From 2525edd85fec53e23fda98974a15e3b3c8957596 Mon Sep 17 00:00:00 2001 From: Hanna Reitz Date: Thu, 3 Mar 2022 17:48:13 +0100 Subject: qsd: Add --daemonize To implement this, we reuse the existing daemonizing functions from the system emulator, which mainly do the following: - Fork off a child process, and set up a pipe between parent and child - The parent process waits until the child sends a status byte over the pipe (0 means that the child was set up successfully; anything else (including errors or EOF) means that the child was not set up successfully), and then exits with an appropriate exit status - The child process enters a new session (forking off again), changes the umask, and will ignore terminal signals from then on - Once set-up is complete, the child will chdir to /, redirect all standard I/O streams to /dev/null, and tell the parent that set-up has been completed successfully In contrast to qemu-nbd's --fork implementation, during the set up phase, error messages are not piped through the parent process. qemu-nbd mainly does this to detect errors, though (while os_daemonize() has the child explicitly signal success after set up); because we do not redirect stderr after forking, error messages continue to appear on whatever the parent's stderr was (until set up is complete). Signed-off-by: Hanna Reitz Message-Id: <20220303164814.284974-4-hreitz@redhat.com> Signed-off-by: Kevin Wolf --- docs/tools/qemu-storage-daemon.rst | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'docs/tools/qemu-storage-daemon.rst') diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst index 878e6a5c5c..8b97592663 100644 --- a/docs/tools/qemu-storage-daemon.rst +++ b/docs/tools/qemu-storage-daemon.rst @@ -154,6 +154,13 @@ Standard options: created but before accepting connections. The daemon has started successfully when the pid file is written and clients may begin connecting. +.. option:: --daemonize + + Daemonize the process. The parent process will exit once startup is complete + (i.e., after the pid file has been or would have been written) or failure + occurs. Its exit code reflects whether the child has started up successfully + or failed to do so. + Examples -------- Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute -- cgit v1.2.3