Configure the /etc/ssh2/ssh2_config file

Securing and Optimizing Linux: RedHat Edition -A Hands on Guide
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# 16.3. Configure the `/etc/ssh2/ssh2_config` file

The configuration file for ssh2 `/etc/ssh2/ssh2_config` allows you to set options that modify the operation of the client programs. The files contain keyword-value pairs, one per line, with keywords being case insensitive. Here are the more important keywords; a complete listing is available in the man page for ssh2(1).

Edit the `ssh2_config` file, vi `/etc/ssh2/ssh2_config` and add or change, if necessary:

             # ssh2_config
             # SSH 2.0 Client Configuration File

             *:Port                            	22
             Ciphers                         	blowfish
             Compression                     	yes
             IdentityFile                    	identification
             AuthorizationFile               	authorization
             RandomSeedFile		                random_seed
             VerboseMode                     	no
             ForwardAgent                    	no
             ForwardX11                      	no
             PasswordPrompt		                "%U's password: "
             Ssh1Compatibility               	no
             Ssh1AgentCompatibility	                none
             NoDelay                         	yes
             KeepAlive                       	yes
             QuietMode                       	no

This tells ssh2_config file to set itself up for this particular configuration setup with:

`Port 22`

  The option `Port` specifies on which port number ssh connects to on the remote host. The default port is 22.

`Ciphers blowfish`

  The option `Ciphers` specifies what cipher should be used for encrypting sessions. The blowfish uses 64-bit blocks and keys of up to 448 bits.

`Compression yes`

  The option `Compression` specifies whether to use compression during sessions. Compression will improve communication speed and files transfers.

`IdentityFile identification`

  The option `IdentityFile` specifies an alternate name for the user's identification file.

`AuthorizationFile authorization`

  The option `AuthorizationFile` specifies an alternate name for the user's authorization file.

`RandomSeedFile random_seed`

  The option `RandomSeedFile` specifies an alternate name for the user's random seed file.

`VerboseMode no`

  The option `VerboseMode` instructs ssh2 to print debugging messages about its progress. This option is helpful in debugging connection, authentication, and configuration problems.

`ForwardAgent no`

  The option `ForwardAgent` specifies which connection authentication agent if any should be forwarded to the remote machine.

`ForwardX11 no`

  The option `ForwardX11` is for people that use the `Xwindow` GUI and want to automatically redirect `X11` sessions to the remote machine. Since we've set up a server and do not have a GUI installed on it, we can safely turn this option off.

`PasswordPrompt "%U's password: "`

  The option `PasswordPrompt` specifies the password prompt that will be displayed for the user when connecting to a host. Variables `%`U and `%`H give the user's login name and host, respectively.

`Ssh1Compatibility no`

  The option `Ssh1Compatibility` specifies whether or not to use SSH1 compatibility code with SSH2 for ssh1 users.

`Ssh1AgentCompatibility none`

  The option `Ssh1AgentCompatibility` specifies whether or not to also forward SSH1 agent connections with SSH2 for ssh1 users.

`NoDelay yes`

  The option `NoDelay` specifies if the socket option `TCP_NODELAY` should be enabled. It is recommended that you set this option to `yes` to improve network performance.

`KeepAlive yes`

  The option `KeepAlive` specifies whether the system should send keep alive messages to the remote server. If set to `yes` then the death of the connection or crash of remote machines will be properly noticed.

`QuietMode no`

  The option `QuietMode` specifies whether the system runs in quiet mode. This option must be set to `no` because in quiet mode, nothing is logged in the system log except for fatal errors. Since we want to have information about users sessions it is preferable to disable this option.

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