If you can afford the time to wait whatever time it takes before your system gets in sync, you can use the ntp-waitntp-wait command:
ntp-wait || exit -1
# i believe this would exit the script if it fails, but not sure of ntp-wait return codes, learn this first.
echo Time is synced, go ahead with backup
tar
rsync etc.
ntp-wait || exit -1
# i believe this would exit the script if it fails, but not sure of ntp-wait return codes, learn this first.
echo Time is synced, go ahead with backup
tar
rsync etc.
