When we trying to connect to an Oracle Cloud Linux/UNIX-Like Instance through Open SSH, the SSH client returns one of the following errors:
Issue:
"Disconnected: No supported authentication methods available (server sent: publickey)"
"Disconnected: No supported authentication methods available (server sent: publickey, gssapi-with-mic)"
Fix:
There are multiple issues that could cause such an error, please read below what the troubleshoot steps are for the most common causes.
1. Check that the IP address against which you try to connect is the address of the correct instance. This can be performed either through the Compute Console or the REST API:
Listing Instances in the Compute Console
Retrieving Details of an Instance using the REST API
Note that, unless reserved, the IP addresses of instances could change after reboots: Reserving a Public IP Address
2. Check that a SSH private key is configured in the SSH client you use or it is specified to the SSH/SCP/SFTP command.
3. Check that the SSH client/SSH agent (e.g. WinSCP, PuTTY, Pageant, etc) you use points to the correct directory containing the private SSH keys.
4. Check that the .pem private SSH key file has been converted successfuly to the .ppk format.
5. If you installed a new version of openssh-client or openssh-server, try to erase/purge the already installed version before installing the new one, for example:
sudo yum remove openssh-server
sudo yum -y install openssh-server openssh-clients
or, on some other Linux distros:
sudo apt-get purge openssh-server
sudo apt-get install openssh-server openssh-client
6. If you have another active SSH session/terminal open, check that the SSH daemon is running, by calling "sudo service sshd status" or, on some other distros, "sudo service ssh status". If it's stopped, try to start it.
7. If no other terminal is opened, generally an instance restart should restart the SSH daemon as well. You can also check in the web console whether or not the SSH daemon started during the boot: Viewing the Boot Log of an Instance
Issue:
"Disconnected: No supported authentication methods available (server sent: publickey)"
"Disconnected: No supported authentication methods available (server sent: publickey, gssapi-with-mic)"
Fix:
There are multiple issues that could cause such an error, please read below what the troubleshoot steps are for the most common causes.
1. Check that the IP address against which you try to connect is the address of the correct instance. This can be performed either through the Compute Console or the REST API:
Listing Instances in the Compute Console
Retrieving Details of an Instance using the REST API
Note that, unless reserved, the IP addresses of instances could change after reboots: Reserving a Public IP Address
2. Check that a SSH private key is configured in the SSH client you use or it is specified to the SSH/SCP/SFTP command.
3. Check that the SSH client/SSH agent (e.g. WinSCP, PuTTY, Pageant, etc) you use points to the correct directory containing the private SSH keys.
4. Check that the .pem private SSH key file has been converted successfuly to the .ppk format.
5. If you installed a new version of openssh-client or openssh-server, try to erase/purge the already installed version before installing the new one, for example:
sudo yum remove openssh-server
sudo yum -y install openssh-server openssh-clients
or, on some other Linux distros:
sudo apt-get purge openssh-server
sudo apt-get install openssh-server openssh-client
6. If you have another active SSH session/terminal open, check that the SSH daemon is running, by calling "sudo service sshd status" or, on some other distros, "sudo service ssh status". If it's stopped, try to start it.
7. If no other terminal is opened, generally an instance restart should restart the SSH daemon as well. You can also check in the web console whether or not the SSH daemon started during the boot: Viewing the Boot Log of an Instance
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