VIRTIOFSD(1) QEMU VIRTIOFSD(1)
NAME
virtiofsd - QEMU virtio-fs shared file system daemon
SYNOPSIS
virtiofsd [OPTIONS]
DESCRIPTION
Share a host directory tree with a guest through a virtio-fs device.
This program is a vhost-user backend that implements the virtio-fs de-
vice. Each virtio-fs device instance requires its own virtiofsd
process.
This program is designed to work with QEMU's --device vhost-user-fs-pci
but should work with any virtual machine monitor (VMM) that supports
vhost-user. See the Examples section below.
This program must be run as the root user. Upon startup the program
will switch into a new file system namespace with the shared directory
tree as its root. This prevents "file system escapes" due to symlinks
and other file system objects that might lead to files outside the
shared directory. The program also sandboxes itself using seccomp(2)
to prevent ptrace(2) and other vectors that could allow an attacker to
compromise the system after gaining control of the virtiofsd process.
OPTIONS
-h, --help
Print help.
-V, --version
Print version.
-d Enable debug output.
--syslog
Print log messages to syslog instead of stderr.
-o OPTION
o debug - Enable debug output.
o flock|no_flock - Enable/disable flock. The default is
no_flock.
o log_level=LEVEL - Print only log messages matching LEVEL or
more severe. LEVEL is one of err, warn, info, or debug. The
default is info.
o norace - Disable racy fallback. The default is false.
o posix_lock|no_posix_lock - Enable/disable remote POSIX locks.
The default is posix_lock.
o readdirplus|no_readdirplus - Enable/disable readdirplus. The
default is readdirplus.
o source=PATH - Share host directory tree located at PATH. This
option is required.
o timeout=TIMEOUT - I/O timeout in seconds. The default depends
on cache= option.
o writeback|no_writeback - Enable/disable writeback cache. The
cache alows the FUSE client to buffer and merge write re-
quests. The default is no_writeback.
o xattr|no_xattr - Enable/disable extended attributes (xattr) on
files and directories. The default is no_xattr.
--socket-path=PATH
Listen on vhost-user UNIX domain socket at PATH.
--fd=FDNUM
Accept connections from vhost-user UNIX domain socket file de-
scriptor FDNUM. The file descriptor must already be listening
for connections.
--thread-pool-size=NUM
Restrict the number of worker threads per request queue to NUM.
The default is 64.
--cache=none|auto|always
Select the desired trade-off between coherency and performance.
none forbids the FUSE client from caching to achieve best co-
herency at the cost of performance. auto acts similar to NFS
with a 1 second metadata cache timeout. always sets a long
cache lifetime at the expense of coherency.
EXAMPLES
Export /var/lib/fs/vm001/ on vhost-user UNIX domain socket
/var/run/vm001-vhost-fs.sock:
host# virtiofsd --socket-path=/var/run/vm001-vhost-fs.sock -o source=/var/lib/fs/vm001
host# qemu-system-x86_64 \
-chardev socket,id=char0,path=/var/run/vm001-vhost-fs.sock \
-device vhost-user-fs-pci,chardev=char0,tag=myfs \
-object memory-backend-memfd,id=mem,size=4G,share=on \
-numa node,memdev=mem \
...
guest# mount -t virtiofs myfs /mnt
AUTHOR
Stefan Hajnoczi <stefanha@redhat.com>, Masayoshi Mizuma
<m.mizuma@jp.fujitsu.com>
COPYRIGHT
2020, The QEMU Project Developers
5.0.0 Jul 22, 2020 VIRTIOFSD(1)