[우분투] The following packages have been kept back

>> 발생원인
패키지 업그레이드 진행시, 의존성이 변경되는 경우 및 신규 패키지를 설치해야하는 경우에 위 메시지 발생됨.

>> 발생과정
$ sudo apt-get update && sudo apt-get upgrade -y

The following packages have been kept back:
...


>> 해결방법
(1)
$ sudo apt-get --with-new-pkgs upgrade
...

(2)
$ sudo apt-get install aptitude -y
$ sudo aptitude safe-upgrade