firejail.sh

#!/bin/bash

apt-get -y update
apt-get -y install firejail

if [ ! -f "/etc/firejail/disable-common.local" ]; then
    cat > "/etc/firejail/disable-common.local" <<EOF

# Firejail blacklist
blacklist /etc/passwd
blacklist /etc/letsencrypt
blacklist /etc/mysql
blacklist /etc/nginx
blacklist /etc/php
blacklist /etc/postfix
blacklist /etc/varnish
blacklist /var/lib/mysql
blacklist /var/run/php

# END
EOF

fiw

On Ubuntu Server, you would install and configure it like this (e.g. in a firejail_install.sh script):
Just be careful what you blacklist :)

This, combined with the right permissions on /home should be enough to somewhat better protect your system from prying eyes.

The code snippet you provided is a Bash script that performs the following tasks:

1. #!/bin/bash: This line is known as a "shebang" and it tells the system to use the Bash shell interpreter to execute the script.

2. apt-get -y update: This command updates the package lists for the packages installed on the system. It helps to ensure that you have the latest information about the available package versions.

3. apt-get -y install firejail: This command installs the Firejail package on the system. Firejail is a security sandbox tool that restricts the running processes' access to system resources like files, directories, and device nodes.

4. if [ ! -f "/etc/firejail/disable-common.local" ]; then: This is an if statement that checks if the file /etc/firejail/disable-common.local does not exist. If the file does not exist, it executes the code block inside the then section.

5. cat > "/etc/firejail/disable-common.local" <<EOF ... EOF: This block of code creates a new file /etc/firejail/disable-common.local and writes the content between the <<EOF and EOF markers to the file. The content is a list of directories and files that Firejail will blacklist, meaning that any sandboxed process will not have access to these paths.

   The paths being blacklisted include:

   • /etc/passwd (system user account information)
   • /etc/letsencrypt (Let's Encrypt SSL/TLS certificates)
   • /etc/mysql (MySQL configuration files)
   • /etc/nginx (Nginx configuration files)
   • /etc/php (PHP configuration files)
   • /etc/postfix (Postfix mail server configuration files)
   • /etc/varnish (Varnish HTTP cache configuration files)
   • /var/lib/mysql (MySQL data directory)
   • /var/run/php (PHP runtime directory)

6. fi: This closes the if statement.

In summary, this script installs the Firejail package and creates a configuration file (/etc/firejail/disable-common.local) that blacklists access to specific system directories and files for any sandboxed processes launched with Firejail. This configuration helps to enhance security by restricting access to sensitive system resources for untrusted or potentially malicious applications running in the Firejail sandbox.