Deleting oldest files to free space as needed on Linux

Question

I have a cron job that writes logs to /tmp. I want to automatically delete the oldest files when the free space in the disk becomes less than 1GB.

I'm trying to do df -ah /tmp, then take the 2nd line, use cut to get the avail column. Then in a for loop, keep deleting the files older than n days with -mtime until there's enough free space.

I probably want to set this up as a cron job that runs daily as well.

Solution

Instead of a find -mtime, do an ls -t, for example:

DIR=/tmp
FREESPACE=1000000
find $DIR -type f | xargs ls -1rt | while read f ; do
  if [ `df --output=avail $DIR | tail -1` -ge $FREESPACE ] ; then
    break
  fi
  # rm -f $f
done

Uncomment the rm -f $f to have it actually work...

However, I typically would do things a little differently. I'd put my cron logs in /var/log and let something like logrotate handle managing disk space. Or as another alternative, I'd put the logs into a separate subdirectory such as /tmp/mycronjob/*, and then keep a fixed number of days of log files. It's not as flexible as monitoring disk space, but it's also a straight forward find /tmp/mycronjob -mtime +30 -exec rm {} \; and more predictable.

Comments

[Morgan Christiansson]

I think the rm -f should be after the conditional. Otherwise it will always delete at least 1 directory even if there's enough available space.

[TOertel]

@MorganChristiansson true.

[Kamil Maciorowski]

Parsing ls is flawed in general.