sysctl

Gambina's dream is to become a GNU/Linux kernel developer one day, but she has to go about it in several discrete steps:

1. Become very familiar with the GNU/Linux Fundamentals by getting an LPIC certification.
2. Get more advanced by obtaining an LFCS cert.
3. Get even more advanced by completing advanced Red Hat certs.
4. Build GNU/Linux from scratch, and then deep dive into the GNU/Linux kernel.

Today, Gambina wants to increase her knowledge of the sysctl command. Please give her several command examples in 3 categories: 1.) basic 2.) moderate 3.) advanced

Certainly! Here are examples of the sysctl command in three categories: basic, moderate, and advanced, to help Gambina increase her knowledge:

1. Basic:

   a) Display all available sysctl variables:

   sysctl -a

   This command displays the values of all available sysctl variables on the system.

   b) Display the value of a specific sysctl variable:

   sysctl kernel.hostname

   This command displays the value of the "kernel.hostname" sysctl variable, which represents the hostname of the system.

2. Moderate:

   a) Modify the value of a sysctl variable temporarily:

   sysctl -w net.ipv4.ip_forward=1

   This command sets the value of the "net.ipv4.ip_forward" sysctl variable to 1, enabling IP forwarding. The change is effective until the next system reboot.

   b) Load sysctl settings from a file:

   sysctl -p /etc/sysctl.conf

   This command loads sysctl settings from the "/etc/sysctl.conf" file. It applies the configured values persistently across system reboots.

3. Advanced:

   a) Modify sysctl variables persistently:

   echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf sysctl -p

   This sequence of commands appends the "net.ipv4.ip_forward=1" line to the "/etc/sysctl.conf" file, enabling IP forwarding persistently. The sysctl -p command then reloads the sysctl settings.

   b) Change the maximum number of open files (ulimit) system-wide:

   echo "fs.file-max = 100000" >> /etc/sysctl.conf sysctl -p ulimit -n 100000

   This sequence of commands modifies the "fs.file-max" sysctl variable in "/etc/sysctl.conf" to increase the maximum number of open files to 100,000. The sysctl -p command reloads the sysctl settings, and the ulimit -n command sets the ulimit system-wide.

These examples cover a range of scenarios to help Gambina understand the sysctl command at different levels. It's important to note that modifying sysctl variables requires proper understanding and consideration of their effects on the system. Gambina should consult the relevant documentation and exercise caution when making changes.