Problem:
A system does not boot and seems to freeze at bootsplash.
Solution:
It is possbile to edit the boot options for the UCS system within GRUB. You can disable the splashscreen and raise the loglevel - by that you can see what happens when the system freezes:
1. Press button "e" in GRUB bootloader
2. Find the follwing line:
linux ... /vmlinuz-... ... ro quiet loglevel=0 rootdelay=5 splash3. Edit the line: Remove "quiet" and change "slpash" to "nosplash" - also set "loglevel" to 5
the line should now look like this:
linux ... /vmlinuz-... ... ro loglevel=5 nosplash4. Boot by pressing F10
These changes are temporaliy and are re-set at next boot. You can make that change permanent by booting into the working UCS system, logging in as root, and setting the following UCR variables:
ucr set grub/bootsplash=nosplash grub/quiet=no grub/loglevel=5
Advanced options:
The default text console only has 80 columns and 25 rows, so some important output might scroll of. You can configure a serial console to capture that output.
Note 1: Many USB serial converters don't work reliably.
Note 2: Many high-end servers support serial console re-direction over network, for example over IPMI.
# Re-direct GRUB input/output to serial console:
cat >>/etc/univention/templates/files/etc/default/grub <<__GRUB__
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1"
__GRUB__
ucr commit /etc/default/grub
# Optional: Re-direct Linux kernel input/output to serial console:
ucr set grub/append='console=tty0 console=ttyS0,115200,8,N,1'
# This makes the serial console the default console (/dev/console), as ttyS0 is given last.
# By moving console=tty0 to the end, the VGA console will remain the main console.
# Optional: Start a login getty on the serial console:
sed -i -re '/^#?T0:/s/#//' /etc/inittab