Unfortunately no one can be told what fun_plug is - you have to see it for yourself.
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I am trying to use unionfs as root filesystem. The firmware ro, with an usbstick rw overlay. To do so I'm using reloaded.ko, and an initrd containing this /init script: (there's a symlink /linuxrc pointing to it)
#!/bin/sh
echo starting initrd/linuxrc...
mount -t proc /proc /proc
ROOT_RO=` cat /proc/cmdline | sed 's/.*root=// ; s/ .*//'`
ROOT_RW=` cat /proc/cmdline | sed 's/.*overlay=// ; s/ .*//'`
INIT=` cat /proc/cmdline | sed 's/.*init=// ; s/ .*//'`
echo mounting $ROOT_RO and $ROOT_RW
mount -o ro $ROOT_RO /mnt-ro
if [ $? -ne 0 ] ; then
echo could not mount $ROOT_RO. Starting shell....
/bin/sh
fi
mount -o rw -o noatime $ROOT_RW /mnt-rw
if [ $? -ne 0 ] ; then
echo could not mount $ROOT_RW. Starting shell....
/bin/sh
fi
insmod /lib/modules/unionfs.ko
mount -t unionfs -o dirs=/mnt-rw=rw:/mnt-ro=ro -o noatime unionfs /mnt
if [ $? -ne 0 ] ; then
echo could not mount unionfs. Starting shell....
/bin/sh
fi
echo unionfs mounted, moving mounts...
mkdir /mnt/mnt/ro
mount --move /mnt-ro /mnt/mnt/ro
mkdir /mnt/mnt/rw
mount --move /mnt-rw /mnt/mnt/rw
printf "0x%x%02x" ` mountpoint -d /mnt | sed 's/:/ /' ` > /proc/sys/kernel/real-root-dev
umount /proc
exec switch_root /mnt $INIT "$@" </dev/console >/dev/console 2>&1
echo Failed. Starting shell....
/bin/shThe serial output during and shortly after running initrd:
RAMDISK: squashfs filesystem found at block 0 RAMDISK: Loading 595KiB [1 disk] into ram disk... done. VFS: Mounted root (squashfs filesystem) readonly. starting initrd/linuxrc... mounting /dev/mtdblock1 and /dev/sdc1 kjournald starting. Commit interval 5 seconds EXT3-fs warning: maximal mount count reached, running e2fsck is recommended EXT3 FS on sdc1, internal journal EXT3-fs: recovery complete. EXT3-fs: mounted filesystem with ordered data mode. Registering unionfs 2.1.8 (for 2.6.18.8) unionfs mounted, moving mounts... #------------ Here switch_root is called ---------------- VFS: Mounted root (squashfs filesystem) readonly. Trying to move old root to /initrd ... /initrd does not exist. Ignored. Unmounting old root VFS: Busy inodes after unmount of sdc1. Self-destruct in 5 seconds. Have a nice day... Trying to free ramdisk memory ... okay Freeing init memory: 116K
When I exchange switch_root by chroot everything works. So the filesystem(s) is OK. Why is the root remounted again?
The commandline is
rootfstype=squashfs root=/dev/mtdblock1 ro mtdparts=physmap-flash.0:2432k(kernel),12928k(initrd),896k(etc),-(bootbase) console=ttyS0,115200n8 mem=128M init=/linuxrc rootdelay=10 overlay=/dev/sdc3 reloaded
$INIT expands to /linuxrc, which is a symlink to /bin/busybox in the firmware. I tried to change it to a symlink to /etc/init.d/rcS in the rw layer, but that didn't help either.
I have tried it with and without the 'real-root-dev' line. Doesn't change anything.
I have found that the pid of the script has to be 1, in order to execute switch_root. When I drop a shell, I can see that process 1 is [swapper]. Don't know what that is. When I force a different pid for the script, I get n error: 'switch_root: no rootfs', so I suppose [swapper] is the script, somehow.
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I thought maybe the root= parameter must point to the real rootdevice. So i tried to provide it. The mount command says:
unionfs on /mnt type unionfs (rw,dirs=/mnt-rw=rw:/mnt-ro=ro)
So I added root=unionfs to the commandline:
Root-NFS: No NFS server available, giving up. VFS: Unable to mount root fs via NFS, trying floppy. VFS: Cannot open root device "unionfs" or unknown-block(2,0) Please append a correct "root=" boot option Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
According to mountpoint the major:minor of this unionfs is 0:12. So I tried /dev/0:12. The same output (except the ´unionfs´ string). I tried without a root= parameter. The same output, only ´unionfs´ is exchanged by '<NULL>'.
Another fuzzy thing I found: reloading of this kernel only succeeds if I issue a /sbin/reboot. When I switch the box off and on, reloading stops:
reloaded for DNS-323, 2007 tp@fonz.de zImage: 1931380 bytes loaded 131072 of 1931380 bytes at c7ee0000 / 07ee0000 loaded 131072 of 1931380 bytes at c7f40000 / 07f40000 loaded 131072 of 1931380 bytes at c7f80000 / 07f80000 loaded 131072 of 1931380 bytes at c7fc0000 / 07fc0000 loaded 131072 of 1931380 bytes at c7800000 / 07800000 loaded 131072 of 1931380 bytes at c7840000 / 07840000 loaded 131072 of 1931380 bytes at c7880000 / 07880000 loaded 131072 of 1931380 bytes at c78c0000 / 078c0000 loaded 131072 of 1931380 bytes at c7900000 / 07900000 loaded 131072 of 1931380 bytes at c7940000 / 07940000 loaded 131072 of 1931380 bytes at c7980000 / 07980000 loaded 131072 of 1931380 bytes at c79c0000 / 079c0000 loaded 131072 of 1931380 bytes at c7a00000 / 07a00000 loaded 131072 of 1931380 bytes at c7a40000 / 07a40000 loaded 96372 of 1931380 bytes at c7a80000 / 07a80000 zImage: OK (15 segments) initrd: 610304 bytes loaded 131072 of 610304 bytes at c7aa0000 / 07aa0000 loaded 131072 of 610304 bytes at c7ae0000 / 07ae0000 loaded 131072 of 610304 bytes at c7b40000 / 07b40000 loaded 131072 of 610304 bytes at c7b60000 / 07b60000 loaded 86016 of 610304 bytes at c7ba0000 / 07ba0000 initrd: OK (5 segments) dns323_machtype = 859 CMDLINE: mtdparts=physmap-flash.0:2432k(kernel),12928k(initrd),896k(etc),-(bootbase) console=ttyS0,115200n8 mem=128M init=/linuxrc rootdelay=10 unionfs_ro=/dev/mtdblock1 unionfs_rw=/dev/sdc1 RLT MEM: start 00000000 size 128MB INITRD: start 00800000 size 610304 dns323_taglist = 7c2f000 (c7c2f000) copying 2160 bytes reboot code from bf0c11b8 to c7eba000 dns323_reboot_start = 7eba000 Reloading... Uncompressing Linux............................................................................................................................ done, booting the kernel.
Then it just stops. The box doesn't react on the powerbutton, which it does after a kernel panic.
Is there some flag which survives a reboot? When doing a soft reboot, the bootloader is involved, and I cannot see any difference between a hard boot and a soft one.
It seems that this is only a problem with kernels compiled with the codesourcery toolchain, not with the ZyXEL provided montevista toolchain.
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Are you really using an initrd? Or is it an initramfs (cpio archive)? I think you don't need a root= parameter at all. About the switch_root, I think it's common to cd to the new root directory, and use "switch_root . /sbin/init". I also think that you need a populated /dev in the new root tree, so /dev/console can be opened (this may be the reasons you log stops after 'Freeing init...').
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fonz wrote:
Are you really using an initrd? Or is it an initramfs (cpio archive)?
I create it with mksquashfs. Can I also provide a cpio archive to reloaded.ko? Will it automagically be treated as initramfs?
About the switch_root, I think it's common to cd to the new root directory, and use "switch_root . /sbin/init".
Ok, I'll try.
I also think that you need a populated /dev in the new root tree, so /dev/console can be opened (this may be the reasons you log stops after 'Freeing init...').
It doesn't stop there. It boots fine, it only (re)mounts the default root to /dev/mtdblock1.
Edit:
cd /mnt exec switch_root . /sbin/init
has the same behaviour as ´exec switch_root /mnt /linuxrc´. After this command the kernel will mount the device given in root=, or panic out when not provided.
Last edited by Mijzelf (2009-11-08 19:04:12)
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Mijzelf wrote:
I create it with mksquashfs. Can I also provide a cpio archive to reloaded.ko? Will it automagically be treated as initramfs?
Yes, of course. I've used an initramfs to boot armedslack ( http://www.inreto.de/dns323/armedslack/ramdisks/ ).
The busybox switch_root has a comment:
If you're _not_ running out of init_ramfs (if for example you're using initrd
instead), you probably shouldn't use switch_root because it's the wrong tool.
For initrds, they recommend pivot_root. But I think it's better to use an initramfs.
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Thanks, using an initramfs works. Pure magic. I think I'll have to do some reading about the difference of initrd and initramfs.
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