Re: [gentoo-amd64] Re: system broken?

[Martin Herrman]

On Wed, Dec 10, 2008 at 2:45 PM, Duncan <1i5t5.duncan@×××.net> wrote:

> Well, you can, but not directly.
>
> Surely you have an emergency boot method, either (like me) a backup root
> partition that you snapshot from your working one periodically when you
> know the system's working pretty smoothly (which means you've rebooted
> since your last merges so you know you can), or a LiveCD of some sort,
> maybe a Gentoo LiveCD, maybe something else, that you can boot to and
> mount your broken system partitions from?  That's the basis from which to
> start.  If you don't have such an emergency boot solution, how do you
> expect to recover in the event you have a broken boot?
>
> When I had a problem with glibc and needed to downgrade, I simply stuck
> the appropriate root=/dev/whatever on the kernel command line from grub,
> and booted to my backup root partition.  The way I'm setup, that gives me
> the exact working system I had at that point, and can mount either my
> normal or backup /home and other data partitions, so I'm still fully
> operational.  I was able to mount my my normal root from the backup,
> along with my packages partition, then set ROOT= to point to the normal
> working partition, and emerge -K an appropriate binpkged glibc over top
> of the broken one.  I must admit I was a bit apprehensive about it as I'd
> never used portage's ROOT= setting before, and after all this is glibc
> we're talking about, but it worked fine, and I was then able to reboot
> back into my normal root again.
>
> Another alternative as long as glibc isn't so broken you can't run
> anything, is to hand-edit the ebuild to kill the downgrade blocker bit of
> the script.
>
> Finally, as posted elsewhere, it's also possible to start with a stage
> tarball once again as a known good starting point, then emerge --
> emptytree @system to get back to a current system.  This is sort of the
> equivalent of an OS reinstall on other OSs/distributions and it works
> quite well.  Of course, it helps if you make a backup of your /etc before
> you do it, so you can quickly recover overwritten config files.
>
> So there's ways to downgrade glibc.  You just have to be smarter than the
> child-safety-locks portage has in place to prevent you from doing it
> inadvertently and breaking a system further, as doing so after remerging
> a bunch of packages thus linking them to the new glibc might do.  But if
> you have a backup to operate from if necessary, you don't have to worry
> so much about breaking a system which is probably already partially
> broken or you'd not be having to worry about downgrading glibc.

Well, this is why I actually love Linux: you still have control over
your system, no matter what happened. But.. the downside is that you
need to know how things work :-) For the moment, I have chosen the
most easiest way:

sys-apps/portage
app-admin/eselect-news
app-admin/eselect

added to package.keywords. That went smooth and everything seems to
work again (altough it adds the number of masked packages, which is a
risk). But.. I should now keep an eye on the development of glibc and
portage (etc.) packages so I can get back to the stable tree again?
Can it take months before gcc 4.3 and glibc 2.8 are stable?

Martin