switch_root usage
MikeB
mabnhdev at gmail.com
Sun Jun 24 16:20:07 UTC 2018
I'm using switch_root from busybox 1.28 on a fairly generic Linux 4.14
embedded system.
I have two issues that I'm looking for advice on.
Up until now I've been running out of initramfs, but it's getting kind
of big and I'm trying to reduce the memory usage. So, I created a
block-based root disk and started using switch_root early in boot. So
far, so good.
However, I see almost no difference in memory usage after the
switch_root (looking at slabtop and /proc/meminfo). I was hoping to
see a dramatic decrease in memory usage just freeing up all the
contents of the initramfs. All the stats I've seen make me think
little or none of the initramfs contents have actually been deleted.
I haven't come up with a good way to debug in that environment. Any
thoughts about this would be appreciated.
Also, I'm wondering about the proper way to deal with the pseudo
filesystems (devfs, procfs, tmpfs, etc) when using switch_root. As
far as I can tell, none of these filesystems are accessible after the
switch_root. I've been unmounting them before switch_root, then
re-mounting them after switch_root and that seems to work fine, but
I'm wondering if I'm doing the right thing. I read one post that
indicated that all these were left mounted and were still accessible
after the switch_root. I tried that, but no luck. Am I correct in
unmounting/switch_root/re-mounting for these filesystems?
Thanks for any help.
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