LWN.net Logo

I'm still confused...

I'm still confused...

Posted Dec 10, 2011 22:39 UTC (Sat) by james (subscriber, #1325)
In reply to: I'm still confused... by pr1268
Parent article: Distribution quote of the week

At the moment, the situation is:

  1. initrd mounts /
  2. initrd switches to /
  3. userspace in / looks in /usr before /usr is mounted
  4. BUG!

Under this proposal:

  1. initrd mounts /
  2. initrd mounts /usr
  3. initrd switches to /
  4. userspace in / looks in /usr
  5. the bug is hidden; /usr was mounted before "real" userspace ever got started.

So this means that you can have a separate /usr if you're prepared to have an initrd, or you can use your own kernels without initrds if you put /usr on the same filesystem as /.


(Log in to post comments)

I'm still confused...

Posted Dec 11, 2011 5:27 UTC (Sun) by raven667 (subscriber, #5198) [Link]

And I think this bears repeating, the first case where /usr is on a separate partition and stuff breaks during boot if it's not mounted is the _current_ case, not the case being introduced by the proposed change. There has been some effort over the previous years to audit the boot process and move binaries from /usr to / to fis this when the issue is detected but this has been scattershot and incomplete.

The proposal to just move everything to /usr and make sure it is always mounted directly after / _fixes_ this problem once and for all. The fact that this also fixes another set of thorny cases is just gravy, the fact that this has been successfully done on other big UNIX systems is a great endorsement. This doesnt have anything to do with systemd trying to eat your baby, It just exposed more pre-existing cases that were broken in the current setup.

I'm still confused...

Posted Dec 11, 2011 17:54 UTC (Sun) by jrn (subscriber, #64214) [Link]

> This doesnt have anything to do with systemd trying to eat your baby, It just exposed more pre-existing cases that were broken in the current setup

Did systemd actually provoke any worse behavior? I had assumed it was just warning about this class of bugs for kicks.

I'm still confused...

Posted Dec 12, 2011 4:08 UTC (Mon) by raven667 (subscriber, #5198) [Link]

Systemd starts services as needed which probably created several service start orders that, while perfectly valid, hadnt been tested in practice and broke.

Copyright © 2013, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds