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From: Jerome Marc <marcjero@yahoo.com>
Date: Mon, 30 May 2022 15:46:15 +0200
Message-ID: <CAD1Ag0y8K-mzP7-oYN0iAbM3aOHWnNbTp8bw8xgZs9r=M5R5QA@mail.gmail.com>
Subject: hybrid setup idea
To: ~alpine/users@lists.alpinelinux.org
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References: <CAD1Ag0y8K-mzP7-oYN0iAbM3aOHWnNbTp8bw8xgZs9r=M5R5QA.ref@mail.gmail.com>

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Hi all,

I'm running a diskless setup on a Raspberry PI. Problem is I am missing
memory because my SBC only has 512Mb sdram.
This is more than enough to run tiny things like nginx but I just tried to
install docker. About 200mb software installed, my root filesystem is
almost full.
I really like the diskless approach but I miss the system install for the
storage and memory capabilities.

So I wonder why can't we have both ? I have seen numerous examples of
mixing ext4 root fs with tmpfs mounts in order to keep the root fs
read-only.
That's interesting but very customized, not generic.

I had another idea that would leverage overlays. I could use a lower layer
stored in the sd card and an upper layer stored in tmpfs.
The lower layer could be read-only and filesystem write operations would be
applied to tmpfs only.

The question is how to maintain such a system ? Would be perfect if apk
could upgrade the lower layer. overlayfs doesn't support the lower layer
updates unfortunately.
I was thinking about this logic :
remount rw the lower layer fs -> chroot using the lower layer as root ->
run apk -> exit chroot ->  remount ro the lower layer fs -> remount the
overlay fs

I think it would be fairly easy to write a wrapper (apk-persist) to
automate everything.

btw I have seen an overlays folder in the boot partition of Alpine. What is
the purpose of this ?

Thank you

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<div dir=3D"ltr">Hi all,<div><br></div><div>I&#39;m running a diskless setu=
p on a Raspberry PI. Problem is I am missing memory because my SBC only has=
 512Mb sdram.</div><div>This is more than enough to run tiny things like ng=
inx but I just tried to install docker. About 200mb software installed, my =
root filesystem is almost full.</div><div>I really like the diskless approa=
ch but I miss the system install for the storage and memory capabilities.</=
div><div><br></div><div>So I wonder why can&#39;t we have both ? I have see=
n numerous=C2=A0examples of mixing ext4 root fs with tmpfs mounts in order =
to keep the root fs read-only.</div><div>That&#39;s interesting but very cu=
stomized, not generic.</div><div><br></div><div>I had another idea that wou=
ld leverage overlays. I could use a lower layer stored=C2=A0in the sd card =
and an upper layer stored in tmpfs.</div><div>The lower layer could be read=
-only and filesystem write operations would be applied to tmpfs only.</div>=
<div><br></div><div>The question=C2=A0is how to maintain such a system ? Wo=
uld be perfect if apk could upgrade the lower layer. overlayfs doesn&#39;t =
support the lower layer updates unfortunately.</div><div>I was thinking abo=
ut this logic :</div><div>remount rw the lower layer fs -&gt; chroot using =
the lower layer as root -&gt; run apk -&gt; exit chroot -&gt;=C2=A0 remount=
 ro the lower layer fs -&gt; remount the overlay fs</div><div><br></div><di=
v>I think it would be fairly easy to write a wrapper (apk-persist) to autom=
ate everything.</div><div><br></div><div>btw I have seen an overlays folder=
 in the boot partition of Alpine. What is the purpose of this ?</div><div><=
br></div><div>Thank you</div></div>

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