Where are SSH Authorized Keys Stored in Ubuntu

This article explains the exact file location where authorized SSH public keys are stored on a remote Ubuntu Linux server. It covers the directory path, how the file functions for user authentication, and the essential file permissions required to keep the connection secure.

On an Ubuntu Linux server, the authorized SSH public keys for a specific user are stored in a file named authorized_keys.

This file is located within a hidden directory called .ssh inside the user’s home directory. The absolute path to the file is:

/home/username/.ssh/authorized_keys

For the root user, the path is:

/root/.ssh/authorized_keys

How the Authorized Keys File Works

The authorized_keys file acts as a database of trusted public keys allowed to log into that specific user account. Each public key is stored as a single, continuous line of text. When you attempt to connect to the Ubuntu server via SSH using a private key, the SSH daemon (sshd) compares your private key against the corresponding public keys listed in this file. If a match is found, access is granted.

Required Directory and File Permissions

For security reasons, the SSH daemon will ignore the authorized_keys file if its permissions, or the permissions of its parent directory, are too open. To ensure secure and successful connections, set the following permissions:

1. The .ssh directory must be private to the owner. Set its permissions to 700:

   chmod 700 ~/.ssh

2. The authorized_keys file must only be readable and writable by the owner. Set its permissions to 600:

   chmod 600 ~/.ssh/authorized_keys

Both the directory and the file must also be owned by the user you are trying to log in as, which can be configured using the chown command if necessary.