Tips and Tricks - How to Use SFTP

April 3, 2012

Too often, new customers can get overwhelmed by a small administrative task on a Linux server. One of the more common questions I see in technical support is when a drive partition runs out of space. The website appears offline, and on of my coworkers advises you to just free-up some space. "Just?! Where can I find files that are deletable without affecting my website?"

Don't worry ... it's really quit simple. If you can use FTP (File Transfer Protocol), you can handle this bit of server management. Depending on the exact problem, we might instruct you to free up space by removing files in one of the following directories:

  • /var/log
  • /usr/local/cpanel
  • /usr/local/apache/logs
  • /usr/local/apache/domlogs

The reason these directories are usually overlooked is because they are not accessible by normal FTP users — users who only upload website content. When you upload website content to the server via FTP, the FTP user is limited to the directory structure for that website. Directories starting with "/var" and "/usr" cannot be accessed by these non-root users (The "root" user can access anything). And while root is a powerful user, for the sake of security, it is not normally allowed to log in over FTP because FTP is not secure ... That's where SFTP (Secure File Transfer Protocol) comes in.

Most FTP clients support SFTP, so you don't have to learn a new environment to securely access any file on the server. Every FTP client is different, but I'll illustrate with FileZilla because it's free and available on Mac, Windows and Linux. If you don't already have an FTP client, I highly recommend FileZilla. Because there are a few ways to use FileZilla to get an SFTP connection, I can share different options for you to try:

Quick Connect

The Quick Connect bar is the quickest way to connect to your server. Start FileZilla and look immediately under the toolbar for the Quick Connect bar:

SFTP Tutorial

Enter the hostname (IP address or domain name), “root” in the Username field, the root password in the Password field, and “22″ in the port field. Remember, port 22 is for SFTP, the same as SSH. Click the Quickconnect button to connect.

Using the Site Manager

The Site Manager lets you save your login details. Start FileZilla and you'll see the following:

SFTP Tutorial

To open the Site Manager, click the left-most icon in tool bar or go to File >> Site Manager in the menu.

SFTP Tutorial

Enter an IP address or domain name for your server in the Host field, and select "SFTP" as your protocol. You'll enter the root user's login information, and you're ready to connect by clicking the "Connect" button or you can click the "OK" button to save and close the dialog box.

If you just saved your settings and the Site Manager is not open, click the Site Manager icon again. From there, you can select the site under the "Select Entry" box, and you just have to click "Connect" to initiate the SFTP connection with your saved settings.

If you see a pop-up that warns of an "Unknown host key," clicking the "Always trust this host, add this key to the cache" option will prevent this interruption from showing in the future. Once you click "OK" to complete the connection, your FileZilla screen should look like this:

SFTP Tutorial

Notice the "Remote site" section on the middle right of the FileZilla screen:

SFTP Tutorial

This area in FileZilla is the directory and file listing of the server. Navigate the server's file structure here, and click "/" to access the top of the folder structure. You should see the "/usr" and "/var" directories, and you can explore the filesystem to delete the files technical support recommended to create space!

Message Log

If you have a problem connecting to your server by FTP or SFTP, the open area below the Quickconnect bar is the Message Log. If you can copy and paste this text into a ticket, you'll help technical support troubleshoot your connection problems. Below is an example log of a successful FTP session:

Status: Connecting to server.example.com...
Response:   fzSftp started
Command:    open "root@server.example.com" 22
Command:    Trust new Hostkey: Once
Command:    Pass: **********
Status: Connected to server.example.com
Status: Retrieving directory listing...
Command:    pwd
Response:   Current directory is: "/root"
Command:    ls
Status: Listing directory /root
Status: Calculating timezone offset of server...
Command:    mtime ".lesshst"
Response:   1326387703
Status: Timezone offsets: Server: -21600 seconds. Local: -21600 seconds. Difference: 0 seconds.
Status: Directory listing successful

And here's an example of a failed connection:

Status: Resolving address of example.com
Status: Connecting to 192.0.43.10:21...
Error:  Connection timed out
Error:  Could not connect to server
Status: Waiting to retry...
Status: Resolving address of example.com
Status: Connecting to 192.0.43.10:21...
Error:  Connection attempt interrupted by user

If you have any questions, leave them in a comment below. Enjoy your new-found SFTP powers!

-Lyndell