$ sudo do-release-upgrade
[sudo] password for nanumtip:
Checking for a new Ubuntu release
No new release found
새로운 배포판이 없다고 나옵니다.
$ sudo do-release-upgrade -d
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [198 B]
Get:2 Upgrade tool [1,147 kB]
Fetched 1,148 kB in 0s (0 B/s)
authenticate 'utopic.tar.gz' against 'utopic.tar.gz.gpg'
extracting 'utopic.tar.gz'