Update flashing_os.md

pages/flashing_os.md

@@ -53,5 +53,11 @@ Decompress and flash image and follow to the [final steps](#the-final-steps). Be
     # pacman -Syu
     # reboot
     ```
+    
+6. **27.08.2020 note about update**: the latest version of Arch Linux has a slightly broken systemd. The problem is that the SSH login to your Pi-KVM may not work the first time, but the second or third. This issue does not affect the core functionality of Pi-KVM and will be fixed by Arch developers in the near future. However, if you want, you can use a temporary workaround for this problem:
+    * Switch OS to RW-mode: `rw`
+    * Edit file `/etc/pam.d/system-login` and comment line `-session   optional   pam_systemd.so` (prepend `#` character at the beginning).
+    * Perform `reboot`.
+    This will also disable some systemd and logind features that are not critical for Pi-KVM. If you do this, make yourself a reminder to uncomment this line in a couple of months.
 
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