There are several installation in linux/centos platform which needs specific run level.
Basically if you are running linux/centos in a graphic mode, its a run level 5, You may find some errors while installing some packages which says, you need to perform the installation in run level 3 and right now you are in run level 5.
Run Level 3 means you need to perform installation in a text mode only.
If you face such issue while installing your package, You need to follow the following steps.
Note: You must be logged in as a root. We will edit inittab file
Assuming you are in graphic mode which is run level 5, and we will change it to run level 3 which is text mode only.
Step 1. Right click on free space and open terminal.
Step 2. Type the command: sudo ls /etc | grep inittab
Step 3. In order to edit inittab file, Type command: sudo nano /etc/inittab
Now you will find that initab file is open,
Step 4. Now scroll down to find text id:5:intidefault
Step 5. Replace number 5 with 3. id:3:intidefault
Step 6. Now press ctrl 0 to save file and ctrl x and enter.
Step 7. Now we made changes in inittab file and saved it. Just type reboot and your machine will reboot in run level 3 i.e text mode only.
To watch video follow the below link: