Local APK cache

2023-04-30T16:07:12Z

Dnpr:

=== Overview ===

To have the packages available during boot, apk can keep a cache of installed packages on a local disk.

Added packages can then be automatically (re-)installed from local media into RAM when booting, without requiring, and even before there is a network connection.

The cache can be stored on any writable media, or at the same location as the .apkovl file from the [[Alpine_local_backup| local backup utility <code>lbu</code>]].

=== Enabling Local Cache with current releases ===

Execute the script {{Cmd|setup-apkcache}} and it will assist in enabling a local cache.

The script creates a symlink named ''/etc/apk/cache'' that points to the cache directory.

{{Tip|On a diskless installation, to make the disk where the cache directory is present be automatically mounted at boot you can create an empty file ''.boot_repository'' inside the cache directory.}}

=== Cache maintenance ===

==== Removing older packages ====

When newer packages are added to the cache over time, the older versions of the packages default to remain in the cache directory.

The older versions of packages can be removed with the '''clean''' command. {{cmd|apk cache clean}} Or to see what is deleted include the verbose switch: {{cmd|apk -v cache clean}}

==== Download missing packages ====
If you accidentally delete packages from the cache directory, you can make sure they are there with the '''download''' command, {{cmd|apk cache download}}

==== Delete and download in one step ====
You can combine the two steps into one with the '''sync''' command - this cleans out old packages and downloads missing packages. {{cmd|apk cache -v sync}}

==== Automatically Cleaning Cache on Reboot ====
To automatically attempt to validate your cache on reboot, you can add the above command to a {{Path|/etc/local.d/*.stop}} file:

{{Cat|/etc/local.d/cache.stop|#!/bin/sh

# verify the local cache on shutdown
apk cache -v sync

# We should always return 0
return 0
}}

{{Tip|Usually the only time you need to reboot is when things have gone horribly wrong; so this is a "best effort" to cover forgetting to sync the cache; It is much better to run '''sync''' immediately after adding or upgrading packages.}}

{{Note|Custom shutdown commands were formerly added to a {{Path|/etc/conf.d/local}}; but that method is now deprecated.}}

=== Special Caching Configurations ===

==== Enabling Local Cache on HDD installs ====

Note that HDD 'sys' installs don't need an apk cache to maintain their state, it allows to serve packages over the network, though, e.g. to get installed by other local machines.

Manually create a cache dir and then symlink it to ''/etc/apk/cache'':
{{Cmd|mkdir -p /var/cache/apk
ln -s /var/cache/apk /etc/apk/cache}}

==== Local Cache on tmpfs volumes ====

In some circumstances it might be useful to have the cache reside on tmpfs, for example if you only wish for it to last as long as the system is up.

NOTE: ''apk'' is coded to ignore tmpfs caches, and this is correct behaviour in most instances. Using tmpfs as a package cache can consume large amounts of system memory if you install a lot of packages, possibly resulting in a crashed system. You can limit this by restricting the size of your cache to a small number (128M in the example below).

To do it, you need to create an image inside which your cache can live. We do this by creating an image file, formatting it with ext2, and mounting it at ''/etc/apk/cache''.
* apk add e2fsprogs
* dd if=/dev/zero of=/apkcache.img bs=1M count=128
* mkfs.ext2 -F /apkcache.img
* mkdir -p /etc/apk/cache
* mount -t ext2 /apkcache.img /etc/apk/cache
* apk update

As usual, if you want to download currently installed packages into the cache, use ''apk cache sync''.

==== Manually Enabling Local Cache (required for releases prior to v2.3) ====

# Create a '''cache''' directory on the storage device where you keep the lbu backups (typically, <code>/dev/sda1</code>.) {{Cmd| mkdir /media/sda1/cache }}
{{Tip|If you get an error that says "mkdir: can't create directory '/media/usbdisk/cache': Read-only file system", then you probably need to remount your disk read-write temporarily. Try {{Cmd|mount -o remount,rw /media/sda1}} and then don't forget to run {{Cmd|mount -o remount,ro /media/sda1}} when you are done with the following commands}}
# Create a symlink to this directory from <code>/etc/apk/cache</code>. {{Cmd|ln -s /media/sda1/cache /etc/apk/cache}}
# Run an lbu commit to save the change (<code>/etc/apk/cache</code> is in <code>/etc</code> and is automatically backed up.) {{Cmd|lbu commit}}
{{Tip|If you needed to remount your disk read-write before, run {{Cmd|mount -o remount,ro /media/sda1}} now that you are done with saving the changes}}

Now whenever you run an apk command that pulls a new package from a remote repository, the package is stored on your local media. On startup, Alpine Linux will check the local cache for new packages, and will install them if available.



[[Category:Package Manager]]

Alpine Linux - User contributions [en]

Local APK cache