Linux – When are files from /tmp deleted

On CentOS 6, it would seem that tmpwatch is basing it's decision to delete on when a file was last accessed (atime). If it's been 10 days (10d) or more then it will be deleted when tmpwatch runs.

From the tmpwatch man page:

    By  default,  tmpwatch  dates  files  by their atime (access time), not 
    their mtime (modification time). If files aren't being removed when 
    ls -l implies they should be, use ls -u to examine their atime to see if 
    that explains the problem.

Also from the man page:

    The time parameter defines the threshold for removing files.  If the
    file has not been accessed for time, the file is removed.  The time 
    argument is a number with an optional single-character suffix specifying 
    the units: m for minutes, h for hours, d for days.  If no  suffix  is 
    specified, time is in hours.

One solution would be to use a @reboot cron job:

@reboot mkdir -p "/tmp/$USER"

Adding this to your crontab with crontab -e would make it execute whenever the machine boots up.

Or, use

mkdir -p "/tmp/$USER"

in your shell's startup file.

In either case, you may also want to use

TMPDIR=/tmp/$USER
export TMPDIR

in your shell's startup file if you want to use that directory as the default temporary directory.