How recover deleted crontab (-r option)

Question

I have deleted my crontab using crontab -r command ( r and e are so close on keyboard and there wasn't question sort of Are you sure? [Y/n] .

Its funny, you must use -i option to enable this question - should be enabled by default:-)

My crontab records are definitely lost or there is some backup file, how can I recover it?

Thank you.

Answer 1

I faced the same issue but I had edited the crontab file several times before pressing crontab -r, so I could find the previous versions in tmp directory. So try your luck looking into your tmp directory once.

Answer 2

If you are lucky and this happend fairly recent, you might find it in

/tmp/crontab.<unique_identifier>/crontab

This is a copy of your previous crontab. You can simply copy and paste it to get your cronjobs back

Answer 3

Unfortunately, the crontab mechanism does not provide a way to recover deleted or earlier versions of your crontab file. That being said, it is always worth tracing the following steps:

1. Check lingering temporaries: When you edit a crontab file, you make use of an editor. By default, this is vi , but it could also be the one defined by the variables EDITOR or VISUAL . Depending on the settings of those editors and your handling, you might have lingering backup files laying around. These could be of the form filename~ or #filename or anything else. Check files that could represent backups of _PATH_TMP/crontab.XXXXXXX . The value of _PATH_TMP is defined in /usr/include/paths.h . If that file does not exist, it defaults to /tmp . Be aware that /tmp is wiped at every reboot of your system.
2. Check filesystem snapshots or clones: Crontab stores user crontab files in an implementation-dependent location. By default this is /var/cron/tabs/$USER but it could also be /var/spool/cron/$USER or anything else. Check man crontab to disclose the location. There will never be a backup file there. However, your system might have a filesystem that has snapshots or clones configured. These are read-only copies of the filesystem taken at a moment in time. Think of it as a backup on the file system itself. From the more classic filesystems (ext4, ...) BTRFS, OCFS2 and ZFS support snapshots.
3. Check actual backups: Maybe you are in luck and your system-administrator made backups for you.

Beyond these 3 possibilities, I do not see a way how you could recover your crontab.

The most important thing you should do is to let cron backup your crontab file. You could do this hourly using:

# Example of job definition:
# .----------------- minute (0 - 59)
# |  .------------- hour (0 - 23)
# |  |  .---------- day of month (1 - 31)
# |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7)
# |  |  |  |  |
# *  *  *  *  *   command to be executed
  0  *  *  *  *   crontab -l > tmp/crontab.bck

Obviously, you can make it more intelligent with a script, but this would already satisfy your bare needs.