Count Upgradable Packages on Alpine Linux

I like to use Alpine Linux for cloud servers because it’s extremely small, so I don’t have to add extra RAM just to run the operating system. But I like knowing when updated packages are available.

You need root to update the local list of available packages first, but that can be automated safely (see below):

doas apk update

Just asking Alpine is easy, and doesn’t require extra permissions:

apk list -u

That gives you a detailed list of upgradable packages. Or to get a quieter result with just the names:

apk list -uq

And this being Linux, it’s easy to get a word count with wc (yes, it’ll count hyphenated package names as a single word):

apk list -uq | wc -w

Automating the List Updates

To get APK to update its package list daily, I’ve put the following in /etc/periodic/daily/apk-update.sh:

#!/bin/sh
apk update

That doesn’t install anything, so it’s safe to let it check on a daily basis. Of course that doesn’t tell me anything, it just makes sure the list is relatively current when I ask it.

I assume if you’re using Alpine you know how to set file ownership/permissions. Scripts in /etc/periodic/daily should be owned by root, executable, and not writeable by other users. For example:

doas chown root:root apk-update.sh && doas chmod 755 apk-update.sh

Friendly Reports on Login

For the actual report, I’ve written a short shell script (kept simple so it’ll run in busybox) called count-apk.sh to give me the count and names, but only if there aren’t too many of them:

#!/bin/sh                                                                                      
UPGRADABLE=`apk list -qu`
COUNT=`echo "$UPGRADABLE" | wc -w`
if [ $COUNT -gt 9 ]; then
	echo $COUNT packages available to upgrade.
elif [ $COUNT -gt 1 ]; then
	echo $COUNT packages available to upgrade:
	printf '%s\n' "$UPGRADABLE"
elif [ $COUNT -gt 0 ]; then
	echo 1 package available to upgrade:
	printf '%s\n' "$UPGRADABLE"
else
	echo No packages available to upgrade.
fi

And to get that reported every time I log in, I’ve put it in my ~/.profile.

~/bin/count-apk.sh

Meanwhile I’ve been trying to decide how much I want to automate maintenance on these systems. I don’t want to auto-update everything and risk breaking changes, but I don’t want to have to log into every internet-reachable virtual server on a weekly basis to keep it current either.