Modifying Runlevels on Linux

30 minutes
  • 5 Learning Objectives

About this Hands-on Lab

A runlevel is a specific mode of operation used by systems that implement System V initialization. In this lab, we are tasked with modifying runlevels for both CentOS and Ubuntu.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Configure the Runlevels on the CentOS Server
  1. Use the chkconfig command to disable the crond service for runlevels 2 and 4:

    chkconfig --level 24 crond off
  2. Use the chkconfig to enable the httpd service for runlevels 3 and 5:

    chkconfig --level 35 httpd on
Modify the Initialization Script for the Postfix Service on the CentOS Server
  1. Use a text editor to modify the init script for postfix at /etc/rc.d/init.d/postfix with the following changes:

  2. Update this line:

    # chkconfig: 2345 80 30

    To be:

    # chkconfig: 3 78 35
  3. Update this line:

    # Default-Start: 2 3 4 5

    To be:

    # Default-Start: 3
  4. Apply the changes.

  5. Remove the postfix service:

    chkconfig --del postfix
  6. Add the postfix service:

    chkconfig --add postfix
Remove the SysVinit Script Links for the Nginx Service on the Ubuntu server
  1. Use the update-rc.d command to remove init links for nginx:

    update-rc.d nginx remove
Enable the Lighttpd Service for Runlevels 2 and 5 on the Ubuntu server
  1. Use the update-rc.d command to enable lighttpd for runlevels 2 and 5:

    update-rc.d lighttpd enable 2 5
Create the Default SysVinit links for the Bluetooth Service on the Ubuntu server
  1. Use the update-rc.d command to add the defaults for the Bluetooth service:

    update-rc.d bluetooth defaults

Additional Resources

We, along with our team, are in charge of managing the various Linux systems at our company. In order to comply with the standards throughout the organization, we have been tasked with modifying the run levels for our CentOS and Ubuntu hosts.

For the CentOS hosts, we need to disable the crond service for runlevels 2 and 4. We also must enable the httpd service for runlevels 3 and 5. Then, we need to modify the initialization script for the postfix service with the following changes:

  • The service should only be enabled for runlevel 3.
  • The start priority should be 78.
  • The kill priority should be 35.

Once the script has been updated, the service needs to be deleted and added again to apply the changes.

For the Ubuntu hosts, remove the SysV init links for the nginx service. Then, enable the lighttpd service for runlevels 2 and 5. Finally, add the default SysV init links for the Bluetooth service.

Note: All tasks should be performed as the root user. Also, if a service is not installed as expected (i.e., httpd), this means that the lab has not completed initializing. You may need to wait a couple minutes until the initialization is complete.

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