SSH, The Secure Shell: The Definitive Guide, 2nd Edition

Problems and Solutions

In this section, we cover a wide range of difficulties, organized by category. The sidebar “The Top 10 SSH Questions” lists what, in our experience, are the most frequently asked of the frequently asked questions. We focus on problems that may occur in many versions of the SSH software on diverse operating systems. We don’t address the sorts of questions shown next that rapidly become obsolete.

• Compilation problems specific to one operating system, such as “HyperLinux beta 0.98 requires the --with-woozle flag”

• Problems and bugs that are specific to one version of SSH, particularly older versions

In all questions, we will assume you have already used debug or verbose mode (e.g., ssh -v) to isolate the problem. (If you haven’t, you should!)

12.2.1 General Problems

Q:	The commands ssh, scp, ssh-agent, ssh-keygen, etc., aren’t doing what I expect. Even the help messages look weird.
A:	Maybe they are Tectia programs when you are expecting OpenSSH, or vice versa. Try running these commands to find out: $ ssh -V $ ssh --help
Q:	When I try to connect to an SSH server, I get the error “Connection refused.”
A:	No SSH server is running where you tried to connect. Double-check the hostname and TCP port number: perhaps the server is running on a port different from the default?
Q:	When I log in, the message of the day (/etc/motd) prints twice.
A:	Both sshd and the login program are printing it. Disable sshd’s printing by setting the serverwide configuration keyword PrintMotd to no.
Q: ...