panic: unable to acquire file lock about docker-volume-backup HOT 7 CLOSED

An alternative syntax for your use case would be something like 0 0,12 * * *

from docker-volume-backup.

This looks as if your setup somehow triggers two concurrent invocations of the backup procedure and the second invocation fails because it cannot acquire the exclusive lock that guarantees no concurrent invocations are happening.

My initial suspicion would be that Busybox's cron does not like your cron expression, but then again, I'm not sure why, docs themselves are rather stiff lipped:

crontab
crontab [-c DIR] [-u USER] [-ler]|[FILE]

        -c      Crontab directory
        -u      User
        -l      List crontab
        -e      Edit crontab
        -r      Delete crontab
        FILE    Replace crontab by FILE ('-': stdin)

Could you try using a super simple cron expression like 0 12 * * * and check whether the issue persists?

from docker-volume-backup.

Thanks, I'll try to use the latter (0 0,12 * * *) and I'll let you know in a couple of days

from docker-volume-backup.

I confirm, It's working : (0 0,12 * * *)

from docker-volume-backup.

Good to know and thanks for the feedback. I'll add a note to the README about the cron syntax being limited in strange ways.

from docker-volume-backup.

So it seems busybox should support the syntax you have been using:

/ # crontab -l
# do daily/weekly/monthly maintenance
# min   hour    day     month   weekday command
*/15    *       *       *       *       run-parts /etc/periodic/15min
0       *       *       *       *       run-parts /etc/periodic/hourly
0       2       *       *       *       run-parts /etc/periodic/daily
0       3       *       *       6       run-parts /etc/periodic/weekly
0       5       1       *       *       run-parts /etc/periodic/monthly

which makes me wonder if someone expands that * in the expression when creating the crontab entry. I'll need to do some further investigation on this.

from docker-volume-backup.

It seems this is caused by the 00 in your example. Not sure why, but I cannot repro the issue when using single 0s in any way.

from docker-volume-backup.