SSH: Basics¶
Overview¶
Secure Shell: secure login to remote computers
Unencrypted protocols, like
rsh,rlogin,telnet, …⟶ passwords readable on the wire
⟶ NSA must have it a bit harder!
⟶ SSH
Focus
SSH is a protocol (primarily, at least))
Main task: authentication and encryption
Main usage: remote login
Further usages
Copy data over the wire (
scp)File transfer (
sftp). Also usable as a network file system (⟶sshfs/FUSE)Port forwarding
Tunneling (a.k.a VPN)
…
Login¶
Logging in as user jfasch
$ ssh jfasch@home.com
Logging in under the same username as local
$ ssh home.com
Logging in and executing a remote command (using one’s login shell)
$ ssh jfasch@home.com ls -l
$ ssh jfasch@home.com 'ps -efl | grep sshd' # quoting necessary: '|' is a shell metacharacter
Exit Status, stdin, stdout: Scripting¶
Exit status of the remote command is propagated
$ ssh jfasch@home.com rm -f /etc/passwd
rm: unable to remove `/etc/passwd': Permission denied
$ echo $?
1
Standard Input, Output (und Error) are propageted, too
$ { echo hallo; echo hello; } | \
ssh jfasch@home.com cat | \
wc -l
Note
Only the middle part of the pipeline (
ssh cat) runs on the remote computerwc -lruns locally