Configure sftp server

sftp server is an ftp server, but using ssh protocol. To set up one, please follow below steps.

First, create a directory to keep the uploaded data

$ sudo mkdir /data

Then, create a special group for sftp users

$ sudo groupadd sftp_users

Next, create a user called newuser that doesn't have regular login privileges, as a member of the newly created group, home directory set to /upload, and shell set to /sbin/nologin.

$ sudo useradd -g sftp_users -d /upload -s /sbin/nologin newuser

Set a password for the new user

$ sudo passwd newuser

Create an sftp directory for the new user, and set proper permissions for the directory

$ sudo mkdir -p /data/newuser/upload

$ sudo chown -R root:sftp_users /data/newuser

$ sudo chown -R newuser:sftp_users /data/newuser/upload

Add below lines to the end of /etc/ssh/sshd_config. Use any text editor that you are familiar with. Save the file once done.

Match Group sftp_users

ChrootDirectory /data/%u

ForceCommand internal-sftpd 

Test /etc/ssh/sshd_config for any syntax error

$ sudo sshd -t -f /etc/ssh/sshd_config

Restart ssh if no error reported from the above command

$ sudo systemctl restart sshd

Now we can use the user to upload or download data from the server

$ sftp newuser@server.ip.add.ress

Use "get" command to download, and "put" command to upload file.

We can also use applications like winscp and filezilla, to get a user interface.