Ubuntu update時に「Could not get lock /var/lib/apt/lists/lock. It is held by process」が発生

[kumamoto ~]$ sudo apt update
[sudo] kumamoto のパスワード: 
パッケージリストを読み込んでいます... 完了
E: Could not get lock /var/lib/apt/lists/lock. It is held by process 2151 (packagekitd)
N: Be aware that removing the lock file is not a solution and may break your system.
E: ディレクトリ /var/lib/apt/lists/ をロックできません