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Date: Sun, 15 Jan 2023 21:20:49 +0100
Message-Id: <CPT1K6SS7MJB.11OX1R7M79RF6@unicorn-x220.lan>
Subject: loading an apkovl from an external USB stick
From: "Unicorn" <unicorn@regrow.earth>
To: <~alpine/users@lists.alpinelinux.org>

Hello,

I am trying to learn to make proper use of the power of lbu and apkovl with=
 my ARM SBC, but I am confused by a few things here.
Firstly, the "apkovl" kernel cmdline option is quite poorly documented, at =
least I could only find one somewhat complete documentation in the wiki, in=
 the PXE boot article [0]. However I do not seem to be able to get one of t=
he mentioned formats to work.

A bit of background: I have the generic ARM archive extracted to mmcblk0p1,=
 so it boots from that partition. I then tried to save/load the apkovl file=
 from the second partition, mmcblk0p2. I was able to achieve this with the =
following kernel cmdline option:
apkovl=3D/media/mmcblk0p2/myhostname.apkovl.tar.gz

I assume that this only works because the partition is automatically mounte=
d there at boot. If somebody can also explain what determines which partiti=
ons get automatically mounted, please enlighten me, because this is already=
 quite confusing to me. :)

Now I tried to save/load the apkovl from an external USB stick on the sda1 =
partition. I noticed that this partition does NOT get automatically mounted=
 in /media/, so the previous solution does not work. However the other form=
ats that are mentioned in the abovementioned article [0] also do not work. =
I tried the following:
apkovl=3Dsda1
apkovl=3Dsda1:vfat:/myhostname.apkovl.tar.gz
apkovl=3Dsda1:vfat:myhostname.apkovl.tar.gz
apkovl=3Dsda1:myhostname.apkovl.tar.gz

These should work according to the explanation on that page, but do not.

I asked on IRC and ikke linked the code of the initramfs-init.in file of mk=
initfs to me [1], however I do not see support for this syntax in that file=
. So either the wiki is wrong here, or this is already handled by something=
 else before the $KOPT_apkovl variable gets used by the script.

I would really appreciate advice on how the automatic mounting of partition=
s in /media/ actually works and how the apkovl option is correctly used. I'=
ll happily contribute my learnings back to the wiki. :)

Thanks,
Edin

[0] https://wiki.alpinelinux.org/wiki/PXE_boot
[1] https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/master/initramfs-=
init.in#L42