How do I permanently modify the kernel command line on RHEL 7?

Environment

• Red Hat Enterprise Linux (RHEL) 7
• GRUB2 boot loader

Issue

• How do I modify the kernel command line (and, thus, kernel boot parameters) in Red Hat Enterprise Linux 7 with GRUB2 installed as a boot loader?

Resolution

For RHEL7:

Alternative 1:

1. Make copy of the GRUB2 configuration files as a precaution:

   For a BIOS-based system:

   # cp /etc/default/grub /etc/default/grub-backup            
   # cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg-backup
   

   For a UEFI-based system:

   # cp /etc/default/grub /etc/default/grub-backup
   # cp /boot/efi/EFI/redhat/grub.cfg /boot/efi/EFI/redhat/grub.cfg-backup
   

2. Open the /etc/default/grub file for editing:

   # vi /etc/default/grub
   

   This file contains multiple GRUB2 options. Kernel boot parameters are specified by the GRUB_CMDLINE_LINUX option.

3. Once the file is edited, save it and run the command specified below to generate a new grub.cfg file:

   For a BIOS-based system:

   # grub2-mkconfig -o /boot/grub2/grub.cfg
   

   For a UEFI-based system:

   # grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
   

4. Finally, reboot the system to apply the changes:

   # systemctl reboot
   

Alternative 2: Using grubby command:

1. For checking details of default kernel:

# grubby --info DEFAULT

2. For adding parameters on all kernels:

# grubby --update-kernel=ALL --args="argA argB"

3. For removing parameters on all kernels:

# grubby --update-kernel=ALL --remove-args="argA argB"

4. Reboot the system to apply the changes:

# reboot

• For more information about grubby: refer to the documentation.

Additional Notes:

• For RHEL5 and RHEL6, see: How do I permanently modify the kernel command line in RHEL5 and RHEL6?

• For RHEL 8, see: How do I permanently modify the kernel command line in RHEL 8?

• For RHEL 9, see: How to modify the kernel command-line in Red Hat Enterprise Linux 9

• To make a one-time, non-persistent change at boot, please see: How to manually modify the boot parameter in grub before the system boots

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