take changes in file sshd_config file without server reboot
Simply restart the sshd service:
sudo service sshd restart
or:
sudo /etc/init.d/sshd restart
There's an even less intrusive way to do this, without restarting the SSH service.
From man sshd
:
sshd rereads its configuration file when it receives a hangup signal, SIGHUP, by executing itself with the name and options it was started with, e.g. /usr/sbin/sshd.
So you can use a command like the following to send SIGHUP to the SSH server process:
sudo kill -SIGHUP $(pgrep -f "sshd -D")
The pgrep -f "sshd -D"
part will return only the PID of the sshd daemon process that listens for new connections, since there are likely to be other PIDs for each active session that don't need the signal.
For Systemd Systems - Ubuntu default
sudo systemctl reload sshd.service
or
sudo systemctl reload sshd
or
sudo /bin/systemctl reload sshd.service
For Sysvinit / Systemd
sudo service sshd reload
or
sudo /etc/init.d/sshd reload
Ubuntu uses systemd: Here the service
command passes the units: start, stop, status, and reload through to their systemctl/initctl equivalents.