[LINUX] Ubuntu (18.04.3) SSH edition

1. Update
$sudo apt update

This is basically done every time.

2. Change root password
$ sudo passwd root

Set a password for root privileges.

It's a little scary, so set it longer.

I was able to log in to Root for the time being.

$ sudo su -

This will switch to the root prompt.

Add the following here with vi.


+ PermitRootLogin no

You can disable root login by restarting sshd.

$ systemctl restart ssh
$ failed to restart sshd.service unit sshd.service not found

Fa! ??

As I investigated, I had to install openssh-server in the first place.

$ sudo apt-get install openssh-server

Then, fix the following


- PermitRootLogin prohibit-password
+ PermitRootLogin no


$ sudo /etc/init.d/ssh restart

Yes ... (Can't you restart?).

When I looked it up, I had to start the sshd service.

$ sudo aptitude install ssh

Try entering from the Mac terminal.

$ ssh user@ip address

Oh, it's done.

Try to log in to root.

$ su root

If you can't log in with this, it's OK.

3. sshd port settings The following changes.


- # Port 22
+ Port 2022


$ sudo /etc/init.d/ssh restart

That's it.

4. Firewall port number closed → new port setting Check below.
$ sudo ufw status

22 that was released last time is deleted (it seems not so good)

$ sudo ufw delete allow 22

New port open

$ sudo ufw allow 2022
$ sudo ufw reload

2022 is now open

Confirm that you cannot enter with ↓.

$ssh account name@IP address

I couldn't enter without ↓.

$ ssh -p port number account name@IP address

Finally It started at 9 pm and it was such a time.

I will go to bed tomorrow.

Next time, I would like to connect using the public key authentication method.

(It doesn't stop when you start it)

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