Frequently Asked Question

Can I create my own custom runlevel in Linux?

Yes, it is possible to create our own custom runlevel by defining the necessary services and processes to be started or stopped in that runlevel but to do so user should have Indepth and advanced knowledge in Linux System Administration.

 What is the difference between runlevel 3 and runlevel 5?

Runlevel 5 and 3 are similar in functionality but the key difference is that runlevel 5 supports the graphical user interface (GUI) login prompt whereas runlevel 3 does not have graphical user interface (GUI) but both have multi-user mode with networking, where all essential services and processes required for a basic system operation, including networking services, are started.

What is the purpose of the single-user mode or maintenance mode (Runlevel 1)?

Runlevel 1 is also known as single-user mode or maintenance mode which is used for system maintance and repair. In this mode all other services and processes are stopped, only essential services and processes are started.

 Can I switch between runlevels without rebooting the system?

Yes, we can do that by using `init` command with the appropriate runlevel number.

For Example: If we want to change to runlevel 3

sudo init 3

A run level is a state of init and the whole system defines what system services are operating. Run levels are identified by numbers. Runlevel is a mode or state in which a Linux system operates. It has a crucial role in the management of the Linux System.

• Whenever a LINUX system boot, firstly the init process is started which is actually responsible for running other start scripts which mainly involves initialization of your hardware, bringing up the network, and starting the graphical interface.
• Now, the init first finds the default runlevel of the system so that it can run the start scripts corresponding to the default run level.
• A runlevel can simply be thought of as the state your system enters like if a system is in a single-user mode it will have a runlevel 1 while if the system is in a multi-user mode, it will have a runlevel 5.
• A runlevel, in other words, can be defined as a preset single-digit integer for defining the operating state of your LINUX or UNIX-based operating system. Each runlevel designates a different system configuration and allows access to different combinations of processes.

The important thing to note here is that there are differences in the runlevels according to the operating system. The standard LINUX kernel supports these seven different runlevels :