Upgrade the ubuntu non-long-term support version (applicable to ssh logon)

Upgrade the ubuntu non-long-term support version (applicable to ssh logon)

(1) The current system is not a long-term supported version and has been deprecated. It can only be upgraded by version.
Take the current system version 11.10 As An Example
Modify source. list to update the source to the general old source because the original source is unavailable.
Deb http://old-releases.ubuntu.com/ubuntu/ oneiric main restricted
The deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric main restricted
Replace oneiric with the current system version Code. The Code can be viewed using the lsb_release-a command.
Apt-get update
Apt-get install update-manager-core
Do-release-upgrade
You can upgrade to version 12.04 next to it.

Tips: If the version has not been deprecated, you can skip the step of modifying source. list.

(2) The current system is a long-term supported version and has not been deprecated. You can directly go from 10.04 --> 12.04 --> 14.04 ...... Upgrade between long-term supported versions
Take upgrading from 12.04 to 14.04 as an Example
Set source. in the list, replace the source with the domestic source of the 14.04 version, for example, 163, or you may feel that your source is already fast enough. in the list, change version code 12.04 to version code trusty of 14.04.
Apt-get update

Apt-get dist-upgrade

In other cases, please use the above two methods as the basis for flexible operations