/etc/init.d/udev-finish attempts to write to read-only root

Bug #224870 reported by Remi Broemeling on 2008-04-30
Affects Status Importance Assigned to Milestone
udev (Ubuntu)

Bug Description

Binary package hint: udev

In the /etc/init.d/udev-finish script it attempts to write to /etc/udev/rules.d, which will not work if the machine does not have write-access to that location (i.e. NFS RO-roots are a good example). Attached is a patch that naively fixes this by a simple -w check on /etc/udev/rules.d.

Remi Broemeling (remi-nexopia) wrote :

Note: I had to tweak the patch to make it work correctly using dash as the shell.

Specifically, in my case, `[ -w /etc/udev/rules.d ]` does not seem to work correctly using the dash built-ins, so I tweaked the conditional to give the full path to `[`, which bypasses the buggy built-in.


if /usr/bin/[ -w /etc/udev/rules.d ]; then

/usr may not be mounted at that point.

Why doesn't [ -w ... ] work in dash?

Actually, -w doesn't work at all since POSIX says it can return TRUE if the filesystem is read-only.

An alternate test for writability is required.

Remi Broemeling (remi-nexopia) wrote :

[ -w /etc/udev/rules.d ] returns FALSE in BASH for a RO root
[ -w /etc/udev/rules.d ] returns TRUE in DASH for a RO root
/usr/bin/[ -w /etc/udev/rules.d ] returns FALSE in BASH and DASH (and I assume every other shell) for a RO root

I had thought that POSIX specified that -w should return FALSE when used on a read-only filesystem, but perhaps I was incorrect.

A kludge would be to try and touch a file in /etc/udev/rules.d (errors to /dev/null), and then check the return code.

Changed in udev:
importance: Undecided → Low
status: New → Triaged
Changed in udev:
status: Triaged → Fix Committed
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package udev - 137-1

udev (137-1) jaunty; urgency=low

  * New upstream release:
    - udevadm test no longer has force option.
    - udevd has --resolve-names=early|late|never option.
    - Group of IDE CD-ROM drives fixed. LP: #315997.
    - Group of DRI subsystem fixed. LP: #317430.
    - /etc/udev/rules.d not existing is not an error. LP: #315780.
    - Bug where device nodes would be replaced by symlinks on rename has been
      fixed. LP: #315979.

  * Use --resolve-names=never in the installer and initramfs, since we don't
    have a useful name service. LP: #319199.
  * Since we don't have to worry about group lookup, we may as well copy the
    default rules into the initramfs as well. This actually double-solves
    LP: #315979.
  * Make sure the root filesystem is writable before attempting to copy
    generated rules across. LP: #224870.
  * Remove /dev/MAKEDEV symlink; the FHS no longer requires it when /dev
    is automatically managed.

  * It is not permitted to call udevadm trigger or settle during an upgrade
    without depending on udev. Attempting this will fail.
  * Change /etc/init.d/udev restart to actually restart the daemon, with a
    bit of detection to print a warning if we missed events while the
    daemon was down.
  * Refreshing /dev is now /etc/init.d/udev refresh-devices
  * Restart udev daemon after upgrade. LP: #317944.

 -- Scott James Remnant <email address hidden> Fri, 23 Jan 2009 15:15:07 +0000

Changed in udev:
status: Fix Committed → Fix Released
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