Попытка apt-get install sftp терпит неудачу: E: Пакет 'sftp' не имеет кандидата на установку

magnus@mt-dell:~$ sudo apt-get install sftp
[sudo] password for magnus: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package sftp is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'sftp' has no installation candidate

Что делать?