CentOS/Grub: Difference between revisions
< CentOS
(Created page with " grub2-mkconfig -o /boot/grub2/grub.cfg <pre> # grub2-mkconfig -o /boot/grub2/grub.cfg Generating grub configuration file ... Adding boot menu entry for UEFI Firmware Settings ... done </pre> performance tweaks /etc/default/grub <pre> # vim grub GRUB_TIMEOUT=60 GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" #GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet splash selinux=0" #GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet splash intel_pst...") |
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= CentOS 9 = | |||
== Generate Grub Config == | |||
grub2-mkconfig -o /etc/grub2.cfg | |||
# OR | |||
grub2-mkconfig -o /etc/grub2-efi.cfg | |||
# OR | |||
grub2-mkconfig -o /boot/grub2/grub.cfg | grub2-mkconfig -o /boot/grub2/grub.cfg | ||
# OR | |||
grub2-mkconfig -o "$(readlink -e /etc/grub2.cfg)" | |||
# ls -la /etc/grub2.cfg | |||
lrwxrwxrwx. 1 root root 22 Nov 4 07:47 /etc/grub2.cfg -> ../boot/grub2/grub.cfg | |||
# ls -la /etc/grub2-efi.cfg | |||
lrwxrwxrwx. 1 root root 22 Nov 4 07:47 /etc/grub2-efi.cfg -> ../boot/grub2/grub.cfg | |||
# It is automatically generated by grub2-mkconfig using templates | |||
# from /etc/grub.d and settings from /etc/default/grub | |||
- | |||
Note, I like this version: <ref>https://unix.stackexchange.com/questions/152222/what-is-the-equivalent-of-update-grub-for-rhel-fedora-and-centos-systems</ref> | |||
grub2-mkconfig -o "$(readlink -e /etc/grub2.conf)" | |||
better than this, because if the file doesn't exist, it will dump it to the screen, instead of creating a file | |||
grub2-mkconfig -o $(readlink -f /etc/grub2.conf) | |||
=== Example === | |||
<pre> | |||
# grub2-mkconfig -o /etc/grub2.cfg | |||
Generating grub configuration file ... | |||
Adding boot menu entry for UEFI Firmware Settings ... | |||
done | |||
</pre> | |||
<pre> | |||
# grub2-mkconfig -o /etc/grub2-efi.cfg | |||
Generating grub configuration file ... | |||
Adding boot menu entry for UEFI Firmware Settings ... | |||
done | |||
</pre> | |||
<pre> | <pre> | ||
| Line 9: | Line 50: | ||
</pre> | </pre> | ||
performance tweaks | <pre> | ||
# grub2-mkconfig -o /etc/grub2-efi.cfg | |||
Generating grub configuration file ... | |||
Found Windows Boot Manager on /dev/sdb1@/efi/Microsoft/Boot/bootmgfw.efi | |||
Found Ubuntu 24.04.1 LTS (24.04) on /dev/sdb5 | |||
Adding boot menu entry for UEFI Firmware Settings ... | |||
done | |||
</pre> | |||
== Save Default Selection On Boot == | |||
Edit /etc/default/grub | |||
<pre> | |||
GRUB_TIMEOUT=60 | |||
GRUB_DEFAULT=saved | |||
GRUB_SAVEDEFAULT=true | |||
</pre> | |||
Regenerate the configuration using | |||
grub2-mkconfig -o /boot/grub2/grub.cfg | |||
== performance tweaks == | |||
/etc/default/grub | /etc/default/grub | ||
<pre> | <pre> | ||
| Line 15: | Line 78: | ||
GRUB_TIMEOUT=60 | GRUB_TIMEOUT=60 | ||
GRUB_DEFAULT=saved | GRUB_DEFAULT=saved | ||
GRUB_SAVEDEFAULT=true | |||
GRUB_DISABLE_SUBMENU=true | GRUB_DISABLE_SUBMENU=true | ||
GRUB_TERMINAL_OUTPUT="console" | GRUB_TERMINAL_OUTPUT="console" | ||
| Line 31: | Line 95: | ||
GRUB_DISABLE_RECOVERY="true" | GRUB_DISABLE_RECOVERY="true" | ||
</pre> | </pre> | ||
= keywords = | |||
Latest revision as of 02:02, 27 January 2026
CentOS 9
Generate Grub Config
grub2-mkconfig -o /etc/grub2.cfg # OR grub2-mkconfig -o /etc/grub2-efi.cfg # OR grub2-mkconfig -o /boot/grub2/grub.cfg # OR grub2-mkconfig -o "$(readlink -e /etc/grub2.cfg)"
# ls -la /etc/grub2.cfg lrwxrwxrwx. 1 root root 22 Nov 4 07:47 /etc/grub2.cfg -> ../boot/grub2/grub.cfg
# ls -la /etc/grub2-efi.cfg lrwxrwxrwx. 1 root root 22 Nov 4 07:47 /etc/grub2-efi.cfg -> ../boot/grub2/grub.cfg
# It is automatically generated by grub2-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub
-
Note, I like this version: [1]
grub2-mkconfig -o "$(readlink -e /etc/grub2.conf)"
better than this, because if the file doesn't exist, it will dump it to the screen, instead of creating a file
grub2-mkconfig -o $(readlink -f /etc/grub2.conf)
Example
# grub2-mkconfig -o /etc/grub2.cfg Generating grub configuration file ... Adding boot menu entry for UEFI Firmware Settings ... done
# grub2-mkconfig -o /etc/grub2-efi.cfg Generating grub configuration file ... Adding boot menu entry for UEFI Firmware Settings ... done
# grub2-mkconfig -o /boot/grub2/grub.cfg Generating grub configuration file ... Adding boot menu entry for UEFI Firmware Settings ... done
# grub2-mkconfig -o /etc/grub2-efi.cfg Generating grub configuration file ... Found Windows Boot Manager on /dev/sdb1@/efi/Microsoft/Boot/bootmgfw.efi Found Ubuntu 24.04.1 LTS (24.04) on /dev/sdb5 Adding boot menu entry for UEFI Firmware Settings ... done
Save Default Selection On Boot
Edit /etc/default/grub
GRUB_TIMEOUT=60 GRUB_DEFAULT=saved GRUB_SAVEDEFAULT=true
Regenerate the configuration using
grub2-mkconfig -o /boot/grub2/grub.cfg
performance tweaks
/etc/default/grub
# vim grub GRUB_TIMEOUT=60 GRUB_DEFAULT=saved GRUB_SAVEDEFAULT=true GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" #GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet splash selinux=0" #GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet splash intel_pstate=disable pcie_aspm.policy=performance pci=pcie_b us_perf noibrs noibpb nopti nospectre_v2 nospectre_v1 l1tf=off nospec_store_bypass_disable no_stf_barrier mds=off mi tigations=off intel_idle.max_cstate=0 idle=poll transparent_hugepage=never audit=0 selinux=0 nmi_watchdog=0 nohz=on clocksource=tsc nosoftlockup mce=ignore_ce cpuidle.off=1 skew_tick=1 processor.max_cstate=0 acpi_irq_nobalance" GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet splash intel_pstate=disable pcie_aspm.policy=performance pci=pcie_bu s_perf noibrs noibpb nopti nospectre_v2 nospectre_v1 l1tf=off nospec_store_bypass_disable no_stf_barrier mds=off mit igations=off intel_idle.max_cstate=0 idle=poll transparent_hugepage=never audit=0 selinux=0" GRUB_DISABLE_RECOVERY="true"