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| − | + | == Mounting filesystems within a VE == | |
| − | + | To mount filesystems inside a VE, you have several choices: | |
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| − | + | * NFS (the VE will be an NFS Client) - see [[NFS]] | |
| + | * FUSE - see [[FUSE]] | ||
| + | * Bind mount from Hardware Node | ||
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| + | === Bind mount from Hardware Node === | ||
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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 bind' for more information. | ||
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| + | Bind mounts can be used to make directories on the hardware node visible to the VE. | ||
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| + | OpenVZ uses two directories. Assuming our VE is numbered 777, these directories are: | ||
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| + | $VZROOT/private/777 | ||
| + | $VZROOT/root/777 | ||
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| + | {{Note|<code>$VZROOT</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>/vz</code>.}} | ||
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| + | The /vz/private directory contains root directory contents. This directory or subdirectory may be symlinked onto a different filesystem, for example: | ||
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| + | /vz/private -> /mnt/openvz | ||
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| + | Putting VE root directories onto a separate filesystem (not the hardware node root filesystem) is good storage management practice. It protects the Hardware Node root filesystem from being filled up by a VE; this could cause problems on the Hardware Node. | ||
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| + | === Requirement === | ||
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| + | '''On the HN we have a directory <code>/home</code> which we wish to make available (shared) to all VEs.''' | ||
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| + | You would think that you could bind mount this directory, as in: <code>mount --bind /home $VZROOT/private/777/home</code> but this does not work — the contents of <code>/home</code> cannot be seen within the VE. | ||
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| + | This is where the second directory listed above (<code>$VZROOT/root/777</code>) is used. If a VE is not started, this directory is empty. But after starting a VE, this directory contains what the VE sees as its mounted file systems. | ||
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| + | The correct command to issue on the HN is: | ||
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| + | mount --bind /home $VZROOT/root/777/home | ||
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| + | The VE must be started and the destination directory must exist. The VE 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% / | ||
| + | tmpfs 484712 0 484712 0% /lib/init/rw | ||
| + | tmpfs 484712 0 484712 0% /dev/shm | ||
| + | ext3 117662052 104510764 7174408 94% /home | ||
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| + | [[Category:HOWTO]] | ||
