Upgrade 9.04 to 9.10 headlessly

I did those steps from SSH (although not recommended).

1. apt-get update -> all repos updated
2. apt-get dist-upgrade -> somehow not necessary
3. do-dist-upgrade - the magic begins here
Respond to the questions according to the customizations you've done on your system.
In my case I've chosen to keep my locally installed versions.
At the end DO NOT REBOOT the system (do not answer Y at the final question).
4. Edit the /boot/grub/menu.lst and check if the serial console lines are still present. If not add them by hand before the beginning of "AUTOMAGIC KERNEL" section.
5. Now it would be safe to reboot... Good luck.

If you want to upgrade to grub2 (as I did) do the following:
1. apt-get install grub2
2. Edit the /etc/defaults/grub to something as:

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.

GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT="3"
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
#GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=serial

GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,38400n8"
GRUB_SERIAL_COMMAND="serial --speed=38400 --unit=0 --word=8 --parity=no --stop=1"

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true

# Uncomment to disable generation of recovery mode menu entrys
#GRUB_DISABLE_LINUX_RECOVERY="true"

The bolded lines are my modifications for the file.

3. Run /usr/sbin/update-grub as advised.