new software to make a read-only filesystem writeable

[od]

Could this be a useful tool for knoppix?

http://www.linuxdevices.com/news/NS5014525246.html

A Denx developer has released under the GPL a filesystem for embedded Linux systems that facilitates software updates of read-only filesystems. The "mini_fo" or mini fan-out filesystem works similarly to FreeBSD's union filesystem, according to developer Markus Klotzbücher, and serves "to virtually make a read-only filesystem writeable."
According to Klotzbücher, "The "mini_fo" filesystem was developed by extending a fistgen generated stackable filesystem to stack on top of two lower layers."
Klotzbücher developed mini_fo as a final thesis for his computer science degree, but, he says, "The code is stable and already actively used in a telecommunications project within Siemens."
Klotzbücher adds, "Not all features are implemented yet, but I plan to continue development. Any help is welcome!"
The mini_fo sourcecode is available in beta from Denx, along with Klotzbücher's 70-page thesis paper (PDF download).
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[Rootman]

A Denx developer has released under the GPL a filesystem for embedded Linux systems that facilitates software updates of read-only filesystems. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Correct me if I'm wrong but isn't this a fix for a problem that relly doesn't exist?

To make "most" RO file systems RW one only has to umount them and re mount them specifying rw. Knoppix mounts hard drives as RO by default.

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Visit my homepage: http://www.cox-internet.com/stevedavis/ - BORING! ;-}

[od]

Hi & thanks for the reply,

I'm a linux / knoppix newbie, so perhaps I goofed. I thought this may be a way of installing linux programs to the hard disk, that knoppix could detect and run as required, in a similar way to klik http://www.knoppix.net/forum/viewtopic.php?t=7680&postdays=0&postorder=asc&start=0.

I know knoppix is a readonly system and I'd love to be able to install and run my own programmes freely without having to install knoppix to the HD.

Is this an alternative or complementary method?

Hope this clarifies things

od

[probono]

Thanks for pointing out this kernel module! There exist others (e. g. transparency) which aim to do the same but so far they all had problems with the way Knoppix uses symbolic links.

I have donwloaded this one and did:



sudo su
unp mini_fo-0-5-9.tar.bz2
cd mini_fo
make
insmod ./mini_fo.o

The kernel module loaded successful, dmesg says "
Registering mini_fo version $Id: main.c,v 1.5 2004/04/02 14:42:53 wd Exp $". Wow. Now I tried to make /KNOPPIX/ writeable:


mkdir /tmp/mini_fo
mount -t mini_fo -o dir=/KNOPPIX/,dir2=/tmp/mini_fo/ /KNOPPIX/ /KNOPPIX/

Worked great! Now I can create subdirectories and files just where I want:


mkdir /usr/share/test
touch /usr/share/test/test.txt

Everything seems writeable, so why not try apt?



root@1[test]# apt-get update
Speicherzugriffsfehler


ooops! Something went wrong...
This is what dmesg says:


Unable to handle kernel NULL pointer dereference at virtual address 00000010
printing eip:
c8c99ff5
*pde = 00000000
Oops: 0000
mini_fo af_packet orinoco_cs orinoco hermes autofs4 reiserfs ext3 jbd ymfpci ac97_codec uart401 sound soundcore serial usb-uhci usbcore ds yenta_socket pcmcia_core apm rtc cloop
CPU: 0
EIP: 0010:[<c8c99ff5>] Tainted: P
EFLAGS: 00010282
eax: c16fd3e0 ebx: 00000000 ecx: c8ca0b24 edx: c8ca0cdf
esi: 00000000 edi: c5866f90 ebp: c5c03f3c esp: c5c03f14
ds: 0018 es: 0018 ss: 0018
Process apt-get (pid: 19789, stackpage=c5c03000)
Stack: 00000004 c8ca0b24 c8ca3aa0 c8ca0cdf c8ca0b0e 000002ea c5866f90 c5c03f68
c44be120 c5c03f78 00000000 c014fa6d c44be120 00000006 c5866f90 00000004
ffffffea bffff2d0 00000004 fffffff7 c5866f90 00000001 00000000 00000000
Call Trace: [<c8ca0b24>] [<c8ca3aa0>] [<c8ca0cdf>] [<c8ca0b0e>] [<c014fa6d>] [<c014b69a>] [<c014b84d>] [<c0108a67>]
Code: 8b 43 10 8b 50 34 85 d2 74 61 89 7c 24 08 b9 05 00 00 00 89
<1>Unable to handle kernel NULL pointer dereference at virtual address 00000010
printing eip:
c8c99ff5


Now I am stuck. What say the wizards here?

probono

[TyphoonMentat]

No idea :)

But how about http://ovlfs.sourceforge.net/ as well?

[garyng]

Thanks for pointing out this kernel module! There exist others (e. g. transparency) which aim to do the same but so far they all had problems with the way Knoppix uses symbolic links.


Really ? I thought they have made some process in this regard. I have done some modification to handle symbolic links issue back.