Ubuntu 16.04 LTS (Xenial Xerus) released

Posted Apr 25, 2016 5:17 UTC (Mon) by zlynx (guest, #2285)
In reply to: Ubuntu 16.04 LTS (Xenial Xerus) released by linuxrocks123
Parent article: Ubuntu 16.04 LTS (Xenial Xerus) released

> If anything, SystemD mounting that filesystem without being asked is a bug, even ignoring the "destroy the machine" thing, because /you're not supposed to mount things without being asked to in fstab/!

You might want to tell that to the startup program that runs from inside initrd then. Those often mount /proc, /dev, /sys, etc. also, so that they can assemble the root filesystem. Probably efivars too because you might need to read a boot parameter. And of course the initrd software doesn't read /etc/fstab because the file doesn't exist yet.

Ubuntu 16.04 LTS (Xenial Xerus) released

Posted Apr 25, 2016 23:08 UTC (Mon) by linuxrocks123 (subscriber, #34648) [Link]

Yeah, some initramfs scripts can do some funky things. When I code an initramfs, my philosophy is, if you mounted /proc or /sys because you had to for some reason, you unmount them before switch_root. But not everyone follows that, and it works because everyone kind-of expects /proc and /sys and devtmpfs to sometimes be mounted by random crap -- or, more accurately, no one notices when they are, because they get mounted very quickly anyway. That's sloppy, though, and it's best if we don't add more pseudo-fses to the slop.

Also, btw, initrd has been deprecated for about a decade.

Ubuntu 16.04 LTS (Xenial Xerus) released

Posted Apr 25, 2016 23:24 UTC (Mon) by linuxrocks123 (subscriber, #34648) [Link] (1 responses)

Oh, also: why would you need efivarfs mounted to read a kernel parameter? Wouldn't that be in /proc/cmdline?

Ubuntu 16.04 LTS (Xenial Xerus) released

Posted Apr 25, 2016 23:40 UTC (Mon) by zlynx (guest, #2285) [Link]

Initrd, initramfs, potato, potahto.

I was thinking of the case where UEFI is booting an EFI enabled Linux kernel directly without an intermediate bootloader. In that case one way to pass data to the initramfs image is through EFI variables.

You can of course rewrite the boot entry to set the kernel command line but it seems safer to use other variables to reduce the risk of becoming unbootable.