undaemonize

This is a tiny helper utility to force programs which insist on daemonizing themselves to run in the foreground.

It's like djb's fghack, except it's not a hack, because it makes use of the PR_SET_CHILD_SUBREAPER flag added to prctl(2) in version 3.4 of the Linux kernel. To quote the documentation:

When a process is marked as a child subreaper, all of the children that it
creates, and their descendants, will be marked as having a subreaper.  In
effect, a subreaper fulfills the role of init(1) for its descendant
processes.  Upon termination of a process that is orphaned (i.e., its
immediate parent has already terminated) and marked as having a subreaper,
the nearest still living ancestor subreaper will receive a SIGCHLD signal
and will be able to wait(2) on the process to discover its termination
status.

Usage

undaemonize foobard -f /etc/foobard.conf

Installation

make
sudo install -o root -g root -m 755 undaemonize /usr/local/bin

Caveats

undaemonize does not (currently) forward signals to its child processes. If you kill undaemonize, the daemon will not be killed.

License

undaemonize is released under the MIT license. See LICENSE.