On certain occasions, a Systems Administrator may need to create a user account and restrict their access to only manage their own files via sFTP, but not be able to login to the system using any other means. The solution introduced in this article will show you how to accomplish this task.
To get hands-on experience, you need to deploy a Vultr CentOS 7 x64 server instance. Please note that the instructions for other Linux distributions may be different.
Additionally, all commands in this article are suitable for the
root; as such, you would need
sudo privileges if you are using a non-root user.
groupadd sftpusers useradd -g sftpusers -s /sbin/nologin user1 passwd user1
Here, the group
sftpusers is a dedicated sFTP group, the user
user1 is a dedicated sFTP user which is forbidden to log in using SSH.
Open the configuration file of the sshd service:
Find the line:
Subsystem sftp /usr/libexec/openssh/sftp-server
Replace it with:
Subsystem sftp internal-sftp
Append the following lines to the end of the file. The group name
sftpusers should be the same as the one you specified earlier.
Match Group sftpusers X11Forwarding no AllowTcpForwarding no ChrootDirectory %h ForceCommand internal-sftp
Save and quit:
Restart the sshd service to put your changes into effect.
systemctl restart sshd.service
You need to specify a directory for the sFTP-only user and make sure that this user can only play around in this directory:
chown -R root /home/user1 chmod -R 755 /home/user1 mkdir /home/user1/files chown user1. /home/user1/files
Now, the user
user1 can only upload and/or download files in the directory
/home/user1/files, he or she can never touch other users' files.
If you need more sFTP-only users, you can create them in the same fashion:
useradd -g sftpusers -s /sbin/nologin user2 passwd user2 chown -R root /home/user2 chmod -R 755 /home/user2 mkdir /home/user2/files chown user2. /home/user2/files
That's it. Each user account created in this fashion will be denied if you use it to log in the system. These user accounts can be used only in sFTP programs.