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mini-HOWTO: repairing a broken toolchain without binpkgs
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Ant P.
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Joined: 18 Apr 2009
Posts: 6920

PostPosted: Thu Jan 01, 2015 7:45 pm    Post subject: mini-HOWTO: repairing a broken toolchain without binpkgs Reply with quote

Just thought I'd write this down for the benefit of others...

Boring background details:
I was trying to update GCC 4.8.3 -> 4.8.4 on one machine using `cave resolve -1x gcc`.
It gets all the way to the end, then fails halfway through unmerging the old version (as it has been doing for weeks now - who's supposed to be QA'ing this?)
Usually I clean up the wreckage by doing `gcc-config -l 2; source /etc/profile; cave resolve -1x gcc` and waiting for it all over again, but today I tried to be clever. So I ran `cave resolve -1x gcc --skip-until-phase src_install`.
Oh wait, that was wrong, let's try again with `--skip-until-phase merge`... Whoops, too late.
The first command dutifully cleaned up the build dir and exited, and the second one did exactly as it was instructed and skipped the compile, merged all 0 files it found, and removed the old gcc entirely.

======

So, I have a borked machine with no GCC and no libstdc++.so.6.

I do have another machine and plenty of options, so I did this:
Code:
mkdir /mnt/remote
sshfs root@$remote_machine:/ /mnt/remote
# I tried NFS first here but mount.nfs kept hanging; sshfs will work just as well though.

DISTDIR=$local_distdir emerge --fetchonly gcc
# I'm not sure what's going on here, but portage gets horribly confused when $ROOT is used and it tries to download files.
# Making sure both sides have all the distfiles beforehand fixed it.

DISTDIR=$local_distdir ROOT=/mnt/remote CFLAGS="-O2 -pipe -march=$remote_cpu" emerge -av gcc
# I used -march=btver1 from a -march=amdfam10 host here without problems, it should be safe as long as $(uname -m) is the same.

ssh root@$remote_machine gcc-config -l
 [1] x86_64-pc-linux-gnu-4.8.4 *

And it works!
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steveL
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Joined: 13 Sep 2006
Posts: 5153
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PostPosted: Thu Jan 01, 2015 8:48 pm    Post subject: Reply with quote

Yay for emerge ;)

sshfs is cool yeah; you can use it for distfiles on a LAN-server, too, though I've forgotten most of that setup, and didn't write it up.
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Ant P.
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Joined: 18 Apr 2009
Posts: 6920

PostPosted: Fri Jan 02, 2015 3:14 am    Post subject: Reply with quote

I should've been more specific: once things seem to work, rebuild the affected packages properly!

I didn't do that, and went off to update @world, then started getting a few "weird" segfaults in C++ binaries. An emerge -e on their owning packages straightened that all out, but it burned a few hours of CPU time.

Well in any case this could've gone worse; I got to test my backup plans if nothing else :lol:

----

edit: hmm, maybe I *was* right. I'm getting exactly the same segfault on a totally unrelated remote server...
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yoshi314
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Joined: 30 Dec 2004
Posts: 850
Location: PL

PostPosted: Mon Jan 05, 2015 1:50 pm    Post subject: Reply with quote

interestingly i had the same problem with unmerge of gcc, i thought it was power failure.

in my case i just switched gcc with gcc-config and assumed that old version was uninstalled already. That was enough to restore libstdc++ and get things running.
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