“SSH, the Secure Shell, is a set of protocols and software that
provide secure, remote terminal sessions between networked
computers. In addition to a simple remote command prompt, most SSH
implementations also provide secure forwarding of X Window traffic
as well as forwarding of connections to arbitrary TCP ports. These
features can protect otherwise insecure protocols such as POP,
IMAP, SMTP, and so on. An SSH session applies cryptographically
assured privacy and integrity protection as well as mutual
authentication to the data passing through it. Used properly, SSH
is an extremely valuable tool that helps users more safely navigate
today’s Internet and helps system administrators secure their
networks or perform remote administration.”
“1) I just installed OpenSSH, but password
authentication is not working!
Many modern flavors of Unix use “PAM” for password
authentication. PAM stands for Pluggable Authentication Modules. It
is an abstract framework for performing accounting, authentication,
and authorization (AAA). The idea is that programs can be written
to use PAM instead of particular AAA methods. The system
administrator can then customize AAA for different programs by
changing the host’s PAM setup. Existing services can use new AAA
methods, without change, simply by reconfiguring PAM or adding a
new PAM module to the system. For example, an IMAP server daemon
might log its actions to /var/log/imapd.log, and authenticate
clients via the Unix passwd map. If the daemon uses PAM for this,
the system administrator can direct that PAM instead log its
actions via syslog, and employ Kerberos for user authenticatation.
The IMAP server software need not have been written with explicit
support for either of these features, so long as it uses PAM.
…”
“2) I use particular combinations of SSH command-line
options all the time when connecting to various server hosts. Is
there a way to automate this, other than using shell-command
aliases?
Yes. Use labeled sections in the SSH client-configuration file.
For instance:
# ~/.ssh/config (SSH1 or OpenSSH)
Host foo.bar.com
User slade
PasswordAuthentication no
LocalForward 2143 localhost:143
With this bit of configuration, if you give the command ssh
foo.bar.com, SSH will behave as if you had instead typed:
ssh -l slade
-L 2143:localhost:143
-o PasswordAuthentication=no
foo.bar.com
Note that the labeled section is only used if the label matches the
hostname you give to SSH on the command line, verbatim.”