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Read-only boot flash drive?

Posted by hanker 
Read-only boot flash drive?
September 30, 2011 08:07AM
See the post below for more info...


Edited 2 time(s). Last edit at 10/18/2011 08:26AM by hanker.
Re: Read-only boot flash drive?
October 18, 2011 08:28AM
I have done some more research into making my rootfs usb flash drive read-only using the method described here:


This method entails adding a hook file to /etc/initramfs-tools/hooks, adding an init-bottom script to /etc/initramfs-tools/scripts/init-bottom, and rebuilding the initramfs.

I have done this on a test system: a Dell Mini 9 netbook (Intel Atom processor) with Debian squeeze, everything up-to-date. It boots from an ext3/linux swap hard disk, so basically the same setup as the Dockstar, just a hard disk instead of a flash drive. When I do the read-only procedure on that system and reboot, it works fine. The root filesystem is moved to an aufs filesystem: the boot drive is mounted read-only, but there is a writeable layer in RAM that gives the appearance of a writeable rootfs. All changes are lost on reboot though. Just what I want.

On this x86 test system, these lines appear in dmesg:

[    7.884717] aufs: module is from the staging directory, the quality is unknown, you have been warned.
[    7.897495] aufs 2-standalone.tree-32-20100125
[    7.898237] aufs test_add:248:exe[371]: uid/gid/perm /root.ro 0/0/0755, 0/0/01777

I also have a Dockstar that is set up the same: Debian squeeze, everything up-to-date. Here are the corresponding dmesg lines on the Dockstar:

[   12.960395] aufs: module is from the staging directory, the quality is unknown, you have been warned.
[   12.993986] aufs 2-standalone.tree-32-20100125
[   13.003956] aufs test_add:218:mount[124]: unsupported filesystem, /root.ro (rootfs)

So for some reason the same code that works fine on x86 Debian squeeze is producing an error in arm5 Debian squeeze.

Any ideas what may be going wrong here? Any directions for further research? Any help is appreciated! :)

Edited 1 time(s). Last edit at 10/18/2011 08:29AM by hanker.

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