Bug#575204: initscripts: grep complains about invalid back reference in umountfs

[Dmitry Bogatov]

control: tags -1 +moreinfo

[2010-03-24 19:44] Sven Joachim <svenjoac at gmx.de>
> On 2010-03-24 13:57 +0100, Sven Joachim wrote:
> 
> > On 2010-03-24 10:15 +0100, Petter Reinholdtsen wrote:
> >
> >> [Sven Joachim]
> >>> Upon a reboot, I noticed grep complaining about an invalid back
> >>> reference.
> >>
> >> Interesting.  I did not show up when I tested it, so I suspect it is
> >> related to your setup.
> >
> > That's why I sent the contents of /proc/mounts.
> >
> >>> Running this script leads to a "grep: Invalid back reference" error
> >>> message here.  For the reference, these are the contents of
> >>> /proc/mounts:
> >> [...]
> >>> | /dev/disk/by-label/\134x2f / ext2 rw,relatime,errors=remount-ro,barrier=1,data=writeback 0 0
> >>
> >> This is the only one I can imagine lead grep to look for a
> >> back-reference (the \134 part).
> >>
> >> This sound a bit like the udev/mount incompatibility, where mount and
> >> udev encode special characters differently.
> >>
> >> Not quite sure how to fix it properly.  What kind of device is this?
> >
> > A normal hard disk partition, /dev/sda1.
> >
> > ,----
> > | % ls -l /dev/disk/by-label
> > | total 0
> > | lrwxrwxrwx 1 root root 10 Mar 24 13:12 \x2f -> ../../sda1
> > | lrwxrwxrwx 1 root root 10 Mar 24 13:12 \x2fhome -> ../../sda8
> > | lrwxrwxrwx 1 root root 10 Mar 24 13:12 \x2fusr -> ../../sda6
> > | lrwxrwxrwx 1 root root 10 Mar 24 13:12 \x2fusr\x2flocal -> ../../sda7
> > | lrwxrwxrwx 1 root root 10 Mar 24 13:12 \x2fvar -> ../../sda5
> > | lrwxrwxrwx 1 root root 10 Mar 24 13:12 swap -> ../../sda2
> > `----
> >
> >> How can I reproduce the setup leading to such strange device name?
> >
> > Create a label "/" for your root filesystem, e.g. with
> > "e2label /dev/root /", and reboot with "root=LABEL=/"
> > in the kernel commandline.
> 
> Just to confirm your conjecture: booting with "root=/dev/sda1" so that
> /proc/mounts does not have the strange /dev/disk/by-label/\134x2f entry
> makes the error go away.

Probably we could just pass -F option to grep? By the way, could someone
please explain what does this sed command mean?

	sed -n ':a;/^[^ ]* \/ /!{H;n;ba};{H;s/.*//;x;s/\n//;p}'