Alpine local backup

2021-10-16T14:12:06Z

Rylan: /* Saving and loading ISO image customizations */

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 [[Alpine_package_management|installing a package]] or adjusting the configuration files in {{path|/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 <code>lbu</code>. By configuring a [[Alpine_Linux_package_management#Local_Cache|local package cache]] the additional packages the configuration depends on, can also be kept available on local, writable storage.

{{Note|If you installed Alpine in "sys" disk mode, you don't need to use <code>lbu</code> to save the system state. With a system disk, all modifications are
written directly to disk. Nevertheless, <code>lbu</code> can be useful for some maintenance tasks.}}

__TOC__

{{Warning|
'''By default, an <code>lbu commit</code> only stores modifications below {{Path|/etc}}''', with the exception of the {{Path|/etc/init.d/}} directory.

However, [[#Include_special_files.2Ffolders_to_the_apkovl|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 ==

Besides supporting a boot parameter to load customizations from a web server, Alpine's "diskless mode" ISO images try to load an .apkovl volume from system partitions. It is therefore possible to save customized running states to a .apkovl file on a writable partition, and have these automatically loaded when booting the ISO image.

{{Note|When the machine reboots, the remote repositories will not be available until after networking has started. That means packages newer than on your local boot media would not be available after a reboot, unless they were made to persistent, by having a [[#Local Cache|local package cache]] available on a local, writable, storage device.}}

The local package cache, which enables additional and updated packages to automatically be copied into RAM during boot, may be stored on the same partition as the .apkovl file.

To use partitions on '''internal disks''', however, you need to prepare a specific /etc/fstab entry manually, and save the configuration, as follows (setup-alpine does not list them for saving configs or package cache):

1. Boot the diskless system from ISO (as shown at [[Installation]]) 
2. If necessary, create and format a partition as in [[Setting_up_disks_manually#For_.22diskless.22_and_.22data.22_disk_mode_installs_2]]. For the examples we will use /dev/sdXY 
* Bug: [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/issues/5 Initramfs-init does not respect apkovl device fstab entry], so the partition can not be mounted to /boot. The workaround given there does not seem to work (e.g. <code>mkdir -p /boot/ovl_dev/cache ; touch /boot/ovl_dev/cache/.boot_repository</code>) 
=> Alternative: Configure the /etc/fstab to mount the writable partition to /media/sdXY instead of /boot (i.e. conforming to the hot/cold-plug mountpoints): 
3. <code>mkdir /media/sdXY</code> 
4. <code>echo "/dev/sdXY /media/sdXY ext4 noatime,ro 0 0" >> /etc/fstab</code> (Mounting read-only is possible, because the tools temporarily remount it writable for their operation.) 
5. Use <code>mount -a</code> to load the partitions listed in /etc/fstab. Look at the output of <code>mount</code> to verify that the /etc/fstab changes have been applied correctly. 
6. If setup-alpine has not run before, it may be used and should now enable you to choose the partition for saving the local configs and package cache. (If asked, there is no need to first unmount the partition, that would only be needed to allow installing on its parent disk.) 
If setup-alpine has already been used to configure the diskless system, the storage settings may be modified directly with <code>setup-lbu sdXY</code> and <code>mkdir /media/sdXY/cache ; setup-apkcache /media/sdXY/cache</code> 
7. If the partition is large enough, it can be useful to edit lbu.conf to uncomment and set <code>BACKUP_LIMIT=3</code>. For example, to allow reverting to a previous, working state if needed.
{{cmd| # apk add nano
# nano /etc/lbu/lbu.conf
}}
8. Finally, generate the first .apkovl file containing all the previous changes with [https://wiki.alpinelinux.org/wiki/Alpine_local_backup Alpine_local_backup], by executing <code>lbu commit</code>, so the customizations that were just made will persist a reboot.

From then on, whenever packages are installed or newly configured, and the changes should be kept, execute <code>lbu commit</code> again.

Notes:

* For a virtual machine, the '''[[Qemu#Live_mode|Qemu example]]''' shows how an ISO image can automatically boot with .apkovl customizations.
* [https://wiki.alpinelinux.org/wiki/Alpine_local_backup Alpine_local_backup] explains how to include custom files outside of <code>/etc</code> in the .apkovl file.
* [[Alpine_Linux_package_management#Local_Cache]] covers managing a local package cache.
** The packages get listed in /etc/apk/world which gets saved with the lbu, for them to be automatically installed when the live system boots.
* It's possible to load an APKOVL file from a webserver, by supplying a custom url with the <code>APKOVL</code> kernel boot parameter.
** If you don't have a web server you can run busybox's httpd temporarily to serve an .apkovl - <code>busybox httpd -p 127.0.0.1:80</code>.
* To customize the boot sequence further, one may refer to [[PXE_boot#Specifying_an_apkovl]] and [[How_to_make_a_custom_ISO_image_with_mkimage]].

== Committing changes ==

The <code>lbu</code> 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, <code>lbu</code> will generate a file named something like {{Path|<var>myboxname</var>.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.).
<pre>
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
</pre>

=== Creating an .apkovl "package" elsewhere than on the configured media ===

To "commit" changes, but override the destination of the generated apkovl file, use <code>lbu package</code> instead of <code>lbu commit</code>:

<pre>
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.
</pre>

=== 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 <code>lbu package</code> via SSH with {{Path|-}} as the apkovl name:

On the server:
<pre>
ssh root@client "lbu package -" >client.apkovl.tar.gz
</pre>

== Checking what will be added to your apkovl ==

<code>lbu status</code> lists what will be saved the next time you run <code>lbu commit</code>. 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 <code>-a</code> flag:

<pre>
usage: lbu status|st [-av]

Options:
-a Compare all files, not just since last commit.
-v show include and exclude lists.
</pre>

Another option is <code>lbu list</code>. This works like <code>lbu status -a</code> but the format of the output is a bit different. (It's strictly equivalent to <code>lbu package -v /dev/null</code>).

usage: lbu list|ls

A third option is <code>lbu diff</code>. This shows the same incremental changes that <code>lbu status</code> (without <code>-a</code>) 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 {{Path|/etc}}. 
e.g. {{Path|/root/.ssh/authorized_keys}} (used by <code>sshd</code> to authenticate ssh-users). Such files/folders can be added to lbu's ''include'' list with the following command:

<pre>
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.
</pre>

{{Note|This information used to be maintained in {{Path|/etc/lbu/include}}. Now it's maintained together with the ''exclude'' list in {{Path|/etc/apk/protected_paths.d/lbu.list}}. Either way, the command <code>lbu include</code> only modifies lbu's configuration.
You will need to run <code>lbu commit</code> to actually create/modify your apkovl.}}

== Exclude specific files/folders from the apkovl ==
Assume you have some files located in {{Path|/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 {{Path|/var/log/}} but in a location that would otherwise be tracked by <code>lbu</code>.
Such files/folders can be added to lbu's ''exclude'' list by manually editing the file or using the following command:
<pre>
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.
</pre>
{{Note|As stated above, this information is now maintained in {{Path|/etc/apk/protected_paths.d/lbu.list}}. The command <code>lbu exclude</code> also only modifies lbu's configuration. 
You will need to run <code>lbu commit</code> 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. {{Path|runme}} works, but {{Path|runme.sh}} does not.)

The scripts in {{Path|pre-package.d}} are run before apkovl is created. Scripts in {{Path|post-package.d}} are run after apkovl is created.

=== Example ===

Rather than adding the raw database directories to {{Path|/etc/lbu/include}}, you can do a "database dump". e.g. {{Pkg|postgresql}}:

* Create {{Path|/etc/lbu/pre-package.d/sqldump}} with the following contents: <pre>pg_dumpall -U postgres | gzip -c >/root/pgdatabases.gz</pre>
* Mark the file executable: <code>chmod +x /etc/lbu/pre-package.d/sqldump</code>
* Create {{Path|/etc/lbu/post-package.d/sqldumpdelete}} with the following contents: <pre>rm -f /root/pgdatabases.gz</pre>
* Mark the file executable: <code>chmod +x /etc/lbu/post-package.d/sqldumpdelete</code>
* Finally, add the database dump file to the list of files to back up: <code>lbu include root/pgdatabases.gz</code>

Now when you do a <code>lbu commit</code>, the sql databases are dumped and gzipped to {{Path|/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 {{Path|/root}} directory, where it can be restored manually.

== Multiple backup versions ==
Lbu can now keep multiple backups so you can revert back to older configurations.
Set BACKUP_LIMIT in {{Path|/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:

{{Cmd|lbu list-backup [<media>]}}

and you can revert to an older one with:

{{Cmd|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.

== See also ==
* [[Back Up a Flash Memory Installation]]
* [[Manually editing a existing apkovl]]

[[Category:Installation]]

[[Category:Booting]]
[[Category:Package Manager]]
[[category: LBU]]

Alpine Linux - User contributions [en]

Alpine local backup