Dreambox dm900/dm920 multiboot facility

[2stein]

in case of problems with multiboot on dm9xx the box is sometimes left in a non-bootable state. recovery involves reinstallation of a vix image or in some cases installation of a dreamos image before a vix image can be installed using rescue loader.
i found a simpler solution if you have the box hooked up to the pc using a usb cable and serial console.
when the box doesnt boot you boot into rescue loader, then enter the rescue loader command line interface in the serial console.
using the rescue loader command line interface lets you view/modify/reset the startup configuration.
for convenience i wrote a little script multi.sh.

here's a little demo:

root@dm900:~# # mount /data
root@dm900:~# mkdir /mnt/data
root@dm900:~# mount /dev/mmcblk0p3 /mnt/data
[  153.535569] EXT4-fs (mmcblk0p3): mounted filesystem with ordered data mode. Opts: (null)
root@dm900:~# ls -la /mnt/data
drwxr-xr-x   11 root     root          4096 May  4  2026 .
drwxr-xr-x    3 root     root             0 Dec  1 10:51 ..
drwxr-xr-x    3 root     root          4096 May  4  2026 TVC
drwxr-xr-x    2 root     root          4096 Dec  1 10:55 boot_backup
drwxr-xr-x   23 root     root          4096 Jan  1  1970 linuxrootfs1
drwxr-xr-x   16 root     root          4096 Apr 29  2026 linuxrootfs2
drwxr-xr-x   16 root     root          4096 May  1  2026 linuxrootfs3
drwxr-xr-x   16 root     root          4096 Mar 19  2026 linuxrootfs4
drwxr-xr-x   16 root     root          4096 May  1  2026 linuxrootfs5
-rw-r--r--    1 root     root           156 May  3  2026 log.txt
drwx------    2 root     root         16384 Oct 20  2016 lost+found
-rwxr-xr-x    1 root     root          8231 May  4  2026 multi.sh
drwxr-xr-x    2 root     root          4096 May  4  2026 picons
root@dm900:~# # use multi.sh
root@dm900:~# cd /mnt/data
root@dm900:/mnt/data# ./multi.sh
Dreambox DM900 Multi-Boot Recovery Tool v0.1.0

Usage: ./multi.sh <command> [args]

  mount                              Mount boot partition (/dev/mmcblk0boot1 -> /mnt/boot)
  umount                             Unmount boot partition
  list                               List all STARTUP* files with slot info
  active                             Show the current active boot config (STARTUP)
  activate <N>                       Set STARTUP = STARTUP_N  (switch active slot)
  set_slot <N> <rootsubdir> [root]   Write a new boot line into STARTUP_N
  reset                              Delete all STARTUP* files (reverts to default boot)
  backup                             Copy all STARTUP* files to ./boot_backup
  restore                            Restore STARTUP* files from ./boot_backup
  help                               Show this help

Examples:
  ./multi.sh mount
  ./multi.sh list
  ./multi.sh active
  ./multi.sh activate 2
  ./multi.sh set_slot 3 linuxrootfs3 /dev/mmcblk0p3
  ./multi.sh reset
  ./multi.sh umount
root@dm900:/mnt/data# #
# list startup config
root@dm900:/mnt/data# ./multi.sh mount
Mounted /dev/mmcblk0boot1 at /mnt/boot
root@dm900:/mnt/data# ./multi.sh list
File          Root device         Rootsubdir            Status
------------  ------------------  --------------------  -------
STARTUP       /dev/mmcblk0p2      linuxrootfs1          [active boot]
STARTUP_1     /dev/mmcblk0p2      linuxrootfs1          <-- matches active
STARTUP_2     /dev/mmcblk0p3      linuxrootfs2
STARTUP_3     /dev/mmcblk0p3      linuxrootfs3
STARTUP_4     /dev/mmcblk0p3      linuxrootfs4
STARTUP_5     /dev/mmcblk0p3      linuxrootfs5
STARTUP_6     /dev/mmcblk0p3      linuxrootfs6
root@dm900:/mnt/data# #
root@dm900:/mnt/data# ./multi.sh active
Active boot configuration (STARTUP):
kernel=/dev/mmcblk0p1 root=/dev/mmcblk0p2 rootsubdir=linuxrootfs1

the script goes into /data

 

[2stein]

looks like the max number of slots on a box is not limited by the space available for images but the 512 bytes size of the mmcblk0boot1 partition. the partition files on that partition have a size of 66 bytes each. so, the max number of slots is 6: Partition + Partition_1 ... Partition_6 = 462 bytes.