[LFS Trac] #2057: Udev-122

LFS Trac trac at linuxfromscratch.org
Thu May 22 20:55:16 PDT 2008

#2057: Udev-122
 Reporter:  matthew at linuxfromscratch.org  |        Owner:  lfs-book at linuxfromscratch.org
     Type:  enhancement                   |       Status:  new                          
 Priority:  normal                        |    Milestone:  7.0                          
Component:  Book                          |      Version:  SVN                          
 Severity:  normal                        |   Resolution:                               
 Keywords:                                |  
Comment (by alexander at linuxfromscratch.org):

 Replying to [comment:47 Bryan Kadzban]:
 > Since you're providing --subsystem on the udevadm command line, might
 this work with kernels that don't provide the subsystem symlink on their
 own (i.e. older than 2.6.18)?  It would be nice if it did (if you still
 have any of those kernels around to test).  :-)

 This does work on older kernels. As for --action=add, it is just the
 default and should be dropped to save space. So we have:

 for SYS in /sys/class/net/* ; do \
     INTERFACE=${SYS##*/} udevadm test --subsystem=net $SYS ; \

 plus a 2.6.18 kernel requirement for correct comments, and just 2.6.8 (or
 even below) for correct rules in the simplest case. Tested with the
 following kvm line:

 kvm -hda hda.dsk \
     -net nic,macaddr=50:54:00:12:34:56,model=ne2k_pci -net user \
     -net nic,macaddr=50:54:00:12:34:57,model=rtl8139 \
     -net nic,macaddr=50:54:00:12:34:58,model=pcnet \
     -net nic,macaddr=50:54:00:12:34:59,model=pcnet

 Since the SUBSYSTEMS keyword doesn't work with kernels below 2.6.18, the
 commands above, when applied to old kernels, create incorrect rules for
 the following two cases, neither of which are relevant to today's LFS:

  * Xen
  * S/390

 and, of course, in all cases where upstream udev doesn't create sensible
 rules with modern kernels.

Ticket URL: <http://wiki.linuxfromscratch.org/lfs/ticket/2057#comment:48>
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