Fix SSH Permission Denied: Full Explanation & Expert Solution

Fix SSH Permission Denied: Full Explanation & Expert Solution

Table of Contents:

1. Introduction
2. Understanding SSH Permissions 2.1 Categories of Users in Linux 2.2 Permission Points 2.3 Setting Permissions for SSH Directory 2.4 Setting Permissions for Public Key 2.5 Setting Permissions for Private Key
3. Fixing "Permission Denied" Error 3.1 Renaming SSH Directory 3.2 Creating a New SSH Directory 3.3 Setting Permissions for SSH Directory 3.4 Creating Files for Public and Private Keys 3.5 Setting Permissions for Public and Private Keys 3.6 Authentication and Logging In using SSH Agent
4. Conclusion
5. Frequently Asked Questions (FAQs)

Understanding and Fixing Permission Denied Public Key Issue in Linux

Introduction As a user working on Linux servers, you may encounter the "Permission Denied" error when trying to log in using SSH and a different sandbox. This issue usually occurs when the SSH permissions are not properly set. In this article, we will discuss SSH permissions, understand the different user categories in Linux, and provide step-by-step instructions to fix the "Permission Denied" error.

Understanding SSH Permissions 2.1 Categories of Users in Linux In Linux, there are three categories of users: owner, group, and others. Each category has three sets of permissions: read, write, and execute. The owner has the highest level of control over a file or directory, followed by the group, and then others.

2.2 Permission Points Each category of users can have a certain number of permission points. For example, the owner can have 7 points (read: 4, write: 2, execute: 1), while the group and others may have different points based on their permissions.

2.3 Setting Permissions for SSH Directory To ensure the SSH directory remains private, it is recommended to set the permissions to 700. This means only the owner has permission to read, write, and execute the directory, while others have no access.

2.4 Setting Permissions for Public Key The public key, which should be public, can be set to 644. This allows the owner to read and write the file, while the group and others can only read it.

2.5 Setting Permissions for Private Key The private key, which should be kept private, should have permissions set to 600. This ensures that only the owner can read, write, and execute the file, while others have no access.

Fixing "Permission Denied" Error 3.1 Renaming SSH Directory If you encounter the "Permission Denied" error, you can try renaming the existing SSH directory in the root directory. This can be done by using the command mv .ssh old_ssh. Renaming the directory will allow You to Create a new SSH directory with the correct permissions.

3.2 Creating a New SSH Directory After renaming the existing SSH directory, create a new directory using the command mkdir .ssh. This new directory will be used to store the SSH files.

3.3 Setting Permissions for SSH Directory To set the correct permissions for the SSH directory, use the command sudo chmod 700 .ssh. This ensures that only the owner has full access to the directory.

3.4 Creating Files for Public and Private Keys Inside the SSH directory, create two files: one for the public key and one for the private key. Use the command touch id_rsa for the private key file, and touch id_rsa.pub for the public key file.

3.5 Setting Permissions for Public and Private Keys Set the correct permissions for the public and private key files. For the public key, use sudo chmod 644 id_rsa.pub, and for the private key, use sudo chmod 600 id_rsa. These permissions ensure proper access control for each file.

3.6 Authentication and Logging In using SSH Agent To authenticate and log in using the SSH agent, you need to specify the location of your private key. Use the command ssh-add /path/to/private_key. This allows you to securely log in to your server.

Conclusion By understanding SSH permissions and following the steps mentioned above, you can fix the "Permission Denied" error when logging in to your Linux server. Properly setting permissions for the SSH directory, public key, and private key ensures secure access control. Remember to always keep your private key private and the public key public.

Frequently Asked Questions (FAQs)

Q: Why am I getting a "Permission Denied" error when logging in via SSH? A: The "Permission Denied" error typically occurs when the SSH permissions are not set correctly. Ensure that the SSH directory, public key, and private key have the appropriate permissions.

Q: How do I set the correct permissions for the SSH directory? A: Set the permissions for the SSH directory to 700 using the command sudo chmod 700 .ssh. This ensures that only the owner has full access.

Q: What permissions should I set for the public and private keys? A: For the public key, set the permissions to 644 (sudo chmod 644 id_rsa.pub). For the private key, set the permissions to 600 (sudo chmod 600 id_rsa).

Q: Can I use different names for the public and private key files? A: Yes, you can choose different names for the public and private key files. Just make sure to update the file names accordingly in the SSH configuration.

Q: How can I ensure the security of my private key? A: Keep your private key secure by setting the permissions to 600, only allowing the owner to read, write, and execute it. Additionally, avoid sharing or exposing your private key.