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
Que faire?
Je pense que le paquet que vous voulez installer est openssh-server.
Sudo apt-get install openssh-server
Source: Comment installer un serveur SFTP restreint sur Ubuntu?