Udev's secret remounting of /dev at /dev/.static/dev gives me pause.
How IS that done, anyway?

I am interested in using find and cpio to make a root filesystem
backup. How should I handle the /dev tree? If I just grab the
run-time /dev it will become the boot-time /dev of my restored
system. I don't understand if this has any ramifications or what
they are.

I can back up my root by booting into another linux, but that is
inconvenient.

It seems that I could just set udev_root to something like "/udev"
in /etc/udev.conf and that would work. That doesn't appeal because
of decades of finger memory for "/dev".

Thanks.

Be well,
Rob


Script started on Fri Feb 23 22:04:38 2007

vaph:/# uname -a
Linux vaph.private 2.6.8-2-686-smp #1 SMP Thu May 19 17:27:55 JST 2005 i686 GNU/Linux


vaph:/# cd /dev/.static


vaph:/dev/.static# find . -print
..
../dev
../dev/hdd
../dev/mem
../dev/hdd1
../dev/kmem
../dev/hdd2
../dev/null
../dev/hdd3
../dev/port
../dev/hdd4
../dev/zero

[ deletia ]

../dev/log
../dev/apm_bios
../dev/raw1394


vaph:/dev/.static# find . -xdev -print
..
../dev


vaph:/dev/.static# mount ############ no /dev/.static/dev listed
/dev/sda3 on / type ext3 (rw,errors=remount-ro)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
usbfs on /proc/bus/usb type usbfs (rw)
/dev/sda9 on /usr type ext3 (rw,noatime)
/dev/sda6 on /var type ext3 (rw,noatime)
/dev/sda7 on /tmp type ext3 (rw,noatime)
/dev/sda10 on /home type ext3 (rw,noatime)
/dev/sda12 on /priv type ext3 (rw,noatime)
/dev/sda13 on /pub type ext3 (rw,noatime)
tmpfs on /dev type tmpfs (rw,size=10M,mode=0755)
/dev/sdb3 on /mnt type ext3 (rw)


vaph:/dev/.static# exit
exit

Script done on Fri Feb 23 22:05:18 2007


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Just make sure you have the (empty) directories /dev and /dev/pts. The system DOES need a few devices before udev does its magic - for those create the device nodes the usual way. (have a look at the makedevices script for clues) I remember reading instructions on this months ago but can't recall the link - google will probably dig it up for you.



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On Sat, Feb 24, 2007 at 09:59:35AM +0100, pinniped wrote:
>
> Just make sure you have the (empty) directories /dev and /dev/pts. The
> system DOES need a few devices before udev does its magic - for those
> create the device nodes the usual way. (have a look at the makedevices
> script for clues) I remember reading instructions on this months ago but
> can't recall the link - google will probably dig it up for you.

MAKEDEV is not going to . I am trying to backup a system. If the
backup is not bootable, MAKEDEV is not usable. Aside from that, the
idea is to save the devices that are there; it is possible that some
package or person could add a special node. If that happens, a backup
should catch it.

The hiding of a mounted filesystem seems very broken to my sysadmin
side.

Be well,
rir


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> On Sat, Feb 24, 2007 at 09:59:35AM +0100, pinniped wrote:
> > Just make sure you have the (empty) directories /dev and /dev/pts. The
> > system DOES need a few devices before udev does its magic - for those
> > create the device nodes the usual way. (have a look at the makedevices
> > script for clues) I remember reading instructions on this months ago but
> > can't recall the link - google will probably dig it up for you.

On 24.02.07 16:52, rir wrote:
> MAKEDEV is not going to . I am trying to backup a system. If the
> backup is not bootable, MAKEDEV is not usable. Aside from that, the
> idea is to save the devices that are there; it is possible that some
> package or person could add a special node. If that happens, a backup
> should catch it.
>
> The hiding of a mounted filesystem seems very broken to my sysadmin
> side.

backup using dump/restore - it backs up whole filesystem (unless you
exclude/include only some files), even the "hidden" part.

however, udev remounts the original /dev to /dev/.static, with a small
hacks, you can mount that too.
--
Matus UHLAR - fantomas, uhlar@fantomas.sk ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
He who laughs last thinks slowest.


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On Sun, Feb 25, 2007 at 04:36:56PM +0100, Matus UHLAR - fantomas wrote:

> backup using dump/restore - it backs up whole filesystem (unless you
> exclude/include only some files), even the "hidden" part.

> however, udev remounts the original /dev to /dev/.static, with a small
> hacks, you can mount that too.

My question is what should I be backing up regarding udev?
You imply that, on a running system, /dev/.static/dev should be backed
up as /dev.

I don't have a problem with how to do this; I'll archive the dev stuff
along with other meta-data and stick it at the head of my archive, like:

cd /dev/.static && \
find ./dev -xdev -depth -print \
| $CPIO > $TMPDIR/dev.cpio

cd / && \
find ./$TMPDIR/README ./$TMPDIR/ARCHIVE_DATE ./$TMPDIR / \
-xdev -depth -print \
| $CPIO | $MEDIA_WRITER

Dump/restore is slick but I see it as only good for supporting a system.
I like my backups to also be suitable for use as a information archive.
I've settled on cpio archives for portability. It is bad enough trying to
find a working 5-1/4 drive or a 60meg 1/4 inch tape drive, without trying
to find an operating system that has a filesystem and version of restore that
match some 15 year-old archive.

Thanks for the reply; I didn't realize that about dump.

Be well,
rir


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rir wrote:
> On Sun, Feb 25, 2007 at 04:36:56PM +0100, Matus UHLAR - fantomas wrote:
>
>> backup using dump/restore - it backs up whole filesystem (unless you
>> exclude/include only some files), even the "hidden" part.
>
>> however, udev remounts the original /dev to /dev/.static, with a small
>> hacks, you can mount that too.
>
> My question is what should I be backing up regarding udev?
> You imply that, on a running system, /dev/.static/dev should be backed
> up as /dev.
>
> I don't have a problem with how to do this; I'll archive the dev stuff
> along with other meta-data and stick it at the head of my archive, like:
>
> cd /dev/.static && \
> find ./dev -xdev -depth -print \
> | $CPIO > $TMPDIR/dev.cpio
>
> cd / && \
> find ./$TMPDIR/README ./$TMPDIR/ARCHIVE_DATE ./$TMPDIR / \
> -xdev -depth -print \
> | $CPIO | $MEDIA_WRITER
>
> Dump/restore is slick but I see it as only good for supporting a system.
> I like my backups to also be suitable for use as a information archive.
> I've settled on cpio archives for portability. It is bad enough trying to
> find a working 5-1/4 drive or a 60meg 1/4 inch tape drive, without trying
> to find an operating system that has a filesystem and version of restore that
> match some 15 year-old archive.
>
> Thanks for the reply; I didn't realize that about dump.
>
> Be well,
> rir
>
>

I can't add anything to the discussion re. /dev, but am curious about
your reference to "a working 5-1/4 drive or a 60meg 1/4 inch tape drive,".

Since most hard disks are now less than 5-1/4 inches, are you referring
to floppy disks? And that tape size is ancient, I think.

If you have access to either a CD or DVD burner, you might want to look
into cdbackup/cdrestore (package name is cdbackup, IIRC). From the man
page:

DESCRIPTION
cdbackup is a utility to make streaming backups to
CD-R(W)/DVD-R(W) disks. It’s designed to work with any backup
tool which writes the backup to stdout (like tar/cpio/afio).

Bob

On Mon, Feb 26, 2007 at 08:56:32AM -0800, Bob McGowan wrote:
> rir wrote:
> >My question is what should I be backing up regarding udev?
> >You imply that, on a running system, /dev/.static/dev should be backed
> >up as /dev.

> I can't add anything to the discussion re. /dev, but am curious about
> your reference to "a working 5-1/4 drive or a 60meg 1/4 inch tape drive,".
>
> Since most hard disks are now less than 5-1/4 inches, are you referring
> to floppy disks? And that tape size is ancient, I think.

You are right. I have had rare occasion to look for stuff that is on
10 and 15 year old backups from my home systems.

> If you have access to either a CD or DVD burner, you might want to look
> into cdbackup/cdrestore (package name is cdbackup, IIRC). From the man

I do use CD- and DVD-RWs for backups these days. So far, I have most
of my partitions at under 3.5 gigs and so don't have to chunk things to
fit on DVDs. Well, I do have /pub and /priv filesystems that are large,
but these are pretty static and mostly replaceable. I suspect I'll move
to blue-ray discs within a few years before I feel a need for a chunker
like cdbackup, but I'm am glad to have the reference.

My comment about 60-meg QIC tapes was forward looking; I imagine that in
15 years I'll have the same problems with CDs.

Be well,
rir


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