203 lines
5.6 KiB
Markdown
203 lines
5.6 KiB
Markdown
---
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title: My experiences using runit in Arch Linux
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---
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In around 2012,
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after using busybox runit instead of sysvinit in my
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[Dirtbags Tiny Linux](https://woozle.org/neale/g.cgi/ctf/dbtl)
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distribution,
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I decided to try it out on my laptop, too.
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Here's how that went.
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My older paper on specifics of the conversion
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is still online: [Runit on Arch](arch-runit.html)
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Motivation
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==========
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I wanted to see if I could get a working system without having systemd
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installed at all.
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Not because I hate systemd,
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but because I love runit.
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I am acutely aware that a lot of people have strong opinions about systemd.
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Please: you don't need to share them with me.
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I don't care.
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Replacing init
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--------------
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First and most obvious was to get a getty running with my own
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`/sbin/init`.
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At the time,
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arch had just switched over to systemd,
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and had a recently-maintained systemv-init.
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Copying that,
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I was able to write a new init in Bourne shell.
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The resulting init did the following:
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* Mount and set up special filesystems (proc, sys, dev)
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* Set the system clock
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* Populate /dev (with `mdev -s`)
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* Load drivers (by reading `modalias` files in /sys)
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* Set the hostname
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* Bring up the loopback network interface
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* Set up cryptographic devices, if there are any
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* `fsck -A`
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* Remount / read-write
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* Mount everything else
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* Hand off to `runsvdir`
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Not bad, really.
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Setting up runit services
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-------------------------
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I won't go into this too much, it's well-documented elsewhere.
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At this point, I was able to get a getty going,
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but X11 wasn't recognizing the keyboard or mouse.
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Making X11 work
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---------------
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X11 at the time wanted `udev`,
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so I just ran that from init.
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But, a few months later,
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X was able to start without `udev`,
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so I took it out and figured out the keyboard and mouse problem.
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It had something to do with `evdev`;
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I think `udev` provided some sort of `evdev` help to X11,
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so I had to create some files in `/etc/X11/xorg.conf.d`
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to disable `AutoAddDevices`.
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Then the keyboard and mouse worked.
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I never looked into how to get evdev working again.
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Hot-plugging devices (like udev)
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--------------------------------
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For a while,
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you could echo something into a file under `/proc`
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and the kernel would run that for every uevent.
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You could set that program to `mdev` from busybox,
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and have a pretty well working system at that point.
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Newer kernels disabled support for this legacy interface.
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Now, you're supposed to monitor for Netlink events.
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But that's not too tough, it turns out.
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The kernel docs even have an example program to gather uevents.
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Wayland
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-------
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All you had to do was make a group with a certain name and add yourself to it.
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You also had to have write access to `/dev/dri/*` for the X11 stuff.
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Wayland was actually pretty low on crazy requirements.
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No consolekit or policykit or whatnottery needed.
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That's all?
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-----------
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Yup!
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Retrospective View
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==================
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After two years with this setup,
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I'm back to Ubuntu now,
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which means soon I'll have systemd.
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Looking back on it, here's how it went.
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It was blazing fast
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-------------------
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My new Ubuntu install boots a lot slower than my runit thing did.
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Maybe 2-3 times slower.
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Of course, it's doing way more.
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This is the cost of having a general-use distribution:
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you have to account for lots of cases,
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and need lots more support software.
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You can't rely on the machine owner to debug when,
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for instance,
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the console user doesn't have write access to the DRI device.
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It was easy (for me)
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--------------------
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Runit is really nice.
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I like it a lot.
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For old Unix beardos like me,
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having everything in Bourne shell is an attractive proposition.
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It required high wizardry
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-------------------------
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The head guy from the Archbang distribution tried to duplicate my work once,
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and failed to make everything work.
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We never did sort out what he needed to change.
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This was not something I'd recommend trying if you're not an expert
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and/or unwilling to debug a massively broken system for weeks.
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Stuff that never quite worked
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-----------------------------
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I had to set up a `dmix` device for ALSA,
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which usually worked,
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but sometimes things would get an exclusive lock on the sound hardware,
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which prevented other things from making sound.
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I could never get Chrome to get sound from the USB webcam I had to use at work.
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It would list it as a microphone source,
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and occasionally if I kept selecting every mic source over and over,
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it would start working.
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But it was never consistent,
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and I was never able to figure out why not.
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I never figured out how to get X11 to use evdev devices.
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Parting thoughts
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----------------
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Systemd fixes a lot of really ugly hacks.
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Things had become super kludgy,
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and systemd cleans it all up.
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I can't speak to systemd's architecture.
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It was annoying at times when stuff seemed to depend on systemd,
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but after looking into it,
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I was always able to find another way to do it.
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Bear in mind, I never tried to run Gnome or KDE.
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But I don't think people who want Gnome are going to want to futz around
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with writing run scripts for lid button events.
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The Linux kernel does not,
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to my mind,
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appear to be making any huge changes for systemd.
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Nothing I ran into here was out of reach for my project.
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Linux can still be used in a traditionally Unixy way.
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But you have got to bear in mind how un-Unixy things like X11 are.
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Wayland might be better, I don't know enough to say yet.
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My point is, Unix lost its roots decades ago with X11,
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or maybe even before with the Berkeley socket API,
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which didn't work from a shell script.
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I think it would be cool if somebody tried to make Linux
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look more like Plan9,
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and maybe the current backlash will kick that off.
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Runit is a way could do that.
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Please feel free to contact me :)
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