root@hostname:~# uname -a
Linux hostname 4.15.0-20-generic #21-Ubuntu SMP Tue Apr 24 06:16:15 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
root@hostname:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04 LTS
Release:        18.04
Codename:       bionic
root@hostname:~# apt-get update
Hit:1 http://jp.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 http://jp.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:3 http://jp.archive.ubuntu.com/ubuntu bionic-backports InRelease        
Hit:4 http://security.ubuntu.com/ubuntu bionic-security InRelease               
Reading package lists... Done
root@hostname:~# apt-get dist-upgrade 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
  linux-image-3.13.0-147-generic linux-image-extra-3.13.0-147-generic python-pycurl unattended-upgrades
Use 'apt autoremove' to remove them.
The following packages have been kept back:
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
root@hostname:~# do-release-upgrade -c
Checking for a new Ubuntu release
No new release found.