How-to clean your /tmp when mysql tmp is full

1. Install tmpwatch if it’s not installed. If you run this command when tmpwatch is already installed and on the latest version, it will tell you there is nothing to do and no harm will be caused.

yum install tmpwatch

2. Check how many files are in /tmp

ls -1 /tmp | wc -l

3. Run tmpwatch to clear the /tmp partition of files over a week old now:

tmpwatch --mtime --all 168 /tmp

4. Check to see if some files were actually removed from /tmp.  If not, decrease the number of hours (in this case 168) until enough files are removed to give sufficient space in /tmp.  Do not lower the number below 12. 

ls -1 /tmp | wc -l

5. Add tmpwatch to root’s crontab to clear old files (more than a week old) every night.  If you needed to lower the number of hours in step 3, lower it here as well.  For more information on editing the crontab,

crontab -e

0 0 * * * tmpwatch --mtime --all 168 /tmp