Difference between revisions of "Bind mounts"

Latest revision as of 13:17, 20 November 2017

Bind mounts can be used to make directories on the hardware node visible to the container.

This is how you can make host system's /mnt/disk directory available to a container 777:

CTID=777

echo '#!/bin/bash
. /etc/vz/vz.conf
. ${VE_CONFFILE}
SRC=/mnt/disk
DST=/mnt/disk
if [ ! -e ${VE_ROOT}${DST} ]; then mkdir -p ${VE_ROOT}${DST}; fi
mount -n -t simfs ${SRC} ${VE_ROOT}${DST} -o ${SRC}
' > /etc/vz/conf/${CTID}.mount

chmod +x /etc/vz/conf/${CTID}.mount

If you want read-only mount, add -r option to mount command.

Note: When specifying destination directory, always use /vz/root/ or ${VE_ROOT} env. variable (avoid using /vz/private)

Note: When binding directories from one container to another, make sure you have proper boot order (See BOOTORDER param.)

Instruction above will not work on OpenVZ 7 until you run the script below to enable Bind mounts:

cat <<'EOF' > /etc/vz/conf/vps.mount
#!/bin/bash
. ${VE_CONFFILE}
VE_MOUNT=$(echo ${VE_CONFFILE} | sed 's/\.conf$/.mount/')
[ -x ${VE_MOUNT} ] && . ${VE_MOUNT}
exit 0
EOF

chmod +x /etc/vz/conf/vps.mount

@@ Line 1: / Line 1: @@
-Recent Linux kernels support an operation called 'bind mounting' which makes part of a mounted filesystem visible at some other mount point. See 'man mount' for more information.
 Bind mounts can be used to make directories on the hardware node visible to the container.
-== Filesystem layout ==
+This is how you can make host system's <code>/mnt/disk</code> directory available to a container 777:
-OpenVZ uses two directories. Assuming our container is numbered 777, these directories are:
+<source lang="bash">
+CTID=777
-* <code>VE_PRIVATE</code>: $VZDIR/private/777
-* <code>VE_ROOT</code>: $VZDIR/root/777
-{{Note|<code>$VZDIR</code> is usually <code>/vz</code>, on Debian systems however this is <code>/var/lib/vz</code>. In this document this is further referred to as <code>$VZDIR</code> -- substitute it with what you have.}}
-<code>VE_PRIVATE</code> is a place for all the container files. <code>VE_ROOT</code> is the mount point to which <code>VE_PRIVATE</code> is mounted during container start (or when you run <code>vzctl mount</code>
-{{Warning|If you want to do a bind mount for container, you need to '''use <code>VE_ROOT</code>''' (not <code>VE_PRIVATE</code>!) and '''make sure that container is mounted''' (this can be checked using <code>vzctl status</code>).}}
-== Manual mount example ==
-On the HN we have a directory <code>/home</code> which we wish to make available (shared) to container 777.
-The correct command to issue on the HN is:
-  mount --bind /home $VZDIR/root/777/home
-The container must be started (or at least mounted) and the destination directory must exist. The container will see this directory mounted like this:
- # df
+echo '#!/bin/bash
- Filesystem           1K-blocks      Used Available Use% Mounted on
+. /etc/vz/vz.conf
- simfs                 10485760    298728  10187032   3% /
+. ${VE_CONFFILE}
- ext3                 117662052 104510764   7174408  94% /home
+SRC=/mnt/disk
+DST=/mnt/disk
+if [ ! -e ${VE_ROOT}${DST} ]; then mkdir -p ${VE_ROOT}${DST}; fi
+mount -n -t simfs ${SRC} ${VE_ROOT}${DST} -o ${SRC}
+' > /etc/vz/conf/${CTID}.mount
-During the container stop vzctl unmounts that bind mount, so you have to mount it again when you start the container for the next time. Luckily there is a way to automate it.
+chmod +x /etc/vz/conf/${CTID}.mount
+</source>
-== Make the mount persistent ==
+If you want read-only mount, add <code>-r</code> option to mount command.
-Put a mount script in OpenVZ configuration directory (<code>/etc/vz/conf/</code>) with the name <code>''CTID''.mount</code> (where <code>''CTID''</code> is container ID, like 777). This script will be executed every time you run <code>vzctl mount</code> or <code>vzctl start</code> for a particular container. If you need to the same for all containers, use the global mount script named <code>vps.mount</code>.
+{{Note|When specifying destination directory, always use /vz/root/ or ${VE_ROOT} env. variable <nowiki>(avoid using /vz/private)</nowiki>}}
+{{Note|When binding directories from one container to another, make sure you have proper boot order (See [[Man/vzctl.8|BOOTORDER]] param.)}}
-From any mount script you can use the following environment variables:
-* <code>${VEID}</code> -- container ID (like <code>777</code>).
-* <code>${VE_CONFFILE}</code> -- container configuration file (like <code>/etc/vz/conf/777.conf</code>)
-Now, in order to get the value of <code>VE_ROOT</code> you need to source both the global OpenVZ configuration file, and then the container configuration file, in that particular order. This is the same way vzctl uses to determine <code>VE_ROOT</code>.
+'''Instruction above will not work on OpenVZ 7 until you run the script below to enable Bind mounts:'''
+<source lang="bash">
+cat <<'EOF' > /etc/vz/conf/vps.mount
+#!/bin/bash
+. ${VE_CONFFILE}
+VE_MOUNT=$(echo ${VE_CONFFILE} | sed 's/\.conf$/.mount/')
+[ -x ${VE_MOUNT} ] && . ${VE_MOUNT}
+exit 0
+EOF
-=== Mount script example ===
+chmod +x /etc/vz/conf/vps.mount
-Here is an example of such a mount script (it can either be <code>/etc/vz/conf/vps.mount</code> or <code>/etc/vz/conf/''CTID''.mount</code>)
+</source>
- #!/bin/bash
- source /etc/vz/vz.conf
- source ${VE_CONFFILE}
- mount --bind /mnt/disk ${VE_ROOT}/mnt/disk
-=== Unmount script example ===
-For unmounting a filesystem, <code>/etc/vz/conf/vps.umount</code> or <code>/etc/vz/conf/''CTID''.umount</code> script can be used in the same way:
- #!/bin/bash
- source /etc/vz/vz.conf
- source ${VE_CONFFILE}
- umount ${VE_ROOT}/mnt/disk
-{{Note|<code>''CTID''.umount</code> script is not strictly required, since vzctl tries to unmount everything on CT stop. But you'd better have it anyway.}}
-== Read-only bind mounts ==
-Since Linux kernel 2.6.26, bind mounts can be made read-only. The trick is to first mount as usual, and then remount it read-only:
- mount --bind /home $VZDIR/root/777/home
- mount --bind -oremount,ro $VZDIR/root/777/home
 == See also ==
+* {{Man|vzctl|8}} (ACTION SCRIPTS section)
 * [[NFS]]
 * [[FUSE]]
 * [[Mounting filesystems]]
+[[Category:HOWTO]]

OpenVZ Virtuozzo Containers Wiki ^β

Difference between revisions of "Bind mounts"

Latest revision as of 13:17, 20 November 2017

See alsoEdit

OpenVZ Virtuozzo Containers Wiki β

Difference between revisions of "Bind mounts"

Latest revision as of 13:17, 20 November 2017

See alsoEdit

OpenVZ Virtuozzo Containers Wiki ^β