Debian on embedded systems

Marcus Osdoba | 18 Jan 2011 23:11

HOWTO example for ReadOnly Rootfs using multistrap

Hello mailinglist,

I tried several embedded linux systems for my target device (seagate 
dockstar - 128MiB/kirkwood/4USBports) and finally came back to 
Debian/Emdebian.

Since I like to install the system onto the internal NAND flash,
my main requirement was to use a READ ONLY root file system -
or at least one without write access besides configuration issues.

The obviously volatile result was made public here:
http://gitorious.org/dockstar/emdebian-multistrap

The information is placed here, if anyone digging through the 
mailinglist archive would look for an example for
a) using multistrap
b) read only rootfs

The solution is not perfect but works for me. Makefiles would be
a better way than bash skripts, but at the beginning I wasn't aware
of the recipe/make character.

The skript set produces a ubi-image, ext2 image and tar.gz of the
generated rootfs. The way how this is created is ugly and
not very generic:
- no (marginal) sanity checks
- defining packages in conf file
- running multistrap
- tweak configuration (e.g. nameserver and iface)
- tweaking some packages for read only usage (e.g. fsck.ubifs, samba)

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Hector Oron | 18 Jan 2011 23:45

Re: HOWTO example for ReadOnly Rootfs using multistrap

Hello Marcus,

2011/1/18 Marcus Osdoba <marcus.osdoba <at> googlemail.com>:

> The obviously volatile result was made public here:
> http://gitorious.org/dockstar/emdebian-multistrap

Surely something to look at it. Thanks.

> I have found some bugs which could be filed against the BTS
> (excerpt of TODO:
> - fsck.ubifs dummy package similar to fsck.nfs (fsck.ubifs is not
> implemented)

>From UBI documentation:
UBIFS is tolerant of unclean reboots and power-cuts. It does not need
stuff like fsck.ext2.

> - noauth must be true even if Emdebian archive keyring installed on host
> system

I thought that was already fixed.

> - mksquashfs 4.0 from Squeeze did not work for me on my arm target, 4.1 from
> Sid does)

In which way failed for you?

> I don't know, if you appreciate information like this mail,

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Marcus Osdoba | 23 Jan 2011 12:03

Re: HOWTO example for ReadOnly Rootfs using multistrap

Am 18.01.2011 23:45, schrieb Hector Oron:
>
> Surely something to look at it. Thanks.
Hi Hector, many thanks for the feedback.

>
>> I have found some bugs which could be filed against the BTS
>> (excerpt of TODO:
>> - fsck.ubifs dummy package similar to fsck.nfs (fsck.ubifs is not
>> implemented)
>
>  From UBI documentation:
> UBIFS is tolerant of unclean reboots and power-cuts. It does not need
> stuff like fsck.ext2.
Yes. I know. That is what I found, too. But anyway the debian standard 
setup tries to check every filesystem (but nfs). Since there is no 
fsck.ubifs this produces alienate messages on startup. Debian ignores 
fsck for NFS - so it should ignore ubifs, too. The fsck.nfs thing was 
solved with a dummy package. To keep the pattern, a similar dummy 
package for fsck.ubifs should be created.
This bug ticket patches some skript:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=571241
Anyway, I prefere to keep the pattern and create a dummy package similar 
to fsck.nfs.

>> - noauth must be true even if Emdebian archive keyring installed on host
>> system
>
> I thought that was already fixed.
I did not try the newest version from sid. My host system is a debian

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Neil Williams | 19 Jan 2011 09:14

Re: HOWTO example for ReadOnly Rootfs using multistrap

On Tue, 18 Jan 2011 23:11:06 +0100
Marcus Osdoba <marcus.osdoba <at> googlemail.com> wrote:

> - noauth must be true even if Emdebian archive keyring installed on
> host system

Use multistrap from experimental - apt behaviour has changed during the
release cycle, again.

> I don't know, if you appreciate information like this mail,

Yes, all extra documentation is welcome. (If there are things on the
current website which need updating, put some alternative content on
the Wiki and I'll update from there.)

> so please don't bite me. Since I heavily used multistrap and
> Emdebian, I thought it would be worth to share the result with others.

Please add a link or other content to the Multistrap Wiki:
http://wiki.debian.org/Multistrap

Also, let me know if you have example configuration files to add to:
http://www.emdebian.org/multistrap/examples.php

--

-- 

Neil Williams
=============
http://www.linux.codehelp.co.uk/

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