You can use command line to upgrade Ubuntu desktop or a headless server. Speaking of servers, it is recommended that you upgrade Ubuntu on a test server before doing it on a production server.
If you use SSH to log into your Ubuntu server, it’s a good idea to keep your OpenSSH session alive by adding the following line in /etc/ssh/sshd_config file on your server.
nano /etc/ssh/sshd_config
ClientAliveInterval 60
Save and close the file. Then restart SSH daemon.
systemctl restart ssh
To upgrade to Ubuntu 18.04, first run the following command to upgrade existing software.
apt update && apt dist-upgrade
Then make sure you have update-manager-core package installed.
apt install update-manager-core
After that, run the following command to begin the upgrade process.
do-release-upgrade
Then follow the on-screen instruction to upgrade to Ubuntu 18.04. Once the upgrade is finished, reboot your Ubuntu desktop or server. To check your Ubuntu version, run:
lsb_release -a
Output:
No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 18.04 LTS Release: 18.04 Codename: bionic
You also need to re-enable third-party repositories such as PPA because they are disabled during upgrade.
Attention: this update will not work on dedikuoti.lt OpenVZ servers except KVM servers.
OpenVZ container will return this message:
This version of the GNU libc requires kernel version 3.2 or later. Please upgrade your kernel before installing glibc.