28 lines
700 B
Markdown
28 lines
700 B
Markdown
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# Overlayfs {#sec-overlayfs}
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NixOS offers a convenient abstraction to create both read-only as well writable
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overlays.
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```nix
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fileSystems = {
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"/writable-overlay" = {
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overlay = {
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lowerdir = [ writableOverlayLowerdir ];
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upperdir = "/.rw-writable-overlay/upper";
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workdir = "/.rw-writable-overlay/work";
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};
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# Mount the writable overlay in the initrd.
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neededForBoot = true;
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};
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"/readonly-overlay".overlay.lowerdir = [
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writableOverlayLowerdir
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writableOverlayLowerdir2
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];
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};
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```
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If `upperdir` and `workdir` are not null, they will be created before the
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overlay is mounted.
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To mount an overlay as read-only, you need to provide at least two `lowerdir`s.
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