Linux on Noetic Nought

Restoring a broken Ubuntu upgrade

Wed, 20 Nov 2024 15:17:00 +0530

A couple of weeks ago, Shantanu and I were discussing Ubuntu upgrades – his upgrade was borked and he ended up re-installing his system. I was celebrating the fact that I never really had to throw away my OS installation entirely since I switched to Ubuntu after getting tired of Arch Linux in 2011-12.

And on cue, I had a really broken update on my dad’s laptop! It was really broken – no WiFi, no Ethernet connection, no GUI packages, etc.

The crash

I started the update but forgot about it, promptly. My dad was semi-supervising it, since he was using the laptop on-and-off. I came back to it a couple of days later, and I ran an autoremove, assuming everything else in the install went ok. Everything continued to work alright until some time later, we had to restart the X server because it had hung up. And it never came back. And on a full restart, no network – both Ethernet and Wifi.

`chroot` to the rescue!

Thankfully these are not the days when I had access to a single computer, and crashing it meant running to a friend and using their computer to download stuff. I quickly made a bootable USB on my laptop.

I boot my dad’s laptop using the live distro and chroot to the installed OS using the live distro. Live Ubuntu has Ethernet working, thankfully.

For apt-get install and dist-upgrade to work correctly with the chroot, I had to mount a bunch of volumes.

Due to some network manager changes in the update, the chroot system still wasn’t connecting to the internet. I probably should’ve looked at the resolv.conf file first, but ended up going the offline package install route…

Offline updates

I generate a list of missing packages to be downloaded using the --print-uris flag to apt-get on the chroot system; And use wget to download the packages on the “live” system; Then copying these packages to /var/cache/apt/archives/ gets the update to finish.

But more missing packages!

I rebooted into the installed OS, once apt-get dist-upgrade seems to have everything resolved. But, I still didn’t have a network! I had to chroot again into the system, and this time I figured out that there was an issue with resolv.conf being a broken soft-link which seemed to cause the broken network (with Ethernet).

For WiFi, I had to install proprietary drivers for the Broadcom wireless card (BCM43142 802.11b/g/n).

I had to also install the ubuntu-desktop and related packages that seem to have gone missing, and on reboot everything was up and running!

Outro

When I told Shantanu, I didn’t have to reinstall my Ubuntu from scratch doesn’t mean that all my updates were flawless, and things never broke. I have had such broken updates a few times – network updates leaving the system in a broken state after network connections died, Ubuntu upgrade being in a borked state after the xz vulnerability was discovered, etc.

Updates do fail. But, more often than not I’ve been able to restore things thanks to dpkg ’s robustness and awesomness! And in some extreme cases, reaching for chroot to save myself.

There’s probably nothing new to learn or discover in this post, but just some help forum links that might come in handy, in future. In this age of AI answers, it seemed nice to look through some old forum QAs and work things out using them.

Thanks to Shantanu and Kamal for reading drafts of this post.

Let there be light, in skype!

Sat, 29 Mar 2014 00:00:00 +0530

At home, my video would always show a silhouette in G+ and Skype, and I always thought that this was because the lighting at home was not sufficient. At office, the video was decent. But, moving to sit right under the light also didn’t help much.

Struggling with a bunch of tools like v4lctl, guvcview didn’t help. But, during these struggles I noticed that cheese would show me bright and cheerful, while all the other programs showed my silhouette.

I set out to “fake” the output of cheese as a video device that skype and other programs could use. But, I didn’t have to go all the way. I ended up using v4l2loopback to create a loopback video device, and just using gst-launch to redirect video to that device, did the trick! Thanks gstreamer! Thanks v4l2loopback! :)

Here’s a convenient script to use it every time I need it.

numpy, pacman and me

Sun, 31 Jan 2010 00:00:00 +0530

I’m now officially a part of the Arch Linux community! Arch Linux is a lightweight and flexible Linux® distribution that tries to Keep It Simple.

I have started using arch from less than a week or so. It took me a while, not too long, to realize the beauty of this distro. I was trying to tweak the settings of my org-mode’s remember (on Karmic), trying to make it work the way I liked it. After breaking my head with .emacs and lisp for a while, I realized the version of my org-mode was way different from the version of the docs, I was reading. It didn’t take long to figure out, which version of org-mode to get. As a matter of curiosity, I checked AUR for the version, and true to Arch’s reputation it was bleeding edge! I was still using Karmic, since I hadn’t got my Arch installation working the way I like it, yet. Out of laziness. sudo reboot; to hell with laziness!

I was setting up things I regularly use, tweaking my way around. After a day or so, I find python-numpy is out of date. And to top it, an orphaned package! I didn’t feel one bit good about this. After some futile attempts to suppress my discomfort, I sat down to work.

After an afternoon of effort, I created my first PKGBUILD. :) I now have python-numpy installed using pacman! Pleasure to join the Arch User Community! Also, thanks to lifeeth and Lynus Vaz, for the sparks.

PS: I’m using Arch with Openbox. It’s neat! PPS: org-mode is really awesome! It’s a world in itself. life in plain text, truly!]