ssh disable warning messages – Linux/Ubuntu

To disable ssh warning message we need to add LogLevel to quiet in $HOME/.ssh/config file.

LogLevel=quiet

We can also diable warning messages with ssh command as shown below:

$ ssh -o LogLevel=quiet 192.168.1.10

With following example we can also disable Host Key Checking, set known hosts file to null and disable logging:

$ ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o LogLevel=quiet 192.168.1.20

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ssh remove offending key – Linux/Ubuntu

 

ssh-keygen command is used to remove offending key entries from .ssh/known_hosts

Syntax to remove offending key of a host:

$ ssh-keygen -R hostName/IP_Address

Example 1:

$ ssh-keygen -R test.example.com

Above example will remove ssh key associated with hostname test.example.com

Example 2:

$ ssh-keygen -R 192.168.1.10

This example will remove ssh key associated with IP Address 192.168.1.10

Enable/Disable ssh access to root

Its always better to disable ssh access to root user which will protect the server from any attacks. Its kind of additional security layer on top of firewall.

There are 2 ways to disable SSH access to root.

With DenyUsers:

In /etc/ssh/sshd_config file search for line DenyUsers, if it exists edit it as follows else add following line:

DenyUsers root

If you want to disable ssh login for multiple users on the server add as following:

DenyUsers root user1 user2 user3

After updating sshd_config add restart sshd service with following command:

$ service sshd restart

Now try to ssh to root, it should not allow login even though you entered right password.

With PermitRootLogin:

PermitRootLogin will support 2 options “yes” and “no”.

Option yes will allow ssh to root and option no wont allow ssh to root.

To allow ssh to root add following line in /etc/ssh/sshd_config file and restart sshd service:

PermitRootLogin yes

To disable ssh to root add following line in /etc/ssh/sshd_config file and restart sshd service:

PermitRootLogin no

-Sany