

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$ git clone -b "stable" https://github.com/deajan/osync
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On Linux / BSD / Windows 10 bash, Once you downloaded osync, enter into
 the newly created folder and run the install script
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$ bash ./install.sh
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This will copy osync to /usr/local/bin and create /etc/osync with a test
 sync.conf file.
\end_layout

\begin_layout Standard
It will also copy daemon required files to /etc/init.d or /usr/lib/systemd/system
 and /etc/systemd/user depending on your distribution.
\end_layout

\begin_layout Standard
On MacOS X, msys, Cygwin and termux (Android), you may directly use osync.sh
 script.
\end_layout

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Uninsalling is done by using
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$ bash ./install.sh --remove
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There is also an RPM package available for Fedora & CentOS, which will install
 all binaries to /usr/bin instead of /usr/local/bin in order to enforce
 good practices.
\end_layout

\begin_layout Subparagraph
Please note that when using the RPM packages, the binaries paths in this
 document shall be read as /usr/bin instead of /usr/local/bin.
\end_layout

\begin_layout Subsection
File synchronization
\end_layout

\begin_layout Standard
File sync tasks don't need any special configurations.
 You only have to worry about your sync user having the filesystem permissions
 to read / write on both replicas.
\end_layout

\begin_layout Standard
A good way is to make your user member of the files' group that has full
 permissions.
\end_layout

\begin_layout Standard
Another way to achieve this is using ACLs if your filesystem supports them.
 You can add the following permissions for user "syncuser" on directory
 "/home/web".
 Setting a default rule will add rights on new files.
\end_layout

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# setfacl -dRm u:syncuser::r-x /home/web
\end_layout

\end_inset


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\begin_layout Standard
Be aware that ACLs are tricky and default unix permissions serve as mask
 for ACLs.
\end_layout

\begin_layout Standard
Make always sure you can read /write to both replicas with your sync user:
\end_layout

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# su syncuser
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$ cat /initiator/replica/test.file
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$ touch /initiator/replica/othertest.file
\end_layout

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\end_layout

\begin_layout Standard
Repeat that step for the target replica.
\end_layout

\begin_layout Subsection
Time setup
\end_layout

\begin_layout Standard
WARNING: osync's conflict resolution relies on timestamps, so it is very
 important for all systems osync runs / syncs to, to have a reliable and
 common timesource.
\end_layout

\begin_layout Standard
Please consider setting up NTPD first before you plan to run osync.
\end_layout

\begin_layout Subsection
\begin_inset CommandInset label
LatexCommand label
name "subsec:Performing-superuser-backups"

\end_inset

Performing superuser sync
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\begin_layout Standard
osync can be run as superuser on the remote side, which should always be
 avoided by granting the read / write permissions to a dedicated sync user
 to both replicas.
\end_layout

\begin_layout Standard
There are still some cases where osync needs to be run as superuser, especially
 when syncing system files.
\end_layout

\begin_layout Standard
In those cases, osync can be run as dedicated sync user and ask for sudo
 permissions (if system permits it) for specific commands, or directly run
 as root (which isn't recommended).
\end_layout

\begin_layout Standard
In order to be able to use the sudo command without having to enter a password,
 you’ll need to modify remote system to allow the following commands to
 be run as superuser.
\end_layout

\begin_layout Standard
Use visudo to edit the sudoers file (or carefully edit /etc/sudoers yourself)
 and add the following
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

syncuser ALL= NOPASSWD:SETENV:/usr/bin/rsync,/usr/bin/bash
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Please note that the SETENV parameter is required so osync can send it's
 local variables as remote environment variables (equals sudo -E).
\end_layout

\begin_layout Standard
You might check the right paths to your commands, especially on some FreeBSD
 environments where rsync might be in /usr/local/bin instead of /usr/bin
 (example to get path for rsync executable): 
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ type rsync
\end_layout

\end_inset


\end_layout

\begin_layout Standard
You'll also need to disable requiretty in /etc/sudoers by adding the following
 line:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

Defaults:syncuser   !requiretty
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Once your standard sync user is granted to run what osync needs, you can
 enable sudo in osync's config file:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SUDO_EXEC=yes
\end_layout

\end_inset


\end_layout

\begin_layout Standard
You should be aware that there is a risk with having rsync command run as
 superuser.
 A user who can run rsync command as superuser can upload any file he wants
 to the system, including a tweaked /etc/sudoers or /etc/passwd file.
 Please read chapter 
\begin_inset CommandInset ref
LatexCommand ref
reference "subsec:Enhancing-remote-backup"

\end_inset

 to secure your installation.
\end_layout

\begin_layout Subsection
Remote sync
\end_layout

\begin_layout Standard
osync can perform local or remote synchronization tasks.
 For local sync, pelease refer to chapters 
\begin_inset CommandInset ref
LatexCommand ref
reference "sec:Running-Osync-in"

\end_inset

, 
\begin_inset CommandInset ref
LatexCommand ref
reference "sec:Running-Osync-with-config-file"

\end_inset

and 
\begin_inset CommandInset ref
LatexCommand ref
reference "sec:Running-Osync-as-daemon"

\end_inset

.
\end_layout

\begin_layout Standard
Remote synchronization is done through an SSH tunnel.
 To be able to establish such a tunnel without having to enter a password,
 you’ll have to generate a pair of private and public RSA keys.
\end_layout

\begin_layout Standard
The private part is kept by the computer that initiates the connection,
 the local system.
 The public part is kept on the remote system.
\end_layout

\begin_layout Standard
The following steps will be required to generate a ssh key:
\end_layout

\begin_layout Standard
Create a dedicated sync user and log in as that user on the local system
 to perform the following actions.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ssh-keygen -t rsa
\end_layout

\end_inset


\end_layout

\begin_layout Standard
This should create two files named ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub
\end_layout

\begin_layout Standard
You should also create a dedicated sync user on the remote system.
\end_layout

\begin_layout Standard
Copy the public part of the RSA pair to the remote system with scp (replace
 22 with your ssh port number if needed).
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ scp -p 22 ~/.ssh/id_rsa syncuser@remotesystem.tld:/home/syncuser/.ssh/authorized_
keys
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Make sure the file is only readable and owned by the syncuser on the remote
 system.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ chmod 600 /home/syncuser/.ssh/authorized_keys
\end_layout

\begin_layout Plain Layout

$ chown syncuser:root /home/syncuser/.ssh/authorized_keys
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Now you should be able to login as "syncuser" on the remote system without
 any password.
 You can try to remotely login by entering the following on the local system:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ssh -p 22 syncuser@remotesystem.tld
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Be aware that only the user that generated the ssh key can remotely log
 in.
\end_layout

\begin_layout Standard
You may optionnaly enhance remote login security by applying chapter 
\begin_inset CommandInset ref
LatexCommand ref
reference "subsec:Enhancing-remote-backup"

\end_inset

 methods.
\end_layout

\begin_layout Subsection
Mail transport agent
\end_layout

\begin_layout Standard
You should make sure your system can send emails so osync can warn you if
 something bad happens.
 osync will use mutt or mail command.
 Please make sure you can send a test mail with at least one of the following
 commands run by your sync user:
\end_layout

\begin_layout Standard
On Linux / BSD / MacOS / Windows 10 Bash
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ echo "your test message" | mutt -x -s "This is a test message" your@mail.tld
\end_layout

\begin_layout Plain Layout

$ echo "your test message" | mail -s "This is a test message" your@mail.tld
\end_layout

\end_inset


\end_layout

\begin_layout Standard
On termux (Android)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ echo -e"Subject:subject
\backslash
r
\backslash
nyour test message" |sendmail -f "sender@mail.tld" -S "smtp.yourisp.tld:25"
 -au"MySMTPUser" -ap"MySMTPPassword" "destination@mail.tld"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Check your antispam if you don't get your message.
 If you still don't get your message, check your distributions documentation
 about the mail command.
\end_layout

\begin_layout Standard
If you run on windows cygwin / msys environment, please make sure you can
 launch mailsend.exe / sendemail.exe by adding it to the %PATH% variable (found
 
\begin_inset CommandInset href
LatexCommand href
name "here"
target "http://github.com/muquit/mailsend"

\end_inset

 and 
\begin_inset CommandInset href
LatexCommand href
name "here"
target "http://caspian.dotconf.net/menu/Software/SendEmail/"

\end_inset

).
\end_layout

\begin_layout Subsection
\begin_inset CommandInset label
LatexCommand label
name "subsec:Enhancing-remote-backup"

\end_inset

Enhancing remote system security
\end_layout

\begin_layout Standard
You may want to secure a password-less ssh access by removing non necessary
 services offered by SSH.
 Edit the file ~/.ssh/authorized_keys created earlier on the remote system
 and add the following line in the beginning of the file:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Also, we may want to prevent any host except of our initiator replica system
 to passwordless connect.
 Add the following line:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

from=*.my.initiator.replica.server.domain.tld
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Your authorized_keys file should look like this:
\end_layout

\begin_layout Standard
\begin_inset listings
lstparams "breaklines=true"
inline false
status open

\begin_layout Plain Layout

from="*.mydomain.tld",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-
pty ssh-rsa yourkey== syncuser@host.tld
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
More security enhancing (not recommended unless you know what you are doing)
\end_layout

\begin_layout Standard
We may also restrict the ssh session to only a couple of commands we'll
 need.
 osync comes with a script called 
\emph on
ssh_filter.sh
\emph default
 that will only allow execution of commands osync needs.
 Once again edit your authorized_keys file and add the following.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

command="/usr/local/bin/ssh_filter.sh SomeAlphaNumericToken9"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Your file should then look like this:
\end_layout

\begin_layout Standard
\begin_inset listings
lstparams "breaklines=true,showstringspaces=false"
inline false
status open

\begin_layout Plain Layout

from="*.mydomain.tld",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-
pty,command="/usr/local/bin/ssh_filter.sh SomeAlphaNumericToken9" ssh-rsa
 yourkey== syncuser@remotesystem.tld 
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Copy then the script ssh_filter.sh to /usr/local/bin on the remote system.
 Don't forget to make it executable and make it owned by root
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

# chmod 755 /usr/local/bin/ssh_filter.sh
\end_layout

\begin_layout Plain Layout

# chown root:root /usr/local/bin/ssh_filter.sh
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Now, only the commands send by osync including a specific remote token may
 be executed via the ssh tunnel.
 You may enable / disable the usage of sudo command by editing the following
 value in the ssh_filter.sh script as well as in the osync config file:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SUDO_EXEC=yes
\end_layout

\end_inset


\end_layout

\begin_layout Subparagraph
The remote token can be set in the config file and must match the one setup
 in authorized_keys file.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

_REMOTE_TOKEN=SomeAlphaNumericToken9
\end_layout

\end_inset


\end_layout

\begin_layout Standard
You may also set it on the fly in quicksync mode with the parameter
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ osync.sh --remote-token=SomeAlphaNumericToken9
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
\begin_inset CommandInset label
LatexCommand label
name "subsec:More-security-(or"

\end_inset

Security for the paranoid (not recommended unless you really know what you
 are doing)
\end_layout

\begin_layout Standard
Executing rsync as superuser is a security risk.
 A way to prevent rsync usage allowing only a symlink to be executed.
 Thus, a attacker script using rsync would not work.
 This kind of security is called 
\begin_inset Quotes eld
\end_inset

security by obscurity
\begin_inset Quotes erd
\end_inset

 and should generally not be the only security process, but makes any attack
 harder.
 First, let's create a symlink to rsync called let's say o_rsync, on both
 local and remote systems.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

# ln -s $(type rsync) $(dirname $(type rsync))/o_rsync
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Now edit the osync config file and change the following value:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_EXECUTABLE=o_rsync
\end_layout

\end_inset


\end_layout

\begin_layout Section
Running osync
\end_layout

\begin_layout Subsection
Basics
\end_layout

\begin_layout Standard
Everytime osync is run, it runs with an INSTANCE_ID.
\end_layout

\begin_layout Standard
This INSTANCE_ID helps identifying successive runs on replicas, and helps
 differentiate concurrent runs of the same initiator replica to different
 targets.
\end_layout

\begin_layout Standard
By default, the INSTANCE_ID in quicksync mode is 
\begin_inset Quotes sld
\end_inset

quicksync_task
\begin_inset Quotes srd
\end_inset

.
 This might be overriden via command-line or by using a configuration file.
\end_layout

\begin_layout Standard
Keep in mind that two osync instances should never share the same INSTANCE_ID.
\end_layout

\begin_layout Subsection
\begin_inset CommandInset label
LatexCommand label
name "sec:Running-Osync-in"

\end_inset

Running osync in quicksync mode
\end_layout

\begin_layout Standard
You just osync to sync two local dirs like this:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ./osync.sh --initiator=/path/to/dir1 --target=/path/to/dir2
\end_layout

\end_inset


\end_layout

\begin_layout Standard
You also may want to sync a remote directory.
 
\end_layout

\begin_layout Standard
You may specify an alternate SSH port directly in the URI.
 When ommited, SSH port 22 is used.
\end_layout

\begin_layout Standard
Also, if not set, the default RSA key will be read from ~/.ssh/id_rsa
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ./osync.sh --initiator=/path/to/dir1 --target=ssh://remoteuser@remotehost.com//pa
th/to/dir2
\end_layout

\begin_layout Plain Layout

$ ./osync.sh --initiator=/path/to/dir2 --target=ssh://remoteuser@remotehost.com:22/
/path/to/dir2 --rsakey=/home/user/.ssh/other_key
\end_layout

\end_inset


\end_layout

\begin_layout Standard
The following command-line options are quicksync specific:
\end_layout

\begin_layout Standard
Use an RSA key to connect remotely
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--rsakey=/path/to/rsa.key
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Use a password file instead of an RSA key (needs sshpass utility installed)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--password-file=/path/to/passwd
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Set INSTANCE_ID
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--instance-id="some-instance-name"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Skip deletions on initiator, target or both (valid values are: initiator
 or target or initiator,target)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--skip-deletion=initiator,target
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Send alert emails (only works with Linux / BSD / Windows 10 bash / MacOSX
 in quicksync mode)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--destination-mails="my@mail.tld myother@mail.tld"
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Setting environment variables
\end_layout

\begin_layout Subsubsection
General environment variables
\end_layout

\begin_layout Standard
Quicksync mode actually can make use of most options available in config
 files.
\end_layout

\begin_layout Standard
You may set them on the fly as environment variable like
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ PRESERVE_ACL=yes ./osync.sh --initiator=/path/to/dir1 --target=/path/to/dir2
\end_layout

\end_inset


\end_layout

\begin_layout Standard
A list of config values is found in appendix.
\end_layout

\begin_layout Subsubsection
Special environment variables
\end_layout

\begin_layout Standard
There is a set of special environment variables used mainly for debugging
 purposes.
\end_layout

\begin_layout Standard
Valid ones are:
\end_layout

\begin_layout Standard
Enable deubgging
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

_DEBUG=yes
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Enable paranoid debugging (only works on debug_osync.sh build or bootstrap.sh)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

_PARANOIA_DEBUG=yes
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Increase / decrease sleeping time between process checks when osync waits
 for a process.
 Default value is 0.05.
 (x is an integer or floating point number)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SLEEP_TIME=x
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Ignore unknown OS and execute regardless with default options.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

IGNORE_OS_TYPE=yes
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
\begin_inset CommandInset label
LatexCommand label
name "sec:Running-Osync-with-config-file"

\end_inset

Running osync with a full blown configuration file
\end_layout

\begin_layout Standard
Running osync with a configuration will do just the same as in quicksync
 mode, except that you have much more control of what's going on.
\end_layout

\begin_layout Standard
A sample configuration file is called sync.conf and is included with osync.
 You may edit this file to fit your needs.
 Basically configuration files should go to /etc/osync.
\end_layout

\begin_layout Standard
Every option of the configuration file is explained in the appendix.
\end_layout

\begin_layout Standard
Once you've setup a file according to your needs, you may go for a test
 run.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ./osync.sh /etc/osync/my_sync.conf --dry --verbose
\end_layout

\end_inset


\end_layout

\begin_layout Standard
osync should enumerate which changes will be done on both sides.
\end_layout

\begin_layout Standard
If everything worked out right, you might process the actual sync process.
\end_layout

\begin_layout Standard
A full configuration file specifies a maximum execution delay.
 Initial sync tasks can take a huge amount of time depending on bandwidth
 between replicas, in that case you might add parameter –no-maxtime to your
 first sync run so execution time won't be enforced.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ./osync.sh /etc/osync/my_sync.conf --no-maxtime
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Creating a regular sync scenario is quite simple as long as you don't schedule
 twice the same sync task in a shorter time span than your HARD_MAX_EXEC_TIME_TO
TAL value.
 Just create a crontab entry and add parameter –silent so your local mailbox
 won't get filled up.
 Example, having a sync scheduled every hour in /etc/crontab
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

00 * * * * syncuser /usr/local/bin/osync.sh /etc/osync/your_sync.conf --silent
\end_layout

\end_inset


\end_layout

\begin_layout Subparagraph
Please note that this syntax works on RedHat / CentOS.
 On Debian you might need to remove the usename 
\begin_inset Quotes sld
\end_inset

ie syncuser
\begin_inset Quotes srd
\end_inset

 in order to make the crontab line work.
\end_layout

\begin_layout Standard
You may find the sync log under /var/log/osync-your_sync.log or under the
 current directory if /var/log is not writable.
\end_layout

\begin_layout Subsection
\begin_inset CommandInset label
LatexCommand label
name "sec:Running-Osync-as-daemon"

\end_inset

Running osync as deamon
\end_layout

\begin_layout Subsubsection
Manually
\end_layout

\begin_layout Standard
osync may also run in file monitor mode.
 In this mode, osync checks the initiator replica, and runs a synchronization
 as soon as there is file activity on initiator replica.
 With this mode, you do not need a schedule anymore.
 Be aware that only initiator replica is monitored, and target replica sync
 updates only occur when initiator replica modifications happen.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ./osync.sh /etc/osync/my_sync.conf --on-changes
\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
As a system service
\end_layout

\begin_layout Standard
If you plan to run osync on a regular basis in file monitor mode, you might
 consider installing it as a system service.
\end_layout

\begin_layout Standard
From the directory you downloaded osync, run the install.sh script and enable
 the service.
\end_layout

\begin_layout Standard
Remark: When exiting osync daemon, the process will continue to run for
 up to a minute to unlock replicas and termine sub processes.
\end_layout

\begin_layout Paragraph
init.d service files
\end_layout

\begin_layout Standard
For init.d systems, syntax is:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

# service osync-srv start
\end_layout

\begin_layout Plain Layout

# chkconfig osync-srv on
\end_layout

\end_inset


\end_layout

\begin_layout Standard
osync then scans for *.conf files in /etc/osync and will run an instance
 per configuration file.
\end_layout

\begin_layout Standard
Service control just works like with standard system services.
\end_layout

\begin_layout Paragraph
systemd service files
\end_layout

\begin_layout Standard
For systemd systems, syntax is:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

# systemctl start osync-srv@config_file
\end_layout

\begin_layout Plain Layout

# systemctl enable osync-srv@config_file
\end_layout

\end_inset


\end_layout

\begin_layout Standard
With systemd, every config file found in /etc/osync can be controlled as
 a separate service.
\end_layout

\begin_layout Standard
Note that on FreeBSD, rsync exclusion patterns won't work because if inotifywait
's limited –exclude implementation that can only make use of one exclude
 parameter.
\end_layout

\begin_layout Subsection
Modifying osync behavior
\end_layout

\begin_layout Subsubsection
Output / log behavior
\end_layout

\begin_layout Standard
On most runs, you may only want to output file modifications or errors.
 You may achieve this (in quicksync / conf / daemon modes) by adding the
 following parameters:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ ./osync.sh /path/to/sync.conf --errors-only --summary --no-prefix
\end_layout

\end_inset


\end_layout

\begin_layout Standard
The following is a list of all command line switches that work with all
 three modes:
\end_layout

\begin_layout Standard
Will run a simulation only
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--dry
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Silents osync totally, to be used in a cron schedule
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--silent
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Show a summary of updated / deleted files
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--summary
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Suppress non error state messages
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--errors-only
\end_layout

\end_inset


\end_layout

\begin_layout Standard
More detailled output (debug)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--verbose
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Suppress log time prefix
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--no-prefix
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Add rsync stats to output
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--stats
\end_layout

\end_inset


\end_layout

\begin_layout Subsubsection
Execution behavior
\end_layout

\begin_layout Standard
Disable HARD_MAX_EXEC_TIME checks, so that a synchronization can take as
 long as it wants.
 This is used to perfom initial sync operations on big sets of files
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--no-maxtime
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Override any existing active or dead locks on replicas.
 Be careful if there is another running sync on any of both replicas
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--force-unlock
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Invoke daemon like mode.
 Shouldn't actually be used unless for debugging.
 Use daemon service files instead.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--on-changes
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Show help
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--help
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Running osync batch
\end_layout

\begin_layout Standard
If you have multiple configuration files in /etc/osync that you would like
 to run sequentially, and re-run failed sync tasks, osync comes with a tool
 called osync-batch.
\end_layout

\begin_layout Standard
It will execute all osync conf files in a row, in a given timespan.
\end_layout

\begin_layout Standard
osync-batch passes all its parameters to osync itself, except for the following
 which modifiy batch behavior itself:
\end_layout

\begin_layout Standard
Path to directory containing osync configuration files
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--path=/etc/osync
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Maximum number of runs for failing synchronisation tasks (x is an integer).
 Defaults to 3.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--max-runs=x
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Maximum execution time for whole batch process in seconds (x is an integer).
 Defaults to 36000.
 Setting to 0 disables max execution time check.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

--max-exec-time=x
\end_layout

\end_inset


\end_layout

\begin_layout Standard
You may program a cron task for osync-batch.sh like
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

00 * * * * syncuser /usr/local/bin/osync-batch.sh --path=/etc/osync --silent
\end_layout

\end_inset


\end_layout

\begin_layout Section
System & FS Caveats
\end_layout

\begin_layout Standard
Depending on which configuration osync runs, not all functions may work.
\end_layout

\begin_layout Standard
Especially, ACL and entended attributes preservation won't work on MacOSX,
 Cygwin, MSYS, Android and BusyBox local or remote environments.
\end_layout

\begin_layout Standard
In order to work on most systems, ACL preservation and extended system attribute
 preservarion has been disabled in quicksync mode.
\end_layout

\begin_layout Standard
To enable them, please run osync with the following environment variables
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ PRESERVE_ACL=yes PRESERVE_XATTR=yes ./osync.sh
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Those settings are also valid if set in config files.
\end_layout

\begin_layout Standard
Also, setting up a sync between different file systems may prevent certain
 functionnality to work (mainly ACL preservation, extended attribute preservatio
n and symlink / hardlink support).
\end_layout

\begin_layout Standard
At last, MSYS2 has symlink support disabled by default.
 It can be enabled by uncommenting MSYS=winsymlinks:nativestrict in msys2-shell.c
md, but doesn't behave exactly like other implementations.
\end_layout

\begin_layout Section
Configuration file appendix
\end_layout

\begin_layout Subsection
Full list of configuration file parameters
\end_layout

\begin_layout Standard
Set this to whatever you want to identify your sync task.
 Two different osync runs should never share the same INSTANCE_ID.
 This value also determines the log filename and appears in the warning
 / error mails.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

INSTANCE_ID=name_of_your_sync
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Initiator directory to sync (initiator replica), must be on the system you're
 running osync on.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

INITIATOR_SYNC_DIR="/some/path"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Target directory to sync (target replica), can be on the same system you're
 running osync on or another remote system, reachable via an SSH tunnel.
\end_layout

\begin_layout Standard
Target directory can be a SSH uri like 
\begin_inset Quotes sld
\end_inset

ssh://user@host.com:1234//some/other/path
\begin_inset Quotes srd
\end_inset

 where 1234 is an optional port, and the first slash is a separator, meaning
 that the full path is /some/other/path.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

TARGET_SYNC_DIR="/some/other/path"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Location of the private RSA key.
 If left empty, the default path 
\begin_inset Quotes sld
\end_inset

~/.ssh/id_rsa
\begin_inset Quotes srd
\end_inset

 will be used.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SSH_RSA_PRIVATE_KEY=~/.ssh/id_rsa
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Alternate auth method by using a password file.
 This needs sshpass to be installed.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SSH_PASSWORD_FILE=/home/syncuser/path/to/passwd
\end_layout

\end_inset


\end_layout

\begin_layout Standard
When using ssh_filter security, you need to specify a remote token matching
 the one setup in remote authorized_keys file
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

_REMOTE_TOKEN=SomeAlphaNumericToken9
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Tells osync to create initiator or target directories if they don't exist.
 Default is no.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

CREATE_DIRS=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
By default, leaving this empty sets the log file to /var/log/osync_INSTANCE_ID.lo
g or ./osync_INSTANCE_ID.log if /var/log is not writable.
 You might change this to specify a personalized log file.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

LOGFILE=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Generate an alert if initiator or target replicas have less space than the
 following given value in kilobytes.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

MINIMUM_SPACE=10240
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Bandwidth limit in kilobytes / second.
 Leave this to zero to disable limitation.
 Note that bandwidth is enforced only when running file updates.
 All other sync steps don't enforce that setting as they generally need
 very little bandwidth.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

BANDWIDTH=0
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Synchronization tasks may be executed as root if you enable the following
 parameter.
 See prerequisites in chapter 
\begin_inset CommandInset ref
LatexCommand ref
reference "subsec:Performing-superuser-backups"

\end_inset

.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SUDO_EXEC=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Paranoia option.
 Don't change this unless you read chapter 
\begin_inset CommandInset ref
LatexCommand ref
reference "subsec:More-security-(or"

\end_inset

 and understand what you are doing.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_EXECUTABLE=rsync
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Remote Rsync Executable path.
 Don't change this unless your remote rsync binary isn't in the execution
 path.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_REMOTE_PATH=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Rsync include / exclude order.
 If set to include, includes will be processed before excludes, and vice-versa.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_PATTERN_FIRST=include|exclude
\end_layout

\end_inset


\end_layout

\begin_layout Standard
List of files / directories to include / exclude from both replicas (see
 rsync patterns for more explanations, wildcards won't work).
\end_layout

\begin_layout Standard
Poaths are relative to both replicas.
 List is separated by PATH_SEPARATOR_CHAR defined below.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_INCLUDE_PATTERN=""
\end_layout

\begin_layout Plain Layout

RSYNC_EXCLUDE_PATTERN="tmp;archives;somepath"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
File that contains the list of files /directories to include / exclude from
 both replicas (see rsync pattern files for more explanations).
 Leave this empty if you don't want to use an exclusion file.
 This file has to be in the same directory as the config file.
 Paths are relative to sync dirs.
 One element per line.
 
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_INCLUDE_FROM=""
\end_layout

\begin_layout Plain Layout

RSYNC_EXCLUDE_FROM="exclude.list"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Path separator char for RSYNC_EXCLUDE_PATTERN, you might change this in
 the unholy case that your filenames contains semicolons.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PATH_SEPARATOR_CHAR=";"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Enable / disable ssh compression.
 Leave this enabled unless your connection to remote system is high speed
 (LAN)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SSH_COMPRESSION=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Tell ssh to not check the remote computer ssh fingerprint.
 DANGER WILL ROBINSON ! This should generally lead to security issues.
 Only enable this if you know exactly what you are doing.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SSH_IGNORE_KNOWN_HOSTS=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Ping remote host before launching synchronization.
 Be sure the host is responding to ping.
 Failing to ping will skip current task.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

REMOTE_HOST_PING=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Itemize
Check for internet access by pinging one or more hosts before launching
 remote sync task.
 Leave this empty do disable the checks.
 Failed checks won't abort current task, just trigger a warning.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

REMOTE_3RD_PARTY_HOST="www.kernel.org www.google.fr"
\end_layout

\end_inset


\end_layout

\begin_layout Itemize
Misc settings
\end_layout

\begin_layout Standard
Optional arguments to pass to rsync.
 Do not use already managed parameters by rsync (-r -l -p -t -g -o -D -E
 - u- i- n --executability -A -X -L -K -H -8 -zz –skip-compress –checksum
 –bwlimit –partial –partial-dir –no-whole-file –whole-file –backup –backup-dir
 –suffix --exclude --exclude-from --include --include-from --list-only --stats)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_OPTIONAL_ARGS=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Should osync preserve standard unix permissions
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_PERMISSIONS=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Should osync preserve file owner
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_OWNER=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Should osync preserve group owner
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_GROUP=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Should osync preserve files executability status
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_EXECUTABILITY=yes|no
\end_layout

\end_inset

Preserve ACLs.
 Please check that your filesystem supports ACLs and is mounted with it's
 support or rsync will get you loads of errors.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_ACL=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Preserve Xattr.
 The same applies as for ACLs
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_XATTR=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Transforms symlinks into referent files/dirs when syncing replicas.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

COPY_SYMLINKS=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Treat symlinked dirs as dirs.
 CAUTION: This also follows symlinks outside of the replica root.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

KEEP_DIRLINKS=no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Preserve hard links.
 Make sure source and target FS can manage hard links or you will lose them.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PRESERVE_HARDLINKS=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Do a full checksum on files instead of comparing file sizes and modification
 times.
 Enabling this will make sync tasks longer.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

CHECKSUM=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Use rsync compression for file transfers.
 Leave this disabled unless your're not using SSH compression.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RSYNC_COMPRESS=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Maximum execution time (in seconds) for sync process.
 Soft value generates a warning only.
 Hard value generates a warning and stops sync task.
\end_layout

\begin_layout Standard
You may set this to 0 to disable time checks.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SOFT_MAX_EXEC_TIME_FILE_TASK=7200
\end_layout

\begin_layout Plain Layout

HARD_MAX_EXEC_TIME_FILE_TASK=10600
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Log a status message every KEEP_LOGGING seconds.
 Set this to zero to disable status messages.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

KEEP_LOGGING=1801
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Minimum time (in seconds) in file monitor /daemon mode between modification
 detection and sync task in order to let copy operations finish.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

MIN_WAIT=60
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Maximum time (in seconds) in file monitor / daemon mode.
 After this amount of time, a sync operation is forced.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

MAX_WAIT=7200
\end_layout

\end_inset


\end_layout

\begin_layout Itemize
Conflict and deletion option
\end_layout

\begin_layout Standard
Enabling this option will keep a backup of a file on the target replica
 if it gets updated from the source replica.
 Backups will be made to .osync_workdir/backups
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

CONFLICT_BACKUP=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Keep multiple backup versions of the same file.
 Warning, This can be very space consuming.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

CONFLICT_BACKUP_MULTIPLE=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
osync will clean backup files after a given number of days.
 Setting this to 0 will disable cleaning and keep backups forever.
 Warning: This can be very space consuming.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

CONFLICT_BACKUP_DAYS=30
\end_layout

\end_inset


\end_layout

\begin_layout Standard
If the same file exists on both replicas, newer version will be synced.
 However, if both files have the same timestamp but differ, CONFLICT_PREVALANCE
 sets winner replica.
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

CONFLICT_PREVALANCE=initiator|target
\end_layout

\end_inset


\end_layout

\begin_layout Standard
On deletition propagation to the target replica, a backup of the deleted
 files can be kept.
 Deletions will be kept in .osync_workdir/deleted
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SOFT_DELETE=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
osync will clean deleted files after a given number of days.
 Setting this to 0 will disable cleaning and keep deleted files forever.
 Warning: This can be very space consuming.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SOFT_DELETE_DAYS=30
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Deletion propagation (not soft deletion) can be skipped on one or both replicas.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SKIP_DELETION=initiator|target|initiator,target
\end_layout

\end_inset


\end_layout

\begin_layout Itemize
Resuming options
\end_layout

\begin_layout Standard
Try to resume an aborted sync task
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RESUME_SYNC=yes|no
\end_layout

\end_inset

 Number maximum resume tries before initating a fresh sync.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RESUME_TRY=2
\end_layout

\end_inset


\end_layout

\begin_layout Standard
When a pidlock exists on target replica that does not correspond to initiator's
 instance-id, force pidlock removal.
 Be carefull with this option if you have multiple initiators.
\end_layout

\begin_layout Standard
\begin_inset listings
lstparams "breaklines=true"
inline false
status open

\begin_layout Plain Layout

FORCE_STRANGER_LOCK_RESUME=no
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Keep partial uploads that can be resumed on next run.
 This can be very useful if big files must get updated though slow links.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

PARTIAL=no 
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Use rsync delta copy algorithm.
 Disabling this is useful to reduce CPU usage and raise bandwidth which
 might be valuable on local-local syncs or LAN syncs.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

DELTA_COPIES=yes
\end_layout

\end_inset


\end_layout

\begin_layout Itemize
Alert Options
\end_layout

\begin_layout Standard
Optional mail body encoding (using iconv).
\end_layout

\begin_layout Standard
By default, all mails are sent in UTF-8 format without header (because of
 maximum compatibility of all platforms).
 You may specify an optional encoding here (like "ISO-8859-1" or whatever
 iconv can handle)
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

MAIL_BODY_CHARSET=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
List of alert mails separated by spaces
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

DESTINATION_MAILS="your@alert.tld"
\end_layout

\end_inset


\end_layout

\begin_layout Standard
MSYS / Cygwin / Android / Busybox only mail options
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

SENDER_MAIL="alert@your.system.tld"
\end_layout

\begin_layout Plain Layout

SMTP_SERVER=smtp.your.isp.tld
\end_layout

\begin_layout Plain Layout

SMTP_PORT=25
\end_layout

\begin_layout Plain Layout

SMTP_ENCRYPTION=tls|ssl|none
\end_layout

\begin_layout Plain Layout

SMTP_USER=optional_smtp_user
\end_layout

\begin_layout Plain Layout

SMTP_PASSWORD=optional_smtp_password
\end_layout

\end_inset


\end_layout

\begin_layout Itemize
Execution hooks
\end_layout

\begin_layout Standard
Commands can will be run before and / or after sync process (remote execution
 will only happen if REMOTE_SYNC is set).
 Multiple commands can be semicolon separated.
\end_layout

\begin_layout Standard
Command(s) to run locally before sync process starts.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

LOCAL_RUN_BEFORE_CMD=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Command(s) to run locally if sync process finishes.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

LOCAL_RUN_AFTER_CMD=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Command(s) to run on remote system before sync process starts.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

REMOTE_RUN_BEFORE_CMD=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Command(s) to run on remote system if sync process finishes.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

REMOTE_RUN_AFTER_CMD=""
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Max execution time of commands before they get force killed.
 Leave 0 if you don't wan't this to happen.
 Time is specified in seconds.
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

MAX_EXEC_TIME_PER_CMD_BEFORE=0 
\end_layout

\begin_layout Plain Layout

MAX_EXEC_TIME_PER_CMD_AFTER=0
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Stops osync execution if one of the above commands fail
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

STOP_ON_CMD_ERROR=yes|no 
\end_layout

\end_inset


\end_layout

\begin_layout Standard
Run local and remote commands after a sync task even if it failed.
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

RUN_AFTER_CMD_ON_ERROR=yes|no
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Upgrades from v1.0x and v1.1x
\end_layout

\begin_layout Standard
Upgrades from osync v1.0x require to rewrite osync config file and state
 filenames.
 Master & slave replica are now called initiator and target replicas.
 SYNC-ID is now called INSTANCE-ID.
\end_layout

\begin_layout Standard
There's an update script that does this job.
\end_layout

\begin_layout Standard
For quicksync tasks:
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
status open

\begin_layout Plain Layout

$ upgrade-v1.0x-v1.2x.sh --master=/path/to/master/replica --slave=/path/to/slave/re
plica --sync-id=[INSTANCE_ID]
\end_layout

\end_inset


\end_layout

\begin_layout Standard
For config file tasks:
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\begin_layout Plain Layout

$ upgrade-v1.0x-v1.2x.sh /etc/osync/sync.conf
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\end_inset


\end_layout

\begin_layout Standard
Upgrades from osync v1.1x require to add osync configuration values into
 config file.
\end_layout

\begin_layout Standard
Just use the upgrade script the same way you would to upgrade from v1.0x.
\end_layout

\begin_layout Section
Troubleshooting
\end_layout

\begin_layout Standard
osync has been tested successfully on multiple systems for a wide variety
 of sync plans.
 Please check the following steps before requesting help.
\end_layout

\begin_layout Standard
If no error message is shown in console, please check the log files.
\end_layout

\begin_layout Subsection
Log files
\end_layout

\begin_layout Standard
Default [log_path] is /var/log, /home, ./ and /tmp depending if the directories
 are writable.
\end_layout

\begin_layout Standard
Everything that is printed on screen via stdout or stderr is always included
 in log file which is named osync.[INSTANCE_ID].log
\end_layout

\begin_layout Standard
Disabling switches like –errors-only or –silent may help diagnostic the
 problem.
\end_layout

\begin_layout Standard
Log inludes a prefix (normally TIME) which indicates since how much seconds
 osync runs.
\end_layout

\begin_layout Standard
When some commands get run remotely it will indicate how much seconds osync
 runs a specific remote task, beginning from 0 at every remote task.
\end_layout

\begin_layout Standard
Prefix can be disabled via a command line argument.
\end_layout

\begin_layout Subsection
Warnings, errors and alerts
\end_layout

\begin_layout Standard
osync has two levels of alerts.
\end_layout

\begin_layout Standard
Warnings are raised when something minor goes wrong, like checking for minimum
 available space or checking for internet connectivity, which will not affect
 the synchronization task directly.
\end_layout

\begin_layout Standard
Errors are raised when something happens that could possibily stop sync
 from happening.
\end_layout

\begin_layout Standard
Both are logged, and if email support is set, an alert email will be sent.
\end_layout

\begin_layout Subsection
Local-local sync
\end_layout

\begin_layout Standard
osync logs every of it's actions to [log_path]/osync-version.instance_id.log.
\end_layout

\begin_layout Standard
Please check the log file if something went wrong.
\end_layout

\begin_layout Standard
You might try running osync as root to check if your problem is filesystem
 permission related.
\end_layout

\begin_layout Standard
You might add –verbose option to see what actually happens.
\end_layout

\begin_layout Standard
Also, running osync with the following command will give the exact commands
 that actually happen:
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\begin_layout Plain Layout

$ DEBUG=yes /usr/local/bin/osync.sh /etc/osync/my_sync.conf --verbose
\end_layout

\end_inset


\end_layout

\begin_layout Subsection
Local-remote sync
\end_layout

\begin_layout Standard
Remote synchronization is a bit more tricky.
\end_layout

\begin_layout Standard
You might check that you can log in remotely with the command
\end_layout

\begin_layout Standard
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\begin_layout Plain Layout

$ ssh -p 22 remotesyncuser@remotehost.tld
\end_layout

\end_inset

Also, you might check that you can use rsync command remotely
\end_layout

\begin_layout Standard
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inline false
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\begin_layout Plain Layout

$ ssh -p 22 remotesyncuser@remotehost.tld rsync --help
\end_layout

\end_inset

You can temporarily disable ssh security by removing lines you added in
 chapter 
\begin_inset CommandInset ref
LatexCommand ref
reference "subsec:Enhancing-remote-backup"

\end_inset

.
 Additionnaly, you can check ssh_filter log in ~/.ssh/ssh_filter.log on the
 remote system.
 You might try running osync with SUDO_EXEC to check if your problem is
 user permission related.
\end_layout

\begin_layout Subsection
File monitor mode
\end_layout

\begin_layout Standard
In file monitor mode, osync will still log it's execution to /var/log/osync.insta
nce_id.log (or current directory if /var/log is not writable).
\end_layout

\begin_layout Standard
Also, standard systemd log method is used if available.
 You may check an execution with
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
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\begin_layout Plain Layout

# systemctl status osync-srv@configfile
\end_layout

\end_inset


\end_layout

\begin_layout Standard
You mai also see osync logs in journalctl with
\end_layout

\begin_layout Standard
\begin_inset listings
inline false
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\begin_layout Plain Layout

# journalctl -xn
\end_layout

\end_inset


\end_layout

\begin_layout Section
Final words
\end_layout

\begin_layout Standard
The idea of osync came in a discussion around a beer one evening.
 It began as a project for a friend, whose company I was working for as
 a consultant.
\end_layout

\begin_layout Standard
Today, osync is still used by this company, and a lot of others around the
 globe.
\end_layout

\begin_layout Standard
I do provide technical help and support in my spare time, and will appreciate
 every contribution on Github :)
\end_layout

\begin_layout Standard
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LatexCommand rule
offset "0.5ex"
width "100col%"
height "1pt"

\end_inset


\end_layout

\end_body
\end_document