43 lines
1.8 KiB
Markdown
43 lines
1.8 KiB
Markdown
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# File Systems {#ch-file-systems}
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You can define file systems using the `fileSystems` configuration
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option. For instance, the following definition causes NixOS to mount the
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Ext4 file system on device `/dev/disk/by-label/data` onto the mount
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point `/data`:
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```nix
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fileSystems."/data" =
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{ device = "/dev/disk/by-label/data";
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fsType = "ext4";
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};
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```
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This will create an entry in `/etc/fstab`, which will generate a
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corresponding [systemd.mount](https://www.freedesktop.org/software/systemd/man/systemd.mount.html)
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unit via [systemd-fstab-generator](https://www.freedesktop.org/software/systemd/man/systemd-fstab-generator.html).
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The filesystem will be mounted automatically unless `"noauto"` is
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present in [options](#opt-fileSystems._name_.options). `"noauto"`
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filesystems can be mounted explicitly using `systemctl` e.g.
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`systemctl start data.mount`. Mount points are created automatically if they don't
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already exist. For `device`, it's best to use the topology-independent
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device aliases in `/dev/disk/by-label` and `/dev/disk/by-uuid`, as these
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don't change if the topology changes (e.g. if a disk is moved to another
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IDE controller).
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You can usually omit the file system type (`fsType`), since `mount` can
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usually detect the type and load the necessary kernel module
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automatically. However, if the file system is needed at early boot (in
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the initial ramdisk) and is not `ext2`, `ext3` or `ext4`, then it's best
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to specify `fsType` to ensure that the kernel module is available.
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::: {.note}
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System startup will fail if any of the filesystems fails to mount,
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dropping you to the emergency shell. You can make a mount asynchronous
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and non-critical by adding `options = [ "nofail" ];`.
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:::
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```{=docbook}
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<xi:include href="luks-file-systems.section.xml" />
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<xi:include href="sshfs-file-systems.section.xml" />
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```
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