lbu: add page (#14259)

Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>

pages/linux/lbu.md

@@ -0,0 +1,37 @@
+# lbu
+
+> Manage `apk` overlay files on a diskless Alpine Linux system.
+> Note: subcommands like `include` write to `/etc`, which is stored in RAM. You need to run `lbu commit` to save the changes.
+> More information: <https://wiki.alpinelinux.org/wiki/Alpine_local_backup>.
+
+- Commit changes to persistent storage (only files in `/etc` by default):
+
+`lbu {{ci|commit}}`
+
+- List files that would be saved using `commit`:
+
+`lbu {{st|status}}`
+
+- Display changes in tracked files that would be saved using `commit`:
+
+`lbu diff`
+
+- Include a specific file or directory in the `apk` overlay:
+
+`lbu {{add|inc|include}} {{path/to/file_or_directory}}`
+
+- Exclude a specific file or directory in `/etc` from the `apk` overlay:
+
+`lbu {{ex|exclude|delete}} {{path/to/file_or_directory}}`
+
+- Display the list of manually included/excluded files:
+
+`lbu {{inc|include|ex|exclude}} -l`
+
+- List backups (previously created overlays):
+
+`lbu {{lb|list-backup}}`
+
+- Revert to a backup overlay:
+
+`lbu revert {{overlay_filename.tar.gz}}`