First check your kernel version, so you won’t delete the in-use kernel image, running:
Now run this command for a list of installed kernels:
sudo dpkg --list 'linux-image*'
and delete the kernels you don’t want/need anymore by running this:
sudo apt-get remove linux-image-VERSION linux-image-VERSION
Replace VERSION with the version of the kernel you want to remove.
When you’re done removing the older kernels, you can run this to remove ever packages you won’t need anymore:
sudo apt-get autoremove
And finally you can run this to update grub kernel list:
Sometime for automation you need to be able to set the ubuntu hostname at boot ( or at network restart ) via DHCP / DNS .
To be able to do that you only have to add in /etc/dhcp/dhclient-exit-hooks.d a file named hostname with the following content:
if [ "$reason" != BOUND ] && [ "$reason" != RENEW ] \
&& [ "$reason" != REBIND ] && [ "$reason" != REBOOT ]
host=$(host $new_ip_address | cut -d ' ' -f 5)
echo $host > /etc/hostname
What it does ? Simple it hooks dhcpclient and after the client receives the new ip from dhcp it will make a simple reverse lookup for the ip received
and will set the hostname accordingly.