1.sh

$ ls -alR /etc/gdm3/
/etc/gdm3/:
total 24
drwxr-xr-x   4 root root  4096 Jun  2 01:45 .
drwxr-xr-x 135 root root 12288 Jun  2 01:43 ..
drwxr-xr-x   2 root root  4096 Jun  2 01:45 Init
drwxr-xr-x   2 root root  4096 Jun  2 01:45 PostLogin

/etc/gdm3/Init:
total 12
drwxr-xr-x 2 root root 4096 Jun  2 01:45 .
drwxr-xr-x 4 root root 4096 Jun  2 01:45 ..
-rw-r--r-- 1 root root  162 Jun  2 01:45 Default

/etc/gdm3/PostLogin:
total 12
drwxr-xr-x 2 root root 4096 Jun  2 01:45 .
drwxr-xr-x 4 root root 4096 Jun  2 01:45 ..
-rwxr-xr-x 1 root root   77 Jun  2 01:45 Default

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

$ cat /etc/gdm3/Init/Default
/usr/bin/killall synergyc
while [ $(pgrep -x synergyc) ]; do sleep 0.1; done
/usr/bin/synergyc -f --no-tray --debug INFO --name user-pc 192.168.x.x:24800
exit 0

$ cat /etc/gdm3/PostLogin/Default
/usr/bin/killall synergyc
while [ $(pgrep -x synergyc) ]; do sleep 0.1; done