10.4.4.1. Introduction
Most UNIX and Linux systems now run Secure SHell in order to leave out the
security risks that came with telnet. Most
Linux systems will run a version of OpenSSH, an Open Source implementation of the
SSH protocol, providing secure encrypted communications between
untrusted hosts over an untrusted network. In the standard setup X
connections are automatically forwarded, but arbitrary TCP/IP ports
may also be forwarded using a secure channel.
The ssh client connects and logs into the
specified host name. The user must provide his identity to the
remote machine as specified in the sshd_config file, which can usually be found in
/etc/ssh. The configuration file is
rather self-explanatory and by defaults enables most common
features. Should you need help, you can find it in the sshd man pages.
When the user's identity has been accepted by the server, the
server either executes the given command, or logs into the machine
and gives the user a normal shell on the remote machine. All
communication with the remote command or shell will be
automatically encrypted.
The session terminates when the command or shell on the remote
machine exits and all X11 and TCP/IP connections have been
closed.
When connecting to a host for the first time, using any of the
programs that are included in the SSH collection, you need to
establish the authenticity of that host and acknowledge that you
want to connect:
lenny ~> ssh blob
The authenticity of host 'blob (10.0.0.1)' can't be established.
RSA fingerprint is 18:30:50:46:ac:98:3c:93:1a:56:35:09:8d:97:e3:1d.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'blob,192.168.30.2' (RSA) to the list of
known hosts.
Last login: Sat Dec 28 13:29:19 2002 from octarine
This space for rent.
lenny is in ~
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It is important that you type "yes",
in three characters, not just "y". This
edits your ~/.ssh/known_hosts file, see
Section 10.4.4.3.
If you just want to check something on a remote machine and then
get your prompt back on the local host, you can give the commands
that you want to execute remotely as arguments to ssh:
lenny ~> ssh blob who
jenny@blob's password:
root tty2 Jul 24 07:19
lena tty3 Jul 23 22:24
lena 0: Jul 25 22:03
lenny ~> uname -n
magrat.example.com
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