Upgrading a year-old Arch Linux installation
Tonight I had some fun dealing with Arch Linux. Some of my friends like to joke about Gentoo (which I've been using for more than four years on my laptops now) being a Tamagotchi. While there might be some truth in those jokes, my own experience indicates that Arch Linux (which has a significantly higher number of users among the people I know) has become orders of magnitude worse in this respect, at least during the past couple of years.
As the title of this post indicates, the installation in question was an Arch Linux on my girlfriend's computer which hadn't been touched for nearly one year. That means it was from times before the Arch maintainers shoved systemd down everyone's throat and started doing all the other stuff just to imitate the best ideas Lennart & co. appear to be bent on dictating to everyone.
In other words, the system was still using sysvinit and the good old Arch initscripts, it had separate /bin, /sbin and /usr/sbin and a fairly extensive collection of rather ancient packages installed on it.
I was forced to go through a similar procedure about half a year ago when I had to make a fresh release of OI-Live. At that time I had to get a virtual machine to an up-to-date state. This virtual machine only served as a template from which I created a new image once per year, which usually meant dusting off the machine, one run of pacman -Syu, pacdiffviewer, build a custom kernel, busybox and maybe a few other tools, set a new default KDE wallpaper, create a squashfs and voilà.
During the last few years, there was all the shuffling around in the filesystem in Arch, so just to be on the safe side, I created a snapshot of the virtual machine and tried to make the jump in one try. I ended up with a system where there was no /lib/ld-linux.so.2, which basically meant that the only way to run a command was to prepend /usr/lib/ld-linux.so.2 to it. So, forget about any shell scripts or calls like system or exec. I kept trying to resuscitate the system for a while, until I found out about a handy thing: the Arch Rollback Machine.
In the end I just ditched the broken virtual machine, restored it from the snapshot I had taken earlier and performed the upgrade in about five steps, each one between two manual interventions.
This time I was working directly on bare metal, so no snapshots. I thought it should still be quite painless though, since I was planning to just do the same thing as with my virtual machine: just shove the right date in the mirrorlist into the Rollback Machinge entry and perform pacman -Syu repeatedly.
So that's what I did. I copied over the ARM URL from the wiki, put in "2013-01-20" as the date and ran pacman -Sy. Crap, 404 not found. What the... Oh great, apparently the old ARM has been discontinued and removed from the face of the Earth and while there is a replacement, it only holds an archive for the past couple of months. Fantastic.
That meant we had no choice but to go through the following changes in one go:
- migration to systemd
- migration of the /lib symlink from glibc to filesystem
- migration of binaries into /usr/bin
- and, as it turned out, a few extra stabs in the back, such as KDE package renames which are no longer marked in the repositories, resulting in extensive file conflicts etc.
The funny thing about this is that while the second item required that filesystem and glibc be both updated at the same time, the description of the third item suggests upgrading glibc all by itself. Like... Wat? And these two changes aren't even that far away from each other in time.
To be honest, the first item was achievable beforehand; even though the system wasn't migrated to systemd yet, the package was already in place, so that's the first thing I did. I added the init=/usr/lib/systemd/systemd (ugh) parameter to /etc/default/grub, ran grub-mkconfig -o /boot/grub/grub.cfg, rebooted, enabled all necessary services using systemctl and all seemed to be running more or less okay.
All right then, on to the update. In the first attempt I tried to just pacman -Syu, just in case the whole upgrade might just succeed. I was fairly sure, though, that there would be at least some file conflicts and, of course, I was right. There was a conflict between filesystem and /bin, /sbin and /usr/sbin. That was not the only one though – I got a whole lot of other conflicts in KDE packages. This is the fourth item in the above list.
At first I tried to individually remove the conflicting old KDE packages. Of course, other packages were dependent on them, which means I had to force pacman to ignore those dependencies. According to the version of pacman(8) that was in place, the -d flag is supposed to do just that. Except that it didn't. Apparently I missed the part about the flag having to be present twice.
Anyway, after a while I realized that there may be other KDE packages that don't have any conflicts but have been dropped or something, which may leave some junk in /bin or /usr/sbin, so in the end I decided to just uninstall all of KDE and reinstall it after a successful upgrade.
Okay, with KDE out of the way, there was only the annoying conflict in the filesystem package. Since I had to upgrade both filesystem and glibc at the same time and I couldn't upgrade filesystem right then, the obvious choice was pacman -Su --ignore filesystem,glibc. Well, guess what. Nope. A bunch of packages required a newer version of glibc, among them, pacman. All right then, pacman -Sud --ignore filesystem,glibc,pacman.
Phew, no more conflicts and it seemed to actually do something. Of course, with bash moved to /usr/bin/bash, it was no longer possible to execute any preinst/postinst scripts, but whatever, I could always just reinstall all packages later. The important thing was that stuff was actually moving away from all the (s?)bin directories.
Okay, finished. Now just to upgrade the remaining packages and all should be all right. So, pacman -Su:
pacman: error while loading shared libraries: libarchive.so.12: cannot open shared object file: No such file or directory
Crap. At this point I almost gave up. However, being myself, I gave it one more shot, so I downloaded the current version of pacman, unpacked the pacman binary, the required libalpm.so.8 and moved them into /usr/bin and /usr/lib respectively. Hooray, I can run pacman again.
So, seeing that I could now run the newer version of pacman, even though I still had the older version of glibc (which I was afraid would render pacman impossible to exec or something), I tried to just reinstall pacman itself, leaving glibc and filesystem as the last ones.
Obviously, pacman complained about a conflict with the existing files for libalpm.so.8, which I had extracted a few minutes ago. It would be quite safe to just force overwrite them, though. Unfortunately, as soon as I gave pacman the -f of --force flag, it would just give me a very helpful error message, something along the lines of error: invalid flag.
I worked around this eventually by extracting the pacman package to /tmp/pacman, removing libalpm.so.8 from /usr/lib and executing pacman from /tmp/pacman/usr/bin with LD_LIBRARY_PATH=/tmp/pacman/usr/lib.
Hooray, the list of packages waiting for an upgrade had finally shrunk to glibc and filesystem. However, just pacman -Su still didn't work, there were still leftovers in the various (s?)bin directories.
I took a look at what was remaining in /bin, /sbin and /usr/sbin and I found a bunch of glibc-related binaries, some initscripts stuff and some consolekit junk. I just sent consolekit packing (who would want that stuff hanging around, especially since it wasn't the dependency of anything anymore), removed all initscripts-related packages (I didn't need those anymore, since there was systemd now), but I had no idea what to do about glibc.
By then I was mildly out of patience, so I just moved /sbin and /usr/sbin out of the way, performed pacman -Su which finally did what I wanted, verified all the binaries I had moved out of the way were properly installed again and removed the last traces of the old glibc package.
Wow, upgrade finished! I was honestly surprised I was able to pull this off. When I got that error message about libarchive.so.12, I was almost sure I would have to reinstall the whole thing from scratch.
The story is still far from over, though, so read on.
Now that I had the up-to-date packages of filesystem, glibc and others, there was still a bunch of packages whose pre/postinst scripts hadn't been run during their upgrade because of missing /bin/bash. That's easy, just reinstall them all and all should be OK.
The Arch wiki page on pacman tips gives a recipe to reinstall all packages: pacman -Qenq | pacman -S -, so that's what I did. I was surprised though, that this only wanted to reinstall about 150 packages while the upgrade I had just finished had upgraded mode than 500 packages. After a bit of digging around in the documentation I found out that the correct recipe is this one: pacman -Qnq | pacman -S - – I didn't want only explicitly installed packages, I wanted all of them.
Okay, now only to reinstall KDE and all should be done. Obviously, there was a new systemd version, new udev, new kernel etc, so I tried to reboot.
And this was the final kick in the gut. Of course, the system wouldn't boot. As a matter of fact, even the Windows chainloader entry had disappeared from grub.cfg.
Obviously, as part of an upgrade of the grub package, the old /etc/default/grub had been renamed to /etc/default/grub.pacsave, a default one had been installed and used to create a new grub.cfg. The same /etc/default/grub where I had put the init=/usr/lib/systemd/systemd kernel commandline argument. Since I had uninstalled all sysvinit- and initscripts-related packages, there was no /sbin/init anymore. Whoever is the maintainer of the grub package, thanks awfully. It's great that even though every other package saves new config files as .pacnew and leaves the old ones in place, yours installs the default automatically and even takes it one step further and applies it to the bootloader.
So, yeah, I had to boot SysRescCd, chroot into the system, put the right /etc/default/grub into place and regenerate grub.cfg and just for good measure, install systemd-sysvinitcompat.
Moral of this story?
Well, I got to know Arch Linux about four years ago, back when it was a rather nice, minimalistic, junk-free distribution which appeared to honor a statement I had read in the installation guide I was following: that Arch Linux was about the freedom of choice and that it was trying to give its users full control over the system.
These days? To put it bluntly, I honestly believe that during the last year I have spent more time trying to resuscitate Arch Linux systems (which got into a fairly broken state just because the maintainers aren't interested in giving their users safe upgrade paths over longer periods), than I have spent on other systems summed together in my whole lifetime. And believe me, I've managed to do some fairly exotic things back in the day, such as qemu /dev/hda.
If the arch maintainers are so keen on acting as lab rats for all those fantastic ideas folks at Red Hat come up with, let them be my guests. I know I won't install Arch on any machine in the foreseeable future and will strongly advise other people against doing so as well. If I'll ever want a Lennart-systemd-freedesktop-consolekit-or-whatever-the-new-cool-thing-is-enabled Linux distro, I'd sooner install Red Hat which seems to give at least a semblance of a shadow of stability. (Hint: not gonna happen.)
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