sshd can be configured optionally
with the aid of command line arguments which you specify when calling sshd (see "Starting and stopping sshd"),
with the aid of a configuration file.
The values specified as command line arguments have priority over the corresponding values in the configuration file.
Configuration file of sshd
By default sshd reads its configuration data from the /etc/ssh/sshd_config file. If you want to use a different configuration file, specify this with the parameter -f in the command line when you start sshd.
If a SIGHUP hangup signal is received, sshd reads the configuration file again and restarts. Here sshd is executed under the same name under which it was started, e.g. /opt/TCP-IP-SV/openssh/sbin/sshd.
In POSIX a restart will only be successful if no sshd session is currently active. (An active sshd session occupies the TCP/IP port and prevents the restart.)
Syntax of the configuration file
The configuration file of sshd must comply with the following syntax:
In each line the file contains a pair comprising keyword and associated argument or associated argument list:
For keywords no distinction is made between upper and lower case.
Arguments are case-sensitive.
Empty lines and lines beginning with “#” are interpreted as comments.
A detailed description of the configuration options is provided in the OpenSSH man pages.