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turtles
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Joined: 31 Dec 2004
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 Posted: Sun Oct 27, 2024 6:17 am Post subject: dracut failed, droped to shell how to finish booting? |
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Greetings Gentooers
I am setting up a new Gentoo system (on bare metal) and usually make a initrd by hand for encrypted root but its been quite a few years and hand rolling was always tedious compiling stuff with static-libs then recompiling without so figured I'd try out Dracut.
This install has a encrypted root inside an LVM logical volume. I know the volume and encrypted root are good because I can mount them from the live USB. And I do realize this is the reverse of the Gentoo way of putting lvm in the encrypted drive, but this is just a router appliance and I digress.
Things have not gone very smoothly with Dracut, at first I assumed dracut would copy over the needed kernel modules but it does not seem to do that.
Also it throws allot of systemd-cryptsetup not found errors even after I configured it
| Code: | hostonly="yes"
# Equivalent to -a "module"
add_dracutmodules+=" lvm crypt " # Note leading and trailing spaces
omit_drivers+=" systemd systemd-cryptsetup bluetooth "
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After I reconfigured the kernel like I used to with all the Lvm and Crypt stuff BLK_DEV_CRYPTOLOOP CONFIG_DM_CRYPT ... compiled into the kernel (not as modules but compiled in) Dracut was getting closer telling me my /dev/mapper/gentoo_root does not exist.
After somehow dropping to the Dracut rescue shell (which is apparently not busybox?) I can poke around and see something named my /dev/mappter/gentoo_root something slightly different, it prefixed the logical volume name.
So I was finally able to manually unlock my root partition and mount it under /sysroot
Poking around I could see it mounted and my files were there.
I then tried | Code: | | exec switch_root /sysroot /sbin/init |
with no dice.
I possibly forgot to unmount proc sys and dev
So my question, how to you , finish booting from a Dracut rescue shell?
Should | Code: | | exec switch_root /sysroot /sbin/init |
work?
Thanks in advance
Docs I have used now and in the past:
https://wiki.gentoo.org/wiki/Dracut
https://wiki.gentoo.org/wiki/Dm-crypt
https://wiki.gentoo.org/wiki/LVM
https://wiki.gentoo.org/wiki/Custom_Initramfs
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Zucca
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Joined: 14 Jun 2007
Posts: 3671
Location: Rasi, Finland
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| Posted: Sun Oct 27, 2024 8:53 am Post subject: |
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Does the switch_root command give you any errors?
IIRC switch_root won't work unless it was exec'd from PID 1. And in case of busybox, I remember it didn't print any useful information if it failed in such way.
If you exit the rescue shell and you don't get kernel panic, it means it wasn't PID 1, and thus you cannot switch_root from there. Then you need to set the environment as such that dracut can continue booting (which is a limitation in my opinion).
BTW, if you want, you could try using my cinitramfs, which helps you create your own initramfs image (no static binaries needed necessarily).
It's very much WIP still. It works by reading a list of files, modules, etc from standard input and the outputs a cpio image. It handles most of the dependencies for C programs and modules at least. The extras directory contains example initramfs init script too. But you can write your own.
I'm using cinitramfs on all of my Gentoo setups which all use lvm/device mapper, but no ecryption. But it should work if you include all the commands required to unlock the filesystem.
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Last edited by Zucca on Sun Oct 27, 2024 3:16 pm; edited 1 time in total |
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grknight
Retired Dev
Joined: 20 Feb 2015
Posts: 1896
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| Posted: Sun Oct 27, 2024 1:37 pm Post subject: |
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| turtles wrote: | | Code: | | omit_drivers+=" systemd systemd-cryptsetup bluetooth " |
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This line is wrong. omit_drivers is for kernel modules when you are listing dracut modules.
Perhaps you mean omit_dracutmodules instead.
I cannot comment on other crypt stuff though. |
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zen_desu
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Joined: 25 Oct 2024
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turtles
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Joined: 31 Dec 2004
Posts: 1683
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| Posted: Sun Oct 27, 2024 5:26 pm Post subject: |
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| Zucca wrote: | Does the switch_root command give you any errors?
IIRC switch_root won't work unless it was exec'd from PID 1. And in case of busybox, I remember it didn't print any useful information if it failed in such way.
If you exit the rescue shell and you don't get kernel panic, it means it wasn't PID 1, and thus you cannot switch_root from there. Then you need to set the environment as such that dracut can continue booting (which is a limitation in my opinion).
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OK just tried it again
This time I confirmed my /root partition got opened by cryptsetup but again got named based on its uuid and dracut failed to mount it.
I got dropped to the dracut shell (which I am not sure what keys to press to get to)
I mounted my root partition at /sysroot
then ran
| Code: | umount /proc
umount /sys
umount /dev
exec switch_root /sysroot /sbin/init
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Then dracut goes into a infinate loop I had to snap a photo with my phone to catch the error
| Code: |
/lib/dracut-lib.sh: line 201 dracut-getarg: command not found
/lib/dracut-lib.sh: line 72: /dev/kmsg: No such file or directory
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I am sure I'll figure out the weird naming issue it like dracut needs a cryptab file, its not getting the setting correct.
But I am just currious for me in the future and other users is it possible to continue booting from the dracut cmd line?
Like when grub fails you can get into the grub cmd line and fix a issue keep booting.
Thanks
| Zucca wrote: |
BTW, if you want, you could try using my cinitramfs, which helps you create your own initramfs image (no static binaries needed necessarily).
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Thanks I'll check that out
I am curious about Dracut as I'll need to use it at work also
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turtles
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Joined: 31 Dec 2004
Posts: 1683
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| Posted: Sun Oct 27, 2024 5:29 pm Post subject: |
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| grknight wrote: | | turtles wrote: | | Code: | | omit_drivers+=" systemd systemd-cryptsetup bluetooth " |
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This line is wrong. omit_drivers is for kernel modules when you are listing dracut modules.
Perhaps you mean omit_dracutmodules instead.
I cannot comment on other crypt stuff though. |
Thank you that eliminited the systemd errors when dracut ran.
Which eliminated that as a possible issue.
Its an openRC system, so no systemd stuff.
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zen_desu
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Joined: 25 Oct 2024
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| Posted: Sun Oct 27, 2024 5:33 pm Post subject: |
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| turtles wrote: | | Zucca wrote: | Does the switch_root command give you any errors?
IIRC switch_root won't work unless it was exec'd from PID 1. And in case of busybox, I remember it didn't print any useful information if it failed in such way.
If you exit the rescue shell and you don't get kernel panic, it means it wasn't PID 1, and thus you cannot switch_root from there. Then you need to set the environment as such that dracut can continue booting (which is a limitation in my opinion).
|
OK just tried it again
This time I confirmed my /root partition got opened by cryptsetup but again got named based on its uuid and dracut failed to mount it.
I got dropped to the dracut shell (which I am not sure what keys to press to get to)
I mounted my root partition at /sysroot
then ran
| Code: | umount /proc
umount /sys
umount /dev
exec switch_root /sysroot /sbin/init
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Then dracut goes into a infinate loop I had to snap a photo with my phone to catch the error
| Code: |
/lib/dracut-lib.sh: line 201 dracut-getarg: command not found
/lib/dracut-lib.sh: line 72: /dev/kmsg: No such file or directory
|
I am sure I'll figure out the weird naming issue it like dracut needs a cryptab file, its not getting the setting correct.
But I am just currious for me in the future and other users is it possible to continue booting from the dracut cmd line?
Like when grub fails you can get into the grub cmd line and fix a issue keep booting.
Thanks
|
You can't manually switch_root in most cases because it must be executed as PID1, if your shell is not the init process, this will not function.
I'm pretty sure the crypttab stuff requires systemd integration. If you do not have systemd modules in Dracut, that will not be processed. Dracut generally relies on luks volume info being passed in the kernel command line.
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