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 <hreitz@redhat.com>
Message-Id: <20220303164814.284974-4-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We did not add documentation to the storage daemon's man page for fuse's
allow-other option when it was introduced, so do that now.
Fixes: 8fc54f9428 ("export/fuse: Add allow-other option")
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220131103124.20325-1-hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reported-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220107105420.395011-2-f4bug@amsat.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211118192744.64325-1-philmd@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Documents within a Sphinx manual are separate files and therefore can use
different conventions for headings. However, keeping some consistency is
useful so that included files are easy to get right.
This patch uses a standard heading format for book titles, so that it is
obvious when a file sits at the top level toctree of a book or man page.
The heading is irrelevant for man pages, but keep it consistent as well.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Implementing FUSE exports required no changes to the storage daemon, so
we forgot to document them there. Considering that both NBD and
vhost-user-blk exports are documented in its man page (and NBD exports
in its --help text), we should probably do the same for FUSE.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210217115844.62661-1-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
The 'name' option for NBD exports is optional. Add a note that the
default for the option is the node name (people could otherwise expect
that it's the empty string like for qemu-nbd).
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210305094856.18964-1-kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
World-writeable directories have security issues. Avoid showing them in
the documentation since someone might accidentally use them in
situations where they are insecure.
There tend to be 3 security problems:
1. Denial of service. An adversary may be able to create the file
beforehand, consume all space/inodes, etc to sabotage us.
2. Impersonation. An adversary may be able to create a listen socket and
accept incoming connections that were meant for us.
3. Unauthenticated client access. An adversary may be able to connect to
us if we did not set the uid/gid and permissions correctly.
These can be prevented or mitigated with private /tmp, carefully setting
the umask, etc but that requires special action and does not apply to
all situations. Just avoid using /tmp in examples.
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210301172728.135331-3-stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The QMP monitor, NBD server, and vhost-user-blk export all support file
descriptor passing. This is a useful technique because it allows the
parent process to spawn and wait for qemu-storage-daemon without busy
waiting, which may delay startup due to arbitrary sleep() calls.
This Python example is inspired by the test case written for libnbd by
Richard W.M. Jones <rjones@redhat.com>:
89113f484e
Thanks to Daniel P. Berrangé <berrange@redhat.com> for suggestions on
how to get this working. Now let's document it!
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210301172728.135331-2-stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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>
The preferred syntax is to use "foo=on|off", rather than a bare
"foo" or "nofoo".
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210216191027.595031-8-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Document the qemu-storage-daemon tool. Most of the command-line options
are identical to their QEMU counterparts. Perhaps Sphinx hxtool
integration could be extended to extract documentation for individual
command-line options so they can be shared. For now the
qemu-storage-daemon simply refers to the qemu(1) man page where the
command-line options are identical.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201209103802.350848-3-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
