From 03d2b412aaf2078425f8472f31c8a9c2340969eb Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Tue, 2 Mar 2021 14:27:46 +0000
Subject: qemu-storage-daemon: add --pidfile option

Daemons often have a --pidfile option where the pid is written to a file
so that scripts can stop the daemon by sending a signal.

The pid file also acts as a lock to prevent multiple instances of the
daemon from launching for a given pid file.

QEMU, qemu-nbd, qemu-ga, virtiofsd, and qemu-pr-helper all support the
--pidfile option. Add it to qemu-storage-daemon too.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210302142746.170535-1-stefanha@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 docs/tools/qemu-storage-daemon.rst | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'docs/tools')

diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst
index c05b3d3..6ce85f2 100644
--- a/docs/tools/qemu-storage-daemon.rst
+++ b/docs/tools/qemu-storage-daemon.rst
@@ -118,6 +118,20 @@ Standard options:
   List object properties with ``<type>,help``. See the :manpage:`qemu(1)`
   manual page for a description of the object properties.
 
+.. option:: --pidfile PATH
+
+  is the path to a file where the daemon writes its pid. This allows scripts to
+  stop the daemon by sending a signal::
+
+    $ kill -SIGTERM $(<path/to/qsd.pid)
+
+  A file lock is applied to the file so only one instance of the daemon can run
+  with a given pid file path. The daemon unlinks its pid file when terminating.
+
+  The pid file is written after chardevs, exports, and NBD servers have been
+  created but before accepting connections. The daemon has started successfully
+  when the pid file is written and clients may begin connecting.
+
 Examples
 --------
 Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute
-- 
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