f1303afe22
The virtiofsd --help output documents the cache=auto default value but the man page does not. Fix this. Signed-off-by: Harry G. Coin <hgcoin@gmail.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20200916112250.760245-1-stefanha@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
124 lines
3.6 KiB
ReStructuredText
124 lines
3.6 KiB
ReStructuredText
QEMU virtio-fs shared file system daemon
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========================================
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Synopsis
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--------
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**virtiofsd** [*OPTIONS*]
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Description
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-----------
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Share a host directory tree with a guest through a virtio-fs device. This
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program is a vhost-user backend that implements the virtio-fs device. Each
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virtio-fs device instance requires its own virtiofsd process.
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This program is designed to work with QEMU's ``--device vhost-user-fs-pci``
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but should work with any virtual machine monitor (VMM) that supports
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vhost-user. See the Examples section below.
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This program must be run as the root user. Upon startup the program will
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switch into a new file system namespace with the shared directory tree as its
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root. This prevents "file system escapes" due to symlinks and other file
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system objects that might lead to files outside the shared directory. The
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program also sandboxes itself using seccomp(2) to prevent ptrace(2) and other
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vectors that could allow an attacker to compromise the system after gaining
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control of the virtiofsd process.
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Options
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-------
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.. program:: virtiofsd
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.. option:: -h, --help
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Print help.
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.. option:: -V, --version
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Print version.
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.. option:: -d
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Enable debug output.
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.. option:: --syslog
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Print log messages to syslog instead of stderr.
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.. option:: -o OPTION
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* debug -
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Enable debug output.
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* flock|no_flock -
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Enable/disable flock. The default is ``no_flock``.
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* modcaps=CAPLIST
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Modify the list of capabilities allowed; CAPLIST is a colon separated
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list of capabilities, each preceded by either + or -, e.g.
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''+sys_admin:-chown''.
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* log_level=LEVEL -
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Print only log messages matching LEVEL or more severe. LEVEL is one of
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``err``, ``warn``, ``info``, or ``debug``. The default is ``info``.
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* posix_lock|no_posix_lock -
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Enable/disable remote POSIX locks. The default is ``no_posix_lock``.
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* readdirplus|no_readdirplus -
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Enable/disable readdirplus. The default is ``readdirplus``.
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* source=PATH -
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Share host directory tree located at PATH. This option is required.
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* timeout=TIMEOUT -
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I/O timeout in seconds. The default depends on cache= option.
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* writeback|no_writeback -
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Enable/disable writeback cache. The cache allows the FUSE client to buffer
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and merge write requests. The default is ``no_writeback``.
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* xattr|no_xattr -
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Enable/disable extended attributes (xattr) on files and directories. The
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default is ``no_xattr``.
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.. option:: --socket-path=PATH
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Listen on vhost-user UNIX domain socket at PATH.
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.. option:: --fd=FDNUM
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Accept connections from vhost-user UNIX domain socket file descriptor FDNUM.
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The file descriptor must already be listening for connections.
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.. option:: --thread-pool-size=NUM
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Restrict the number of worker threads per request queue to NUM. The default
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is 64.
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.. option:: --cache=none|auto|always
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Select the desired trade-off between coherency and performance. ``none``
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forbids the FUSE client from caching to achieve best coherency at the cost of
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performance. ``auto`` acts similar to NFS with a 1 second metadata cache
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timeout. ``always`` sets a long cache lifetime at the expense of coherency.
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The default is ``auto``.
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Examples
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--------
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Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
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``/var/run/vm001-vhost-fs.sock``:
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::
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host# virtiofsd --socket-path=/var/run/vm001-vhost-fs.sock -o source=/var/lib/fs/vm001
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host# qemu-system-x86_64 \
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-chardev socket,id=char0,path=/var/run/vm001-vhost-fs.sock \
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-device vhost-user-fs-pci,chardev=char0,tag=myfs \
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-object memory-backend-memfd,id=mem,size=4G,share=on \
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-numa node,memdev=mem \
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...
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guest# mount -t virtiofs myfs /mnt
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