Crontab deleted?

crontab with no arguments reads a crontab file from standard input. For example, you might use:

 echo "* * * * *  run-this-every-minute" | crontab

Once you've clobbered your crontab (i.e., crontab -l shows nothing), there's no good way to get it back.

On my system (Ubuntu 11.04), personal crontabs are stored in /var/spool/cron/crontabs/<USER> -- but that's what you clobbered, so that won't do you any good. (The path could be different on your system.)

I see entries in /var/log/syslog for commands executed by cron; you might be able to reconstruct your crontab from that (or your system's equivalent, if any), but it's going to be tedious.

Here's what I do to avoid this kind of problem:

I keep my crontab in a separate file, maintained in a source control system. I install it only by running

crontab filename

I never use crontab -e. If I accidentally clobber my crontab, I can just reload it from the file. (Well, hardly ever; I sometimes use crontab -e to make temporary changes, knowing that I can restore the current version later.)

Script for full crontab recovery

I made a PHP script that does a full recovery of your crontab, based on the log.

It outputs a single instance of every cron command run by the user for the last week.

I put it here

https://github.com/dangreenisrael/recover_crontab

Here is a sample output:

perl ~/sorttv/sorttv.pl

/usr/local/bin/flexget

bash ~/scripts/sort_sports.sh

~/scripts/play_recently_added.sh