Configure kernel parameters, persistent and non-persistent

Leon is a RHEL Sysadmin at cPanel:

• His RHEL Server: RHEL_Server_023
• His username: leon.panetta@cpanel.net
• His professional preference: competent RHEL Engineers NEVER run Linux commands as the root user.
• His objective: Configure kernel parameters, persistent and non-persistent.

Leon is studying for his LFCS exam, and he wants to master this objective:

Configure kernel parameters, persistent and non-persistent.

Please generate and explain all of the commands that he will need to master to master this objective.

To configure kernel parameters, both persistent (across reboots) and non-persistent (applied immediately but not saved for future reboots), Leon can use various commands and configuration files in Red Hat Enterprise Linux (RHEL). Here are the commands he needs to master for this objective:

1. sysctl: The sysctl command is used to configure kernel parameters in RHEL. It allows both persistent and non-persistent changes.

   To view the current value of a kernel parameter:

   • sysctl parameter_name
   • To change a kernel parameter temporarily (non-persistent):
   • sysctl -w parameter_name=new_value

   • To change a kernel parameter permanently (persistent):

     • Edit the /etc/sysctl.conf file and add or modify the parameter. For example:

     • parameter_name = new_value
       
   • To apply the changes from /etc/sysctl.conf without rebooting, run:
   • sysctl -p

2. sysctl.d: The /etc/sysctl.d/ directory contains configuration files for kernel parameters. Each file corresponds to a specific parameter or group of parameters.

   To add a new configuration file for a kernel parameter:

   • Create a new file in the /etc/sysctl.d/ directory with a .conf extension, such as /etc/sysctl.d/my_parameters.conf.

   • Add the parameter and its desired value to the file. For example:

   • parameter_name = new_value
   • After creating or modifying the file, run the following command to apply the changes:
   • sysctl --system

3. /etc/default/grub: The /etc/default/grub file is used to configure kernel boot parameters.

   To configure kernel boot parameters:

   • Edit the /etc/default/grub file using a text editor.

   • Modify the GRUB_CMDLINE_LINUX line to add or modify kernel boot parameters. For example:

   • GRUB_CMDLINE_LINUX="parameter_name=new_value"
   • After saving the changes, update the GRUB configuration by running:
   • grub2-mkconfig -o /boot/grub2/grub.cfg

4. tune2fs: The tune2fs command is used to configure file system parameters for ext2, ext3, and ext4 file systems.

   To configure file system parameters:

   • Identify the partition for which you want to configure parameters, such as /dev/sda1.
   • Use the tune2fs command with appropriate options to set the desired parameters. For example, to set the maximum mount count before running a file system check:
   • tune2fs -c max_mount_count /dev/sda1
   • Note: The tune2fs command is specific to ext2, ext3, and ext4 file systems.

These are some of the commands Leon needs to master in order to configure kernel parameters, both persistently and non-persistently, in Red Hat Enterprise Linux. Remember, it's crucial to exercise caution while modifying kernel parameters, as incorrect settings can lead to system instability or other issues.