Difference between revisions of "Bind mounts"

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(fixed to use simfs, use -n, don't do umount script)
m (Better wording to clarify that the additional script is not a replacement for the one above, but rather needs to be run first.)
 
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Bind mounts can be used to make directories on the hardware node visible to the container.
 
Bind mounts can be used to make directories on the hardware node visible to the container.
  
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== Filesystem layout ==
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This is how you can make host system's <code>/mnt/disk</code> directory available to a container 777:
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OpenVZ uses two directories. Assuming our container is numbered 777, these directories are:
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<source lang="bash">
 +
CTID=777
  
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* <code>VE_PRIVATE</code>: $VZDIR/private/777
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echo '#!/bin/bash
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* <code>VE_ROOT</code>: $VZDIR/root/777
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. /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
  
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{{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.}}
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chmod +x /etc/vz/conf/${CTID}.mount
 +
</source>
  
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<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>
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If you want read-only mount, add <code>-r</code> option to mount command.
  
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{{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>).}}
+
{{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.)}}
  
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== Mounting ==
 
  
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Put a 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>.
+
'''Instruction above will not work on OpenVZ 7 until you run the script below to enable Bind mounts:'''
  
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From any mount script you can use the following environment variables:
 
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* <code>${VEID}</code> -- container ID (like <code>777</code>).
 
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* <code>${VE_CONFFILE}</code> -- container configuration file (like <code>/etc/vz/conf/777.conf</code>)
 
−
 
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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>.
 
−
 
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=== Mount script example ===
 
−
 
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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 lang="bash">
 
<source lang="bash">
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CTID=777
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cat <<'EOF' > /etc/vz/conf/vps.mount
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cat << EOF > /etc/vz/conf/${CTID}.mount
 
 
#!/bin/bash
 
#!/bin/bash
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source /etc/vz/vz.conf
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. ${VE_CONFFILE}
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source ${VE_CONFFILE}
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VE_MOUNT=$(echo ${VE_CONFFILE} | sed 's/\.conf$/.mount/')
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mount -n -t simfs /mnt/disk ${VE_ROOT}/mnt/disk -o /mnt/disk
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[ -x ${VE_MOUNT} ] && . ${VE_MOUNT}
 +
exit 0
 
EOF
 
EOF
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chmod +x /etc/vz/conf/${CTID}.mount
+
 
 +
chmod +x /etc/vz/conf/vps.mount
 +
</source>
  
 
== See also ==
 
== See also ==
 +
* {{Man|vzctl|8}} (ACTION SCRIPTS section)
 
* [[NFS]]
 
* [[NFS]]
 
* [[FUSE]]
 
* [[FUSE]]

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.

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

See also[edit]

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