Setting up SFTP and other things you can do on a Linux server

In Some tips on downloading and uploading DCPs and large files I wrote about the different ways I send large files:

  • Filemail
  • IBM Aspera
  • Amazon s3
  • and a dedicated SFTP server

    Here are some tips on using a dedicated SFTP server running Ubuntu 20.04/22.04.

Start the OpenSSH server

The OpenSSH server is already running on Ubuntu server, but if you are using Ubuntu Desktop you can install and start the Openssh server.

sudo apt update
sudo apt install openssh-server
sudo systemctl status ssh

Recommended SSH client

On Mac, I use terminal. On Windows I use Ubuntu on WSL.

To connect to the server.

ssh root@

Setting up basic security

Generating good passwords

sudo apt install pwgen

Generate a 12 digit password

pwgen 12 1


Use nftables firewall to accept only port 22 SSH/SFTP. If Nftables is not installed you can install it and start it with these commands.

sudo apt update
sudo apt install nftables
sudo systemctl enable nftables
sudo systemctl start nftables
sudo systemctl status nftables

Edit nftables.conf with modified Simple ruleset for a server to only accept SSH/SFTP on port 22 and alternative port 2222

tcp dport { 22, 2222 } accept
sudo nano /etc/nftables.conf

Restart nftables

sudo systemctl restart nftables

List the NFT ruleset

sudo nft list ruleset

Stop brute force attacks with sshguard and nftables

Install nftables if necessary

Set up sshguard

sudo apt install sshguard

Add sshg-fw-nft-sets to BACKEND= in sshguard-conf if needed

sudo nano /etc/sshguard/sshguard.conf

on Raspberry Pi


Start sshguard

sudo systemctl enable sshguard
sudo systemctl restart sshguard
sudo systemctl status sshguard

Soon you will see blocked IP addresses when you list the NFT ruleset

sudo nft list ruleset

Make chroot jail sftp users that can download and upload only from a folder in their home directory

To enable SFTP with chrooted users, you manually edit sshd_config to disable shell login. And then manually add chrooted users.

You can also use shell scripts like these made by Matthieu Petiteau on GitHub to do this faster.

Change these settings in /etc/ssh/sshd_config

nano /etc/ssh/sshd_config

Put a comment # before this line


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

Add this line

Subsystem sftp internal-sftp

add the group sftpusers

Match Group sftpusers
ChrootDirectory %h
ForceCommand internal-sftp
AllowTcpForwarding no
X11Forwarding no

Make a download user called user1 that can download and upload to only /home/user1/data

sudo groupadd sftpusers
sudo useradd -g sftpusers -s /usr/bin/false -m -d /home/user1 user1
sudo passwd user1
sudo chown root:root /home/user1
sudo chmod 755 /home/user1/
sudo mkdir /home/user1/data
sudo chown user1:sftpusers /home/user1/data
sudo chmod 755 /home/user1/data
sudo systemctl restart sshd.service

Updating the server regularly

It is essential to update the server regularly if you are running an unmanaged server.

sudo apt update
sudo apt upgrade
sudo apt dist-upgrade

Make a user with sudo privileges instead of using root

When Ubuntu is installed, you have root access and can log on to the server in an SSH shell with the root account. For better security, make a user with Sudo privileges that is used instead of root.

sudo adduser newuser

usermod -aG sudo newuser

Getting a root shell when logged in as a user with sudo privileges

sudo su -l

Disable PermitRootLogin yes from /etc/ssh/sshd_config

When you have a sudoer user, you can disable ssh root login. Comment PermitRootLogin yes in sshd_config to disable root access.

sudo apt install nano
sudo nano /etc/ssh/sshd_config
#PermitRootLogin yes 

@Restart the sshd service

sudo systemctl restart sshd.service 

Backup or copy data to another linux server with rsync over ssh

Sync a directory and subdirectories to another server.

rsync -aP /home/user/data/ download1@

Other things you can do on a Linux server

Moving a folder and change the permission of the folder to another user

sudo chown -R olduser:olduser /home/olduser/
sudo mv -R /home/olduser/ /home/olduser2/

Logging on to the server with SSH and downloading a DCP folder or video files from another SFTP/FTP server

Sometimes it can be nice to download something directly from FTP servers to the server. In Terminal, you can use SSH to log in to the server and use the command screen to detach from the session so you can resume it if the connection to the server is broken.

ssh user@

If I want to download something to a folder /home/user/download/newfolderwiththings.

cd /home/user/download
mkdir newfolderwiththings
sudo apt update
sudo apt install ncftp
sudo apt install screen
ncftp -u username

When you have started ncftp you can use:

  • get -R to download a folder and subdirectories.
  • ls to list the content
  • cd to change directories.
cd folder
get -R /folderwithhings

Detach from the screen by using control + a,d

When connecting to the ssh server again, use screen -r to attach to the session again.

screen -r 

If you have started many screen sessions, you will get a list of sessions so you can choose which to start. To exit a screen session, you can use


Compress and uncompress files on the server

You can make a 7z compressed archive of files on the server so it would be faster to download them. You can also upload an archive and then uncompress it on the server. You can also split the archive into parts so you can download many parts at once. You can use screen to quit the ssh session while the files are being compressed.

Install 7z

sudo apt update
sudo apt install p7zip p7zip-rar p7zip-full 

Compress a folder and its subdirectories

7z a -r directory.7z /directory

Compress a file

7z a archive.7z file.wav

Compress a directory and subdirectories. Normal compression.

Useful for wav files and similar files that will compress to half the size. Split into 3 GB parts. Cyberduck’s default setting is segmented downloads, but it can speed up uploads and downloads to split files into parts.

7z a -r -v3000m directory.7z  /directory

Compress file. Using -mx0 for no compression. Split into 3 GB parts. Useful to make the archive faster and for files that don’t compress much like prores video files.

7z a -mx0 -v3000m archive.7z

You can also upload 7z archive files and extract them on the server.
Extract archive recursively and keep the subdirectories

7z x archive.7z

Making an MD5 checksum file of files in a directory

You can check the MD5 checksum of a file on the server with the command

md5sum file

To test the integrity of a folder with files, you can have md5 text checksum files. You can make a checksum.md5 file for files in a directory like this:

md5sum * > checksums.md5

To check the checksum of the files in a directory with the md5 checksum file, you can use

md5sum -c checksums.md5

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