If you're going to do this, you need to deal with the possibility that the script will die unceremoniously, leaving the lock file behind. This adds a trap, makes the lock file identify the machine, PID, and date/time the lock was asserted, and examines that information and attempts to determine whether the lock is really valid rather than blindly assuming that it is.
* #!/bin/bash Lock=**/some-where/rsync-is-running* *Log=**/some-where/rsync.log* *if [ -f $**Lock** ] then read <$**Lock** Machine PID RDate if [ `uname -n` = "$Machine" ] then if [ "x`ps -ocmd= -p $PID`" = "x$0" ] then echo "`date` - An instance of rsync is already running on this server: `ps -fp $PID`" >>$Log exit else echo "`date` Ignoring invalid lock entry: `cat **$**Lock**`" fi #[ "x`ps -ocmd= -p $PID`" = "x$0" ] else echo "`date` - An instance of rsync appears to be already running on $Machine: `cat **$**Lock**`" >>**$Log* * exit fi #[ `uname -n` = "$Machine" ] fi #**[ -f $**Lock** ] # If we make it this far, actually do it. **echo "`date` - Starting synchronization" >> **$Log**trap 'rm **$**Lock**; exit' 1 2 3 4 5 6 7 8 10 11 12 13 14 15 echo `uname -n` $$ `date` >**$**Lock* *# ... your script here ... echo "`date` - Finished synchronization" >> **$Log* *rm **$**Lock*
You could probably even use rcmd to validate the alleged PID of the process on the other machine, if you wanted to go to the trouble. Or just have one server be the designated initiator of the rsync, which simplifies things greatly.