Alpine local backup
When Alpine Linux boots in diskless mode, it initially only loads a few required packages from the boot device.
However, local adjustments to what-gets-loaded-into-RAM are possible, e.g. by installing a package or adjusting the configuration files in /etc. The modifications can be saved to an overlay file (.apkovl) that can be automatically loaded when booting, to restore the saved state.
The .apkovl file that contains the custom configuration can be saved to writable storage with Alpine's local backup utility lbu. By configuring a local package cache the additional packages the configuration depends on, can also be kept available on local, writable storage.
lbu to save the system state. With a system disk, all modifications are
written directly to disk. Nevertheless, lbu can be useful for some maintenance tasks.
By default, an lbu commit only stores modifications below /etc, with the exception of the /etc/init.d/ directory.
If a user was created during the setup-alpine script, that user's home directory is also added to the paths that lbu will backup up.
However, lbu include enables modifying that set of included files, and can be used to specify additional files or folders.
Saving and loading ISO image customizations
Committing changes
The lbu tool has several subcommands to manage the .apkovl:
- lbu
- lbu commit (Same as 'lbu ci')
- lbu package (Same as 'lbu pkg')
- lbu status (Same as 'lbu st')
- lbu list (Same as 'lbu ls')
- lbu diff
- lbu include (Same as 'lbu inc' or 'lbu add')
- lbu exclude (Same as 'lbu ex' or 'lbu delete')
- lbu list-backup (Same as 'lbu lb')
- lbu revert
In the examples below, you will find some characters with special meaning:
- | = or ('lbu commit|ci' means that you can type ether 'lbu commit' or 'lbu ci')
- [ ] = optional (In 'lbu commit|ci [-nv]' you can skip the '-n', '-v' or '-nv' part if you don't want it)
Basic "commit" command
When you "commit" or save changes you've made to your system, lbu will generate a file named something like myboxname.apkovl.tar.gz ('myboxname' will be the same as the hostname).
The file (which contains your modifications) is called your "apkovl".
You will need to save your apkovl on suitable media (floppy, usb, cf, etc.).
usage: lbu commit|ci [-nv] [<media>] Options: -d Remove old apk overlay files. -e Protect configuration with a password. -n Don't commit, just show what would have been committed. -p <password> Give encryption password on the command-line -v Verbose mode. The following values for <media> are supported: floppy usb If <media> is not specified, the environment variable LBU_MEDIA will be used. Password protection will use aes-256-cbc encryption. Other ciphers can be used by setting the DEFAULT_CIPHER or ENCRYPTION environment variables. For possible ciphers, try: openssl -v The password used to encrypt the file, can be specified with the -p option or by using the PASSWORD environment variable. The environment variable can also be set in /etc/lbu/lbu.conf
Creating an .apkovl "package" elsewhere than on the configured media
To "commit" changes, but override the destination of the generated apkovl file, use lbu package instead of lbu commit:
usage: lbu package|pkg -v [<dirname>|<filename>] Options: -v Verbose mode. If <dirname> is a directory, a package named <hostname>.apkovl.tar.gz will be created in the specified directory. If <filename> is specified, and is not a directory, a package with the specified name will be created. If neither <dirname> nor <filename> is specified, a package named <hostname>.apkovl.tar.gz will be created in the current working directory.
Creating and saving an apkovl from a remote host
To create an apkovl from a client on a remote server, it's possible to use lbu package via SSH with - as the apkovl name:
On the server:
ssh root@client "lbu package -" >client.apkovl.tar.gz
Checking what will be added to your apkovl
lbu status lists what will be saved the next time you run lbu commit. Its default output is incremental, that is, it shows
only the files that have changed since the last commit.
This can be overridden with the -a flag:
usage: lbu status|st [-av] Options: -a Compare all files, not just since last commit. -v show include and exclude lists.
Another option is lbu list. This works like lbu status -a but the format of the output is a bit different. (It's strictly equivalent to lbu package -v /dev/null).
usage: lbu list|ls
A third option is lbu diff. This shows the same incremental changes that lbu status (without -a) does, but in a different format.
usage: lbu diff
Include special files/folders to the apkovl
Assume you have some files you want to save permanently, but they are not located in /etc.
e.g. /root/.ssh/authorized_keys (used by sshd to authenticate ssh-users). Such files/folders can be added to lbu's include list with the following command:
usage: lbu include|inc|add [-rv] <file> ...
lbu include|inc|add [-v] -l
Options:
-l List contents of include list.
-r Remove specified file(s) from include list.
-v Verbose mode.
lbu include only modifies lbu's configuration.
You will need to run lbu commit to actually create/modify your apkovl.
Exclude specific files/folders from the apkovl
Assume you have some files located in /etc or one of its subfolders you do not want to save.
It could be a log file or status file that for some reason isn't in /var/log/ but in a location that would otherwise be tracked by lbu.
Such files/folders can be added to lbu's exclude list by manually editing the file or using the following command:
usage: lbu exclude|ex|delete [-rv] <file> ...
lbu exclude|ex|delete [-v] -l
Options:
-l List contents of exclude list.
-r Remove specified file(s) from exclude list.
-v Verbose mode.
lbu exclude also only modifies lbu's configuration. You will need to run
lbu commit to actually create/modify your apkovl.
Execute a script as part of a backup
Sometimes it's necessary to run a script before or after a backup. Scripts in two optional directories enable that:
/etc/lbu/pre-package.d /etc/lbu/post-package.d
Files in those directories are run using run-script rules (meaning they must have the executable bit set, they are run in alphabetical order, and cannot contain an extension. e.g. runme works, but runme.sh does not. Also the shebang line on the first line should be indicated, e.g. #!/bin/sh .)
The scripts in pre-package.d are run before apkovl is created. Scripts in post-package.d are run after apkovl is created.
Example
Rather than adding the raw database directories to /etc/lbu/include, you can do a "database dump". e.g. postgresql:
- Create /etc/lbu/pre-package.d/sqldump with the following contents:
pg_dumpall -U postgres | gzip -c >/root/pgdatabases.gz
- Mark the file executable:
chmod +x /etc/lbu/pre-package.d/sqldump - Create /etc/lbu/post-package.d/sqldumpdelete with the following contents:
rm -f /root/pgdatabases.gz
- Mark the file executable:
chmod +x /etc/lbu/post-package.d/sqldumpdelete - Finally, add the database dump file to the list of files to back up:
lbu include root/pgdatabases.gz
Now when you do a lbu commit, the sql databases are dumped and gzipped to /root/pgdatabases.gz.
The temporary file is deleted at the end of the lbu commit.
On a catastrophic restore, the databases are not automatically restored (that's not lbu's job), but you will find a complete database dump in the /root directory, where it can be restored manually.
P.s. These scripts are also launched when starting the commands: diff, list-backup, package, revert, status.
Multiple backup versions
Lbu can now keep multiple backups so you can revert back to older configurations. Set BACKUP_LIMIT in /etc/lbu/lbu.conf to the number of backups you want to keep.
If you've set BACKUP_LIMIT, then the previously active .apkovl will be renamed before creating the new file.
You can list the currently available backups with:
lbu list-backup [<media>]
and you can revert to an older one with:
lbu revert <filename> [<media>]
NOTE: Nothing is changed on your running system when "reverting", it only affects which apkovl is considered active at the next boot.