sshd command

 For communication and checking sshd service we can use sshd command.

Let me show how sshd command working:

1) what is sshd? 

sshd = ssh daemon 

When you need use sshd please use /usr/sbin/sshd -- use absolute path

- when you have error message: "sshd re-exec requires execution with an absolute path" - use the absolute path: 

you know how: 

a) whreis sshd

b) /usr/sbin/sshd

2) use 4 or 6 

#forces sshd to use ipv4 only

/usr/sbin/sshd -4 

#forces sshd to use ipv6 only

/usr/sbin/sshd -6 

3) checking sshd configuration file: 

/usr/sbin/sshd -t

-t is test for checking sshd configuration

4) show configuration file to output: 

/usr/sbin/sshd -T

5) when we need debug mode

/usr/sbin/sshd -d 

- of course we use 3 levels of debug 

/usr/sbin/sshd -d -d -d 

(it is similar like in command ssh (with -v or -vvv)

6) debug and error mode

/usr/sbin/sshd -d -e

- in some lines I have added text  and check via sshd...please check what is write in this picture