nbdkit-client - Man Page

how to mount NBD filesystems on a client machine

Description

For NBD exports that contain filesystems there are several approaches to mounting them on a client machine.

To ensure the nbd kernel module is loaded you may need to do:

 # echo nbd > /etc/modules-load.d/nbd.conf

This will not take effect until you reboot, so also do:

 # modprobe nbd

Easy mounting at boot time

For simple setups the following method is the easiest way to get an NBD filesystem to mount at boot.  Create or edit /etc/rc.local or /etc/rc.d/rc.local:

 #!/bin/sh -
 nm-online
 modprobe nbd
 nbd-client server /dev/nbd0
 mount /dev/nbd0 /mnt

Mounting using systemd mount points

You can use systemd mount points to mount NBD filesystems at boot and/or on demand.

Set up an nbdtab(5) mapping.  If /etc/nbdtab doesn't exist, then create it first.  Add this line:

 nbd0 server / bs=512,persist

As a workaround for https://github.com/NetworkBlockDevice/nbd/issues/91 you must currently modify the nbd@.service file:

 # cp /usr/lib/systemd/system/nbd@.service /etc/systemd/system/
 # vi /etc/systemd/system/nbd@.service

and edit or create these settings in the [Service] section:

 [Service]
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=/usr/sbin/nbd-client %i
 ExecStop=/usr/sbin/nbd-client -d /dev/%i

Finally create a systemd mount file called /etc/systemd/system/mnt.mount:

 [Unit]
 Requires=nbd@nbd0.service
 [Mount]
 What=/dev/nbd0
 Where=/mnt
 Type=ext4

You can either reboot now or do:

 # systemctl start mnt.mount

Other systemd services which need this mount point can depend on this mount unit.

See Also

nbdkit(1), nbdkit-loop(1), nbdkit-service(1), nbd-client(8), nbdtab(5), systemd(1), systemd.mount(5).

Authors

Richard W.M. Jones

License

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Referenced By

nbdkit(1), nbdkit-loop(1), nbdkit-release-notes-1.22(1), nbdkit-service(1), nbdkit-tmpdisk-plugin(1).

2021-07-23 nbdkit-1.27.3