SFTP journey

 To set up an SFTP server for your existing user karl, allowing uploads to /var/www and its subdirectories while still providing SSH access without restricting him to SFTP only, follow these steps:

Prerequisites

• Ensure you have root or sudo access to the server.
• OpenSSH server should be installed.

Steps

1. Open SSH Configuration File:

   sudo nano /etc/ssh/sshd_config

2. Add/Modify SFTP Configuration: Find the section related to Subsystem sftp. If it exists, it may look like this:

   Subsystem sftp /usr/lib/openssh/sftp-server

   If it doesn't exist, you can add it. After that, add a new section for the karl user. Place this below the Subsystem sftp line:

   Match User karl
       ChrootDirectory /var/www
       ForceCommand internal-sftp
       AllowTcpForwarding no
       X11Forwarding no
   

3. Set Permissions: The ChrootDirectory must be owned by root and not writable by anyone else. Adjust permissions as follows:

   sudo chown root:root /var/www
   sudo chmod 755 /var/www
   

   For any subdirectories where karl should upload files, you can set ownership to karl:

   sudo mkdir /var/www/uploads
   sudo chown karl:karl /var/www/uploads
   

4. Restart SSH Service: After making changes, restart the SSH service to apply the configuration:

   sudo systemctl restart sshd

5. Testing:

   • Log in as karl using SFTP:

     sftp karl@caputxeta

   • Try uploading a file to the uploads directory:

     put local_file.txt uploads/

   • Ensure you can still log in via SSH:

     ssh karl@caputxeta

Note

• The ChrootDirectory should be a directory that karl has permissions to write to. If karl needs to upload files to multiple directories under /var/www, you might need to repeat the ownership and permissions steps for each directory where uploads are needed.
• If you have any existing files in /var/www that need to be accessible to karl, you may want to adjust their permissions accordingly.

Troubleshooting

• If you encounter issues with SFTP access, check the SSH logs for error messages:

  sudo tail -f /var/log/auth.log

• Ensure that there are no syntax errors in the SSH configuration by running:

  sudo sshd -t

This setup allows karl to use SFTP for file uploads while still having SSH access to the server for other tasks.