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--- change_root [2012/02/21 01:06] – typos excogitation
+++ change_root [2012/02/23 00:59] (current) – [How to recover a broken rootfs or an unbootable bootimg] armelf
@@ Line 1: / Line 1: @@
+====== How to recover a broken rootfs or an unbootable bootimg ======
+DRAFT
+Don't panic, there are solutions buried to go back on the right way, especially of if you have made [[backups|backups]] of your partitions.
+This methods are necessary until a true bootloader like [[uboot|u-boot]] or GRUB will be ported on the AC100.
+===== Chroot =====
 no idea if someone else finds this useful ... in case:
@@ Line 11: / Line 20: @@
  - Unmount the partition you want to chroot to:
-  <code>
+<code>
   sudo umount /media/<mointpoint of the desired partition>
-  </code>
+</code>
   e.g. sudo umount /media/6ca3f514-dc34-4230-a997-ebe156d108c0
  - mount that partition to /mnt:
-  <code>
+<code>
   sudo mount /dev/<desired partition (unmounted above)> /mnt
-  </code>
+</code>
-  e.g. sudo mount /dev/mmcblk0p7 /mnt
+  e.g. **sudo mount /dev/mmcblk0p7 /mnt** for rootfs installed in eMMC
  - mount additional stuff (dev/sys/proc):
-  <code>
+<code>
   sudo mount -o bind /dev /mnt/dev
   sudo mount -o bind /sys /mnt/sys
   sudo mount -t proc /proc /mnt/proc
-  </code>
+</code>
  - chroot
-  <code>
+<code>
   sudo chroot /mnt /bin/bash
-  </code>
+</code>
 You can now tweak your system. (e.g. you can install additional stuff from the repositories,
@@ Line 46: / Line 55: @@
 </code>
+==== Chroot from initramfs ====
+TODO based on initramfs of Ubuntu bootimg.
+===== Flash another kernel =====
+if for an unknow reason [[http://ac100.grandou.net/sosboot|SOSBOOT]] is unable to read your rootfs (for example NILFS2 or BTRFS filesystem) just after flashing a new kernel with a filesystem module which isn't loaded by **initrd**, you ended with an unbootable system and you are in chicken-egg trouble... One possible solution, is to [[kerneldev?&#Compilation environment consideration|rebuild a kernel]] with this filesystem type module builtin. Then backup your broken partition 6 image with [[putusb|putusb]] or [[nvflash|nvflash]]. Make a copy of this backup and use [[abootimg|abootimg]] to update it with this new kernel:
+<code>
+abootimg -u /tmp/copy-of-partition_6.img -k .../arch/arm/boot/zImage
+</code>
+and download it back to your AC100 with [[putusb|putusb]] or [[nvflash|nvflash]], then reboot and correct your rootfs or your bootimg according to make again bootable your AC100 with the last refinement.