ZFS: Difference between revisions
imported>ThomasHertleif m Fix zfs trim option "enabled" to "enable" |
imported>Grahamc Show an example pool layout which keeps /nix out of the hierarchy of /, and create a list of explicitly recommended dataset properties. |
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== How to install NixOS on a ZFS root filesystem == | == How to install NixOS on a ZFS root filesystem == | ||
=== Pool Layout Considerations === | |||
it is important to keep <code>/nix</code> and the rest of the filesystem in | |||
different sections of the dataset hierarchy, like this: | |||
<syntaxhighlight lang="console"> | |||
rpool/ | |||
local/ | |||
nix mounted to /nix | |||
safe/ | |||
root mounted to / | |||
home mounted to /home | |||
... | |||
</syntaxhighlight> | |||
the name of `local` and `safe` can change, but them being peers | |||
is important. | |||
ZFS can take consistent and atomic snapshots recursively down a | |||
dataset's hierarchy. Since Nix is good at being Nix, we almost | |||
never want to take snapshots of <code>/nix</code> as well. Regular system | |||
backups certainly shouldn't. | |||
=== Dataset Properties === | |||
The following is a list of recommended dataset properties which have no drawbacks under regular uses: | |||
* <code>compression=lz4</code> | |||
* <code>xattr=sa</code> for Journald | |||
* <code>acltype=posixacl</code> also for Journald | |||
The following is a list of dataset properties which are often useful, but do have drawbacks: | |||
* <code>atime=off</code> disables if a file's access time is updated when the file is read. This can result in significant performance gains, but might confuse some software like mailers. | |||
==== Journald ==== | |||
Journald requires some properties for <code>journalctl</code> to work for non-root users. The dataset containing <code>/var/log/journal</code> (probably the <code>/</code> dataset for simple configurations) should be created with <code>xattr=sa</code> and <code>acltype=posixacl</code>. | |||
For example: | |||
<syntaxhighlight lang="console"> | |||
$ zpool create -O xattr=sa -O acltype=posixacl rpool ... | |||
</syntaxhighlight> | |||
or: | |||
<syntaxhighlight lang="console"> | |||
$ zfs create -o xattr=sa -o acltype=posixacl rpool/root | |||
</syntaxhighlight> | |||
If you have already created the dataset, these properties can be set later: | |||
<syntaxhighlight lang="console"> | |||
$ zfs set xattr=sa acltype=posixacl rpool/root | |||
</syntaxhighlight> | |||
=== Single-disk === | === Single-disk === | ||