How can I add custom initramfs hooks in Slackware like it can be done by modifying files inside /etc/initcpio/hooks in Arch Linux?

run mkinitrd -c ... ... as usual.
make your desired changes to the stuff in /boot/initrd-tree
run mkinitrd ... ... again, this time without the '-c' option.

Slackware doesn't have a "hooks" framework built into the initrd stuff.

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You should continue with if the OP intends to reuse his initrd modifications for another initrd (i.e. for another kernel), he should reapply all modifications BY HAND on the new initrd tree. Which is a real hassle of time and errors prone.

Apparently, they believes that their initrd is absolutely perfect, it covers absolutely all use cases and nobody ever needs to modify it...

However, see this thread for more explanations about what could possible go wrong: https://www.linuxquestions.org/quest...it-4175655412/

From "mkinitrd -h":
I see nothing in that thread that tells me what could go wrong. More and more people however, seem want to sit on their hands, requesting that Slackware do everything for them, and thus compromise the simplicity of this distro in an attempt to make it look more than Arch, or Ubuntu.
Another takeaway from the script-kiddie invasion is that I see more of the asking / demanding type of posts, and less of the 'here is a patch that will add desired behaviour' kind of posts. Obviously, the former is not going to help anyone, while the latter is how - historically - new functionality got added to Slackware.

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When I was using a custom initrd I just made a script that did this:

mkinitrd -c blah blah
patch /boot/initrd-tree/init patchfile.patch
mkinitrd blah blah

That way I didn't have to concern myself with reapplying my changes. Slackware's mkinitrd could be improved, but it's really not as big a deal as you're making it.

Anyway, repeatedly complaining gets you nowhere. This is open source. If you don't like something fix it yourself. The code in the initrd that handles unlocking of multiple luks devices originally came from me: I had a need to do that and it wasn't supported, so I fixed it. It was eventually adopted into the stock package. You don't have to be a slackware team member to contribute, many of us have, and you only need to look at the changelog to see all the acknowledgements. Ofcourse, it helps if you're respectful. No one wants to deal with someone who makes it a habit to be a dick.

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Hope this helps, mkinitrd has '-s' and '-o' options to use separate source trees and output initrd.gz files.

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