U-boot configuration for Debian upgrade

Before you can upgrade Debian from Debian 8 (jessie) to Debian 9 (stretch), you have to change a setting in the u-boot configuration. Unfortunately, the default settings no longer work with Debian 9 or 10. The new settings are compatible with Debian 8 (jessie), Debian 9 (stretch) and Debian 10 (buster), so you can make the changes at any time (before upgrading).

If you have serial console access to the mv2120, you can run some commands in u-boot. Simply interrupt the boot process by pressing a key and type the following:

setenv loadAddr 0x0600000
setenv bootcmd 'bootext2 0,1:1,2 0x0600000 /boot/uImage /dev/sda /dev/sdb'
saveenv

If you don't have a serial console, you can make the changes from within Debian. Run the following commands:

cat >/etc/fw_env.config <<EOF
/dev/mtd0           0x00000         0x1000     0x20000
EOF

fw_setenv loadAddr 0x0600000
fw_setenv bootcmd "bootext2 0,1:1,2 0x0600000 /boot/uImage /dev/sda /dev/sdb"

This creates a config file so the u-boot environment can be modified and uses fw_setenv to update two boot variables.

Once you made the changes, upgrades to Debian 9 should work fine and you can also use the Debian installer if you want to perform a new installation of Debian.