Hi Hector,
Thanks for the detailed setup. To help you get closer to what we're seeing,
here's a more complete picture of our environment — the complexity is likely
why
your simpler setup doesn't reproduce it.
Our configuration:
- Ubuntu 24.04, autofs 5.1.9-1ubuntu4.1
- The autofs service runs under systemd with LimitNOFILE=524288 (not the
default
20480 shell ulimit — this matters for how long accumulation takes before
symptoms
appear)
- We have 25+ indirect autofs maps, all backed by LDAP (ldap:ou=...): /home,
/group, /proj, /tool, /build, /regres, /public, /archive, /devl, /products,
/hardwire, /wrk, /web, and a dozen more project-specific maps
- Each LDAP map contains many entries — hundreds in the case of /home and
/proj
- Map timeout is 900 seconds
How we observe the leak:
The fd count is only visible as root — /proc/<pid>/fd for the automount
daemon is
not readable by unprivileged users:
pid=$(systemctl show autofs --property=MainPID --value)
ls /proc/$pid/fd | wc -l
On a freshly restarted autofs we see ~80 fds. Over days of normal user
activity
on a compute host, this climbs gradually. We alert at 75% of LimitNOFILE
(~393K
fds) and treat 90% (~471K) as critical.
Our workaround:
Weekly systemctl restart autofs via cron, which resets the count instantly.
This
is what triggered the bug report — we needed to understand why we had to do
this.
What I'd leave to your expertise:
The core question is what lookup pattern drives the accumulation — whether
it's
the volume of unique indirect map entries accessed, failed mount attempts,
rapid
mount/expire cycling, or something in the LDAP map resolution path. You'll
know
better than I do which of those to stress first given the autofs 5.1.9
codebase.
Happy to provide strace output from an affected host, the exact fd breakdown
by
type (ls -la /proc/$pid/fd | grep socket etc.), or packet captures if any of
that
would help narrow down the code path.
Thanks again.
Marc
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https://bugs.launchpad.net/bugs/2152277
Title:
automount leaks Unix socketpairs per mount helper invocation — fd
exhaustion after days/weeks of uptime
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