Dear Maintainer,

dhcpcd 10.5.2 no longer points stdout/stderr at /dev/null when it
daemonises. Any caller that reads dhcpcd's output through a pipe
therefore hangs forever, even though the lease is applied. 10.3.2 is
not affected.

Reproducer:

  dhcpcd --ipv4only --waitip --persistent --noarp eth0 | cat

With 10.5.2 this never returns, and /proc/<pid>/fd/{1,2} of the daemon
still point to the pipe.

Cause: upstream commit 62018896 made setrlimit(RLIMIT_NOFILE, {0,0}) in
ps_dropprivs() unconditional. On Linux, dup2() onto fds 1/2 then fails
with EBADF, and dhcpcd_daemonised() ignores the error.

Known affected callers:
 - cloud-init ephemeral DHCP: waits until its 300s timeout, slowing
   boot (upstream #737)
 - netplan.io autopkgtest "wifi" (subprocess.check_output on
   dhcpcd -w), which now hangs until the timeout in Ubuntu:
https://autopkgtest.ubuntu.com/packages/n/netplan.io/stonking/amd64
 - sysvinit setups where rc scripts wait on the console (upstream #716)

Upstream fix (open PR, not merged yet):
https://github.com/NetworkConfiguration/dhcpcd/pull/733

Please consider applying it as a patch until the next upstream release.

Thanks. Please note that someone else at Canonical also submitted a MR
for an NMU on Salsa for this one. This is overkill. An NMU is not
welcome on an actively maintained package.

Martin-Éric

We believe that the bug you reported is fixed in the latest version of
dhcpcd, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1149297@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Martin-Éric Racine <martin-eric.racine@iki.fi> (supplier of updated dhcpcd package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Wed, 30 Sep 2026 07:48:01 +0300
Source: dhcpcd
Architecture: source
Version: 1:10.5.2-6
Distribution: unstable
Urgency: medium
Maintainer: Martin-Éric Racine <martin-eric.racine@iki.fi>
Changed-By: Martin-Éric Racine <martin-eric.racine@iki.fi>
Closes: 1149297
Changes:
 dhcpcd (1:10.5.2-6) unstable; urgency=medium
 .
   * [patches]
     + 0002: Fix stdout/stderr not closed when daemonising (Closes: #1149297).
Checksums-Sha1:
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 fd24ba8f2d2d51e80eb38ec6cc4c2452ec45c4cb 22352 dhcpcd_10.5.2-6.debian.tar.xz
 f0a1c2101e680d597f86c5bbc5a557b0cd55347c 5299 dhcpcd_10.5.2-6_source.buildinfo
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 291826556b6b580a6b5c3861949dfe86c0625364084af939d542abfde25ef558 22352 dhcpcd_10.5.2-6.debian.tar.xz
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 6764029a120136c312790aaca31ae985 22352 net optional dhcpcd_10.5.2-6.debian.tar.xz
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