eldergods.org

This is a gentoo problem I hadn’t seen before:

Turns out, I needed to build with “-introspection” in order to build it again with “introspection”. Or maybe I could just globally disable introspection, but not sure what that would change, it looks like a Gnome thing. As usual I ended up with lots of Gnome and KDE installed, and really I still just use Enlightenment everywhere. If it wasn’t Enlightenment, it would be Windowmaker or something similar.

I sometimes have a need to take down a Linux host “hard”, that is, without the normal shutdown scripts.  Among other methods, I accomplish this with:

This is suboptimal (risks corruption), but it does the job. The hosts in this case have kernel modules that the normal “rmmod” would hang on forever, and since they have no console/ILO or IPMI or other power control I am forced to use this or some other trick to take down (reboot -f or sending a NOC person out on the floor are the other common methods, the latter being our last resort).

Because this immediately forces the kernel to reboot (assuming you have the “Magic SysRq” option in your kernel), using ssh becomes a problem, as the TCP connection dies without you getting a RST packet, so normal ssh and TCP timeout mechanisms apply, and it’ll take a few minutes for the host to come back up and issue a TCP RST in response to a keep alive message for that connection.

Now, every once in awhile I do something without giving it enough thought. That’s a kind way of saying I do something really dumb. Imagine, if you will trying to reboot a lot of machines via an “at” job. Further imagine that you decided to change your normal reboot/shutdown -r to the aforementioned sysrq-trigger trick.

Also interesting is that using sysrq-trigger doesn’t allow the at job to be removed from the queue before the machine is restarted, and will just say there until the job is allowed to exit normally.

I think you see what I did. Dumb. Thankfully there are a few seconds available between boot and when the job runs to remove the job from the queue.

The thing I like most about Gentoo is the extraordinary flexibility that portage allows to make a system the way you want.   Every once in awhile, I find something annoying however (this happens on every operating system, you’re hearing about this one because it was just the most recent).   Today’s case in point:  I found that several things depending on libselinux.so.1 despite my having “-selinux” in my global USE flags, and selinux disabled in the kernel.   One of the packages that depends on that library is coreutils (which includes mv, cp, ln, and many other things you can’t afford to be without)

How did this happen?  Because my /var/lib/portage/world file has a lot of packages in it that don’t really need to be there (they should be pulled in as dependancies of packages I do want, not in the way I have them.)   When I was migrating to this box, instead of just looking at the few hundred packages in world, I grabbed a list of everything I’d compiled, and used that to build my new box.   One result of that is that sys-libs/libselinux got compiled.  (At least, I think that’s how it happened.)   I noticed but didn’t think it was going to be a problem.  However, for some ebuilds (coreutils being the most important to me), if the selinux header files are installed on the box, the configure script detects files like /usr/include/selinux/flask.h and proceeds to include selinux support.   Then you will find that /bin/cp and many other critical utilities are linked against libselinux.so.1, so you can’t remove the sys-libs/libselinux, and since the USE flag has no effect other than changing RDEPEND in the ebuild, you’re stuck.   Catch-22, almost.

Today I finally resolved to fix this, because I got annoyed, and because sys-libs/libselinux is hard-masked after my latest sync (as a result of the sync and having to update my profile with eselect).

The first part, fixing coreutils is pretty easy:

Unfortunately, after that… you are still stuck.   The coreutils will work, but I was left with a number of packages that revdep-rebuild reports as missing libselinux.so.1… furthermore they all die when trying to link against libselinux:

/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.2/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lselinux

Ah, portage, why are you so cruel to me?    The above example is from gnome-terminal.  Good thing I still use xterm.

Note: the next part could help, but it’s far easier to use lafilefixer these days.

So, what to do?   I’m not kidding, this is basically it, in one line form:

find /usr/lib64 -name '*.la' -print | xargs grep selinux | cut -f1 -d: | sed -e 's#^./##g' | xargs equery b | awk '{print "="$1}' | sort -u | xargs emerge

Built that up a command at a time once I realized that the *.la files still contained references to the libselinux (-lselinux).  Basically, it searches for all the .la files that contain references to selinux.   .la files are just text files that control the linking process, either as part of libtool or the compile-time linker. My command above just uses some rather lame shell tricks to run emerge against all the packages those files belong too.

Even after that was complete, I still had libnss3.so.12 breakage to contend with, but at least revdep-rebuild was working at that point (not breaking on every ebuild it found missing libselinux.so.1).    Frustrating.

I hope this saves someone some damn time, somewhere.

Just got back from Linux World in San Francisco (actually, show ended on Thursday but I hung out until the 19th to visit friends.) Good show, but 6 days is a recent record for me being away from home, and it’s good to be back.

I focused on the HPC and kernel development tracks while I was there. In particular, I have several new things to experiment on that I saw there.

For starters, it became clear that I should probably get an AMD-based system for my OpenSolaris experiments. The demo machine I saw there with OpenSolaris with a Brandz CentOS lx zone on it seemed like a really decent machine, and while I’ve always liked SPARC, maybe it would be good to have both.

For the meantime, I will actually be playing with opensolaris on VMWare. Virtualization has been a pretty big topic lately, and at the conference I talked to SuSE (who’s distributing Xen), XenSource, VMWare (which I’ve been using since it was first available, and am currently using at work and at home), SWSoft (makers of OpenVZ/Virtuozzo) (which I’d managed to never hear about before somehow.)

I’ll have more to say about what I saw there. Next time I may even take pictures.