no email sent, if /tmp is on NFS

[joluxer]

Hi Jim,
I've hunted down a problem that was an issue at my systems for more than a year now.
I run all my systems with NFS root, but only some systems put their /tmp on tmpfs or a local drive.

Since the last big system update about a year ago, where also dcron was replaced with a newer version, some systems did'nt send email from cron jobs any more. Today I inspected this problem and could show, that the problem occurs on my systems only, if the /tmp is on NFS.

My systems run Gentoo, the package I am testing with is dcron-4.5-r1, which contains dillon's cron daemon 4.5, kernel is 4.11 with aufs patch, email system ist postfix.

Symptoms are:

• cron jobs run fine and in time
• stderr and stdout is collected in temporary file (I could see this)
• when job is finished, email handler is not invoked (sendmail call is not seen, with supplied email handler -M switch also no invocation seen), thus no email is sent

Please feel free, to ask more questions about runtime environment or more tests.

Best regards, JLO