CentOS 7
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Available in VPC
This guide describes how to update a kernel on the CentOS 7 server of NAVER Cloud Platform.
This guide is written based on new servers created on NAVER Cloud Platform, so there might be differences from the user server environment. User server environments may be affected by kernel updates and server restarts due to various reasons such as security hardening operations and various setting operations. Therefore, check the following before you perform a kernel update.
- Create a replicated server using Server image before updating a kernel of the actual server. Perform the kernel update on the replicated server and check if it restarts normally. When switching to operational status after restarting, check for any issues in the server. Proceed with the server kernel update only when no issues were found after through validation.
- In the case of GPU servers, the GPU driver that matches the kernel version must be installed for normal operation. If the updated kernel isn't compatible with GPU drivers, the GPU server might not function normally. Therefore, check GPU driver compatibility before you perform kernel updates. For related information, see GPU driver guide.
- NCP Repo is a repository provided by NAVER Cloud Platform to support user environments where external access is limited, such as VPC private subnet. NCP Repo may not provide the latest package.
Note
NAVER Cloud Platform has not tested all kernel versions after each update. As of January 1, 2024, the kernel version tested on CentOS 7 is 3.10.0-1160.102.1.el7.x86_64.
Caution
- The user is entirely responsible for performing user's server kernel updates. NAVER Cloud Platform does not take responsibility for issues caused by kernel updates.
- Normal server usage might be unavailable during kernel updates and restart, and recovery due to this is not supported. In addition, server recovery is not supported when the kernel update fails.
- Before updating the kernel, be sure to keep the backup created through Server image until it is no longer needed.
- No separate support is provided for problems related to this guide.
Update kernel
To update kernels for CentOS 7.3 and CentOS 7.8 servers, do the following:
Connect to the server you want to apply the kernel update to remotely.
Check the kernel version of the server.
- CentOS 7.3
[root@centos73 ~]# uname -r 3.10.0-514.2.2.el7.x86_64- CentOS 7.8
[root@centos78 ~]# uname -r 3.10.0-1127.10.1.el7.x86_64Check the repository information connected to the server.
[root@centos78 ~]# grep ^baseurl /etc/yum.repos.d/CentOS-Base.repo baseurl=http://mirror.ncloud.com/centos/$releasever/os/$basearch baseurl=http://mirror.ncloud.com/centos/$releasever/updates/$basearch/ baseurl=http://mirror.ncloud.com/centos/$releasever/extras/$basearch/ baseurl=http://mirror.ncloud.com/centos/$releasever/centosplus/$basearch/ baseurl=http://mirror.ncloud.com/centos/$releasever/contrib/$basearch/Download the Repo file using yum-config-manager.
- CentOS 7.3
To be able to use yum-config-manager, install the yum-utils package first and download the Repo file.
[root@centos73 ~]# rpm -qa | grep yum-utils | wc -l 0 [root@centos73 ~]# yum install yum-utils Loaded plugins: fastestmirror Determining fastest mirrors Resolving Dependencies --> Running transaction check ---> Package yum-utils.noarch 0:1.1.31-54.el7_8 will be installed --> Processing Dependency: python-kitchen for package: yum-utils-1.1.31-54.el7_8.noarch --> Running transaction check ---> Package python-kitchen.noarch 0:1.1.1-5.el7 will be installed --> Processing Dependency: python-chardet for package: python-kitchen-1.1.1-5.el7.noarch --> Running transaction check ---> Package python-chardet.noarch 0:2.2.1-3.el7 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================================================================================================================================= Package Arch Version Repository Size ================================================================================================================================================================================================= Installing: yum-utils noarch 1.1.31-54.el7_8 base 122 k Installing for dependencies: python-chardet noarch 2.2.1-3.el7 base 227 k python-kitchen noarch 1.1.1-5.el7 base 267 k Transaction Summary ================================================================================================================================================================================================= Install 1 Package (+2 Dependent packages) Total download size: 616 k Installed size: 2.8 M Is this ok [y/d/N]: y ... Omitted... Installed: yum-utils.noarch 0:1.1.31-54.el7_8 Dependency Installed: python-chardet.noarch 0:2.2.1-3.el7 python-kitchen.noarch 0:1.1.1-5.el7 Complete! [root@centos73 ~ ]# yum-config-manager --add-repo http://init.ncloud.com/server/linux/repo/centos7/CentOS-Base.repo Loaded plugins: fastestmirror adding repo from: http://init.ncloud.com/server/linux/repo/centos7/CentOS-Base.repo grabbing file http://init.ncloud.com/server/linux/repo/centos7/CentOS-Base.repo to /etc/yum.repos.d/CentOS-Base.repo repo saved to /etc/yum.repos.d/CentOS-Base.repo- CentOS 7.8
[root@centos78 ~ ]# yum-config-manager --add-repo http://init.ncloud.com/server/linux/repo/centos7/CentOS-Base.repo Loaded plugins: fastestmirror, langpacks adding repo from: http://init.ncloud.com/server/linux/repo/centos7/CentOS-Base.repo grabbing file http://init.ncloud.com/server/linux/repo/centos7/CentOS-Base.repo to /etc/yum.repos.d/CentOS-Base.repo repo saved to /etc/yum.repos.d/CentOS-Base.repo- CentOS 7.3
Check the changed repository information.
[root@centos78 ~ ]# grep ^baseurl /etc/yum.repos.d/CentOS-Base.repo baseurl=http://repo.ncloud.com/centos/$releasever/os/$basearch baseurl=http://repo.ncloud.com/centos/$releasever/updates/$basearch/ baseurl=http://repo.ncloud.com/centos/$releasever/extras/$basearch/ baseurl=http://repo.ncloud.com/centos/$releasever/centosplus/$basearch/ baseurl=http://repo.ncloud.com/centos/$releasever/contrib/$basearch/Check the kernel version provided by the repository.
[root@centos78 ~ ]# rm -rf /var/cache/yum/* [root@centos78 ~ ]# yum list kernel-3.10.0-1160.102.1.el7 Loaded plugins: fastestmirror, langpacks Loading mirror speeds from cached hostfile Available Packages kernel.x86_64 3.10.0-1160.102.1.el7 updateInstall the latest version of the kernel.
Carefully review the list of packages being newly installed, updated, or removed. If everything is in order, enteryto complete the installation.- CentOS 7.3
[root@centos73 ~ ]# yum install kernel-3.10.0-1160.102.1.el7 Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile Resolving Dependencies --> Running transaction check ---> Package kernel.x86_64 0:3.10.0-1160.102.1.el7 will be installed --> Processing Dependency: linux-firmware >= 20190429-72 for package: kernel-3.10.0-1160.102.1.el7.x86_64 --> Running transaction check ... Omitted... Dependencies Resolved ============================================================================================================================================================================ Package Arch Version Repository Size ============================================================================================================================================================================ Installing: kernel x86_64 3.10.0-1160.102.1.el7 update 52 M Updating: kexec-tools x86_64 2.0.15-51.el7_9.3 update 351 k selinux-policy-targeted noarch 3.13.1-268.el7_9.2 update 7.0 M Updating for dependencies: libselinux x86_64 2.5-15.el7 base 162 k libselinux-devel x86_64 2.5-15.el7 base 187 k libselinux-python x86_64 2.5-15.el7 base 236 k libselinux-utils x86_64 2.5-15.el7 base 151 k libsemanage x86_64 2.5-14.el7 base 151 k libsepol x86_64 2.5-10.el7 base 297 k libsepol-devel x86_64 2.5-10.el7 base 77 k linux-firmware noarch 20200421-80.git78c0348.el7_9 update 80 M policycoreutils x86_64 2.5-34.el7 base 917 k selinux-policy noarch 3.13.1-268.el7_9.2 update 498 k Transaction Summary ============================================================================================================================================================================ Install 1 Package Upgrade 2 Packages (+10 Dependent packages) Total download size: 142 M Is this ok [y/d/N]: y ... Omitted... Installed: kernel.x86_64 0:3.10.0-1160.102.1.el7 Updated: kexec-tools.x86_64 0:2.0.15-51.el7_9.3 selinux-policy-targeted.noarch 0:3.13.1-268.el7_9.2 Dependency Updated: libselinux.x86_64 0:2.5-15.el7 libselinux-devel.x86_64 0:2.5-15.el7 libselinux-python.x86_64 0:2.5-15.el7 libselinux-utils.x86_64 0:2.5-15.el7 libsemanage.x86_64 0:2.5-14.el7 libsepol.x86_64 0:2.5-10.el7 libsepol-devel.x86_64 0:2.5-10.el7 linux-firmware.noarch 0:20200421-80.git78c0348.el7_9 policycoreutils.x86_64 0:2.5-34.el7 selinux-policy.noarch 0:3.13.1-268.el7_9.2 Complete!- CentOS 7.8
[root@centos78 ~ ]# yum install kernel-3.10.0-1160.102.1.el7 Loaded plugins: fastestmirror, langpacks Loading mirror speeds from cached hostfile Resolving Dependencies --> Running transaction check ---> Package kernel.x86_64 0:3.10.0-1160.102.1.el7 will be installed --> Finished Dependency Resolution Dependencies Resolved ============================================================================================================================================================================ Package Arch Version Repository Size ============================================================================================================================================================================ Installing: kernel x86_64 3.10.0-1160.102.1.el7 update 52 M Transaction Summary ============================================================================================================================================================================ Install 1 Package Total download size: 52 M Installed size: 66 M Is this ok [y/d/N]: y ... Omitted... Installed: kernel.x86_64 0:3.10.0-1160.102.1.el7 Complete!After the installation is complete, check the bootable kernel version and the default boot kernel version.
- CentOS 7.3
[root@centos73 ~ ]# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2 CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-514.2.2.el7.x86_64) 7 (Core) CentOS Linux (0-rescue-7b63677441464f9a89b04041488122e0) 7 (Core) [root@centos73 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core)- CentOS 7.8
[root@centos78 ~ ]# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2 CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-1127.10.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-1127.el7.x86_64) 7 (Core) CentOS Linux (0-rescue-aaaeb22f90c34b3e90e68880b8553310) 7 (Core) [root@centos78 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core)NoteIf the installed kernel version does not appear, use the grub2-mkconfig command to recreate grub.cfg.
# grub2-mkconfig -o /boot/grub2/grub.cfg
:::
If the default boot kernel version is different from the installed kernel version, change the default boot kernel.
[root@centos78 ~ ]# ls -ld /etc/grub2* lrwxrwxrwx. 1 root root 22 Aug 31 2020 /etc/grub2.cfg -> ../boot/grub2/grub.cfg [root@centos78 ~ ]# grub2-mkconfig -o /etc/grub2.cfg Generating grub configuration file ... Found linux image: /boot/vmlinuz-3.10.0-1160.102.1.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-1160.102.1.el7.x86_64.img Found linux image: /boot/vmlinuz-3.10.0-1127.10.1.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-1127.10.1.el7.x86_64.img Found linux image: /boot/vmlinuz-3.10.0-1127.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-1127.el7.x86_64.img Found linux image: /boot/vmlinuz-0-rescue-aaaeb22f90c34b3e90e68880b8553310 Found initrd image: /boot/initramfs-0-rescue-aaaeb22f90c34b3e90e68880b8553310.img done [root@centos78 ~ ]# grub2-set-default "CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core)" [root@centos78 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core)NoteTo boot with a non-default kernel, change the kernel from the grub page when booting. If the wait time of the CentOS 7.3 grub page is short, see Extend wait time of CentOS 7.3 grub page to extend the wait time.
Reboot the server to activate the installed kernel version.
[root@centos78 ~ ]# rebootNoteIf the server reboot fails, it means the kernel update was not performed normally. In this case, see Restore kernel update to revert to the previous kernel version.
Log in to the server again and check if the new kernel is activated.
- CentOS 7.3
[root@centos73 ~ ]# uname -r 3.10.0-1160.102.1.el7.x86_64- CentOS 7.8
[root@centos78 ~ ]# uname -r 3.10.0-1160.102.1.el7.x86_64NoteTo check if the updated kernel is properly applied, see Checking kernel updates to check the kernel installation status.
Extend wait time of CentOS 7.3 grub page
To extend the wait time of the CentOS 7.3 grub page, do the following:
- Check the grub configuration file before you boot the server.
[root@centos73 ~ ]# grep GRUB_TIMEOUT /etc/default/grub GRUB_TIMEOUT=5 - Change the grub default configuration file and regenerate the grub.cfg file.
[root@centos73 ~ ]# sed -i "s/GRUB_TIMEOUT=5/GRUB_TIMEOUT=30/" /etc/default/grub [root@centos73 ~ ]# grep GRUB_TIMEOUT /etc/default/grub GRUB_TIMEOUT=30 [root@centos73 ~ ]# grub2-mkconfig -o /etc/grub2.cfg Generating grub configuration file ... Found linux image: /boot/vmlinuz-3.10.0-1160.102.1.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-1160.102.1.el7.x86_64.img Found linux image: /boot/vmlinuz-3.10.0-514.2.2.el7.x86_64 Found initrd image: /boot/initramfs-3.10.0-514.2.2.el7.x86_64.img Found linux image: /boot/vmlinuz-0-rescue-7b63677441464f9a89b04041488122e0 Found initrd image: /boot/initramfs-0-rescue-7b63677441464f9a89b04041488122e0.img done
Check kernel update
To check if the kernel update is applied normally, follow these steps:
- Connect to the server remotely.
- Check if the kernel package is installed.
[root@centos78 ~ ]# rpm -qa | grep kernel-3.10.0-1160.102.1.el7.x86_64 kernel-3.10.0-1160.102.1.el7.x86_64 - Check if the initramfs file and vmlinuz file are created in the /boot directory.
[root@centos78 ~ ]# ls -l /boot/initramfs-3.10.0-1160.102.1.el7.x86_64.img -rw------- 1 root root 21897039 Dec 4 11:00 /boot/initramfs-3.10.0-1160.102.1.el7.x86_64.img [root@centos78 ~ ]# ls -l /boot/initramfs-3.10.0-1160.102.1.el7.x86_64kdump.img -rw------- 1 root root 20211564 Dec 4 11:10 /boot/initramfs-3.10.0-1160.102.1.el7.x86_64kdump.img [root@centos78 ~ ]# ls -l /boot/vmlinuz-3.10.0-1160.102.1.el7.x86_64 -rwxr-xr-x 1 root root 7051880 Oct 18 00:46 /boot/vmlinuz-3.10.0-1160.102.1.el7.x86_64 - Check if the latest kernel settings are registered in the grub.cfg file.
[root@centos78 ~ ]# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2 CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-1127.10.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-1127.el7.x86_64) 7 (Core) CentOS Linux (0-rescue-aaaeb22f90c34b3e90e68880b8553310) 7 (Core) - Check the grub settings.
[root@centos78 ~ ]# grep GRUB_DEFAULT /etc/default/grub GRUB_DEFAULT=saved [root@centos78 ~ ]# cat /boot/grub2/grubenv # GRUB Environment Block saved_entry=CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) ... Omitted...
Restore kernel update
If you can't restart the server normally after a kernel update, you need to revert to the previous kernel before the update. You can revert it to one of the many installed kernel versions. This guide deals with how to revert the kernel to the version immediately before the update.
To restore the kernel version, follow these steps:
Note
To resolve server restart issues, you can attempt server recovery by entering single mode. For how to run reboot in Single Mode, see Server recovery guide.
Click the environment you are using in the Region menu and the Platform menu on the NAVER Cloud Platform console.
Click Services > Compute > Server, in order.
Click the Server menu.
Select the server to recover from the server image list, and then click the [Server connection console] button.
Select the previous version as the booting kernel from the grub booting page and reboot.
CentOS 7.3 grub boot page
CentOS 7.8 grub boot page
After booting is complete, check the server kernel version.
- CentOS 7.3
[root@centos73 ~ ]# uname -r 3.10.0-514.2.2.el7.x86_64- CentOS 7.8
[root@centos78 ~ ]# uname -r 3.10.0-1127.10.1.el7.x86_64Check the kernel version that is currently active.
- CentOS 7.3
[root@centos73 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) [root@centos73 ~ ]# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2 CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-514.2.2.el7.x86_64) 7 (Core) CentOS Linux (0-rescue-7b63677441464f9a89b04041488122e0) 7 (Core)- CentOS 7.8
[root@centos78 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) [root@centos78 ~ ]# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2 CentOS Linux (3.10.0-1160.102.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-1127.10.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-1127.el7.x86_64) 7 (Core) CentOS Linux (0-rescue-aaaeb22f90c34b3e90e68880b8553310) 7 (Core)Reset the default kernel version to the previous kernel version when booting.
- CentOS 7.3
[root@centos73 ~ ]# grub2-set-default "CentOS Linux (3.10.0-514.2.2.el7.x86_64) 7 (Core)" [root@centos73 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-514.2.2.el7.x86_64) 7 (Core)- CentOS 7.8
[root@centos78 ~ ]# grub2-set-default "CentOS Linux (3.10.0-1127.10.1.el7.x86_64) 7 (Core)" [root@centos78 ~ ]# grub2-editenv list saved_entry=CentOS Linux (3.10.0-1127.10.1.el7.x86_64) 7 (Core)NoteYou must change the default booting kernel when restoring the kernel because the default booting kernel settings were changed when updating to the latest kernel version. Otherwise, the server boots into the problematic kernel version on the next boot.
(Optional) Reboot the server to check whether the server boots up normally with the updated kernel version.
[root@centos78 ~ ]# reboot(Optional) Log back into the server to check the booting status and the kernel version.
- CentOS 7.3
[root@centos73 ~ ]# uname -r 3.10.0-514.2.2.el7.x86_64- CentOS 7.8
[root@centos78 ~ ]# uname -r 3.10.0-1127.10.1.el7.x86_64
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