I used Putty to SSH into the phone (having got its IP address from my DHCP server logs) as root (using port 2222), and it worked. Now I wanted to use my public key, so I wouldn't be asked for the password again. Instructions were a bit fragmented, and I had a few false starts, but this is what I ended up doing:
- cd /data/dropbear
- mkdir .ssh
- chmod 700 .ssh
- cd .ssh
- echo 'my public key' >authorized_keys
- chmod 644 authorized_keys
- cd ..
- mount -o rw,remount -t yaffs2 /dev/block/mtdblock1 /system
- edit /system/bin/dropbear.sh to add
to the end of the command line.
- mount -o ro,remount -t yaffs2 /dev/block/mtdblock1 /system
- reboot the phone (type "reboot" at the command line, or use the Quick Boot app on the phone).
The mount commands switch the filesystem from read-only (its usual state) to read-write and back again.
Brilliant - I now have password-free root access to my phone using ssh from my PC (which has a real keyboard). Some experimentation shows I have most of the commonly-used Linux commands available to me.