Chroot: illegal instruction

avdb · n00b Joined: 16 Aug 2020 Posts: 65 Location: Netherlands

I know what the problem is, I compiled my entire system for a certain micro-architecture with really specific CPU flags, I switched to a different micro-architecture which is incompatible with my old system and now I can't boot nor chroot anymore (meaning I can't look what packages I have installed).

My question is, how do I reinstall everything again without losing any data? I know that I'm going to have to recompile everything but I don't want to lose any configuration files.

eccerr0r · Posted: Sat Jan 02, 2021 8:31 am Post subject:

Conundrum.

Well you can always grab your world file in /var/lib/portage/world to get your package list to rebuild as well as grab your /etc files.

If you still have your old machine you could rebuild world with a common denominator architecture and then do it again with the new one.

You could setup another disk with an emulator to rebuild the system...

Still got some options but not very pleasant.
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Buffoon · Veteran Joined: 17 Jun 2015 Posts: 1369 Location: EU or US

Gentoo is no different from any other *nix system, system cofiguration files are in /etc, users have their configuration files in their home directories. World file was already mentioned above. All this should be part of your backups anyway.

Tony0945 · Posted: Sat Jan 02, 2021 4:24 pm Post subject:

I think this will work:

1. boot a rescue mediaum, mount your Gentoo root as /mnt/gentoo
2. backup world and extract a stage3 tarball over your /mnt/gentoo from the recue medium. AFAIK this is just @system
3. Now you should be able to chroot, change -march and emerge -e @world
4. After it's all up and running, emerge -a --depclean to cleanup anything from the tarball that you don't need.

Comments, anyone?

Hu · Administrator Joined: 06 Mar 2007 Posts: 21842

I think Tony's method has the potential to leave behind orphaned files. Consider the case that a package app-example/tool-1 is installed on the system, and is part of the stage3. Further, suppose that if built with USE=foo, it installs /usr/bin/foo-tool; if built with USE=-foo, then it does not. Suppose that the installed copy was built with USE=foo, and the stage3 is built with USE=-foo. Extracting the stage3 will overwrite the CONTENTS file, but not remove foo-tool. Now foo-tool exists, and Portage has no record of what owns it. Future upgrades/removals of app-example/tool will not know to touch it. Attempting to reinstall app-example/tool with USE=foo will trigger a collision because the file is not recorded as part of the old version. With the right FEATURES, Portage can ignore collisions where the to-be-replaced file is an orphan, which might clean this up if step 3 runs to completion.

Tony0945 · Posted: Sat Jan 02, 2021 6:39 pm Post subject:

Good analysis, Hu. I suppose the safest way is to backup /home, /etc and /usr/local and wipe the rest and reinstall. There would still be work to do to ensure that numerical users were the same.

Best of all (I did this going from bulldozer to ryzen): First emerge -e @world with -march=generic, then remove the drive, put it in the new machine and emerge -e @world with -march=native.

Buffoon · Veteran Joined: 17 Jun 2015 Posts: 1369 Location: EU or US

revdep-rebuild can find orphans, just to keep your system clean.

avdb · n00b Joined: 16 Aug 2020 Posts: 65 Location: Netherlands

Reinstalling went well, last issue I have to deal with is how do I force Portage to use locally fetched sources when compiling overnight? I noticed that after a few hours it refuses to compile your package with locally fetched sources unless it can confirm that it's the latest version which is pretty annoying since I turn my router off at night to save electricity.

avdb · n00b Joined: 16 Aug 2020 Posts: 65 Location: Netherlands

Oh and another thing, I have a qcow2 image that I want to copy over to my new root partition but Linux thinks that it's 100GB (didn't do that myself) when in reality it's only like 2GB. Any way I can resize these files without losing their contents when copying them over?

Tony0945 · Posted: Sat Jan 02, 2021 7:12 pm Post subject:

Buffoon · Veteran Joined: 17 Jun 2015 Posts: 1369 Location: EU or US

I have replaced hard drives many times for my Gentoo boxes, never used anything else than 'cp -a'. I know, there is no poetry in this. Just plain boring, fast command. It probably is much greater feeling to use some bloated sophisticated application for this ... With 'cp -a' you can use different filesystem, different size of partition, no limitations.

eccerr0r · Posted: Sat Jan 02, 2021 7:26 pm Post subject:

I've found that emerge -f sometimes misses files, which is annoying. Best is to leave it connected to the internet.
Heck I have multiple regular desktop machines powered up 24/7 like my PVR, not really that big a deal.

But portage will automatically use whatever's already downloaded, just make sure you don't emerge --sync and tell portage a new version is possibly available. Just make sure you do your upgrades and downloaded files promptly, don't wait a week.
_________________
Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching?

avdb · n00b Joined: 16 Aug 2020 Posts: 65 Location: Netherlands

Tony0945 · Posted: Sat Jan 02, 2021 7:49 pm Post subject:

apiaio · Guru Joined: 04 Dec 2008 Posts: 419

Buffoon · Veteran Joined: 17 Jun 2015 Posts: 1369 Location: EU or US

Router and wifi access point do not operate in same OSI layer, they have nothing to do with each other. :roll:

I turn often off my access point, I have everything wired and although it takes less than 10 W of power keeping it on is not justified, but I turn never off my router.

Hu · Administrator Joined: 06 Mar 2007 Posts: 21842

apiaio · Guru Joined: 04 Dec 2008 Posts: 419