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+ | 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. | ||
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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. | ||
− | + | == Filesystem layout == | |
− | < | + | OpenVZ uses two directories. Assuming our container is numbered 777, these directories are: |
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+ | * <code>VE_PRIVATE</code>: $VZDIR/private/777 | ||
+ | * <code>VE_ROOT</code>: $VZDIR/root/777 | ||
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+ | {{Note|<code>$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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+ | <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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+ | {{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>).}} | ||
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+ | == Manual mount example == | ||
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+ | On the HN we have a directory <code>/home</code> which we wish to make available (shared) to container 777. | ||
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+ | The correct command to issue on the HN is: | ||
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+ | mount --bind /home $VZDIR/root/777/home | ||
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+ | The container must be started (or at least mounted) and the destination directory must exist. The container will see this directory mounted like this: | ||
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+ | # df | ||
+ | Filesystem 1K-blocks Used Available Use% Mounted on | ||
+ | simfs 10485760 298728 10187032 3% / | ||
+ | ext3 117662052 104510764 7174408 94% /home | ||
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+ | During the container stop vzctl unmounts that bind mount, so you have to mount it again when you start the container for the next time. Luckily there is a way to automate it. | ||
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+ | == Make the mount persistent == | ||
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+ | Put a mount script in OpenVZ configuration directory (<code>/etc/vz/conf/</code>) with the name <code>''CTID''.mount</code> (where <code>''CTID''</code> is container ID, like 777). This script will be executed every time you run <code>vzctl mount</code> or <code>vzctl start</code> for a particular container. If you need to the same for all containers, use the global mount script named <code>vps.mount</code>. | ||
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+ | From any mount script you can use the following environment variables: | ||
+ | * <code>${VEID}</code> -- container ID (like <code>777</code>). | ||
+ | * <code>${VE_CONFFILE}</code> -- container configuration file (like <code>/etc/vz/conf/777.conf</code>) | ||
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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 === | |
− | + | 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>) | |
+ | #!/bin/bash | ||
+ | source /etc/vz/vz.conf | ||
+ | source ${VE_CONFFILE} | ||
+ | mount -n --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: | |
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− | . | ||
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− | + | mount --bind /home $VZDIR/root/777/home | |
− | + | mount --bind -oremount,ro $VZDIR/root/777/home | |
== See also == | == See also == | ||
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* [[NFS]] | * [[NFS]] | ||
* [[FUSE]] | * [[FUSE]] |