更新 CentOS 7 的核心版本

為什麼要更新核心版本？
先前在維護 CentOS 7 的相關主機都是採用原本舊的 3.x 版本核心，在穩定的前提下，基本上都不會去變更核心的版本，但是在開發 OxOOL V4 的過程中，因為要測試大量的多人連線編輯工作效能，發現在新的 Rocky Linux 8 及 Ubuntu 20.0.4 的環境下，效能有不俗的躍進，故想測試看看 CentOS 7 在更新核心之後，在 OxOOL V4 的效能表現是否有改進，沒想到有不少的提升，故有本篇的記錄，所以接下來的說明，適用於以下的條件。 
 在 CentOS 7 環境下安裝 LAMP 應用 
 在 CentOS 7 環境下安裝 Nextcloud 應用 
 在 CentOS 7 環境下安裝 OxOOL 社群版、商用版應用(包含 V3、V4 版本)

確認目前 CentOS 7 的核心版本
在進行本項工作前，建議先將 CentOS 7 的版本更新至最新的 CentOS Linux release 7.9.2009 (Core) 版本，可以使用以下的指令確認： 
 # cat /etc/redhat-release
CentOS Linux release 7.9.2009 (Core) 
 然後確認一下目前系統的核心版本，指令如下： 
 # uname -a
Linux oxoolcommunity.ossii.com.tw 3.10.0-1160.66.1.el7.x86_64 #1 SMP Wed May 18 16:02:34 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux 
 目前 CentOS 7 最新的核心版本為： 3.10.0-1160.66.1.el7.x86_64 ，可以再使用 yum update 指令更新。 
 # yum update -y
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror01.idc.hinet.net
 * extras: mirror01.idc.hinet.net
 * updates: mirror01.idc.hinet.net
No packages marked for update

安裝最新的 Kernel，並移除舊的核心套件
請先匯入最新的核心來源，指令如下： 
 # rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm
正在擷取 http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm
正在擷取 http://elrepo.org/elrepo-release-7.0-4.el7.elrepo.noarch.rpm
正在準備… ################################# [100%]
Updating / installing...
 1:elrepo-release-7.0-4.el7.elrepo ################################# [100%] 
 然後安裝最新的核心 5.x 版本。 
 # yum --enablerepo=elrepo-kernel install kernel-ml -y
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror01.idc.hinet.net
 * elrepo: ftp.yz.yamagata-u.ac.jp
 * elrepo-kernel: ftp.yz.yamagata-u.ac.jp
 * extras: mirror01.idc.hinet.net
 * updates: mirror01.idc.hinet.net
elrepo | 3.0 kB 00:00
elrepo-kernel | 3.0 kB 00:00
(1/2): elrepo/primary_db | 580 kB 00:00
(2/2): elrepo-kernel/primary_db | 2.1 MB 00:00
Resolving Dependencies
--> Running transaction check
---> Package kernel-ml.x86_64 0:5.18.6-1.el7.elrepo will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package Arch Version Repository Size
================================================================================
Installing:
 kernel-ml x86_64 5.18.6-1.el7.elrepo elrepo-kernel 56 M

Transaction Summary
================================================================================
Install 1 Package

Total download size: 56 M
Installed size: 257 M
Is this ok [y/d/N]: y
Downloading packages:
kernel-ml-5.18.6-1.el7.elrepo.x86_64.rpm | 56 MB 00:05
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Warning: RPMDB altered outside of yum.
 Installing : kernel-ml-5.18.6-1.el7.elrepo.x86_64 1/1
 Verifying : kernel-ml-5.18.6-1.el7.elrepo.x86_64 1/1

Installed:
 kernel-ml.x86_64 0:5.18.6-1.el7.elrepo

Complete! 
 然後查詢一下目前有安裝在系統上的核心版本，指令如下： 
 # rpm -qa |grep kernel
kernel-tools-3.10.0-1160.66.1.el7.x86_64
kernel-3.10.0-1160.49.1.el7.x86_64
kernel-tools-libs-3.10.0-1160.66.1.el7.x86_64
kernel-3.10.0-1160.66.1.el7.x86_64
kernel-3.10.0-1160.53.1.el7.x86_64
kernel-3.10.0-1160.59.1.el7.x86_64
kernel-3.10.0-1160.62.1.el7.x86_64
kernel-ml-5.18.6-1.el7.elrepo.x86_64 
 接下來移掉舊版本的 kernel，以及其它核心的 tools、libs 套件，因為等一下要改安裝 kernel-5.18 的 libs、tools 等套件，會有衝突，故要先移除舊的， 不過要小心處理，不要移錯，不然有可能等一下開不了機！以本例來說，我們要移掉以下套件，範例如下。 
 # yum remove kernel-tools-3.10.0-1160.66.1.el7.x86_64 kernel-tools-libs-3.10.0-1160.66.1.el7.x86_64
Loaded plugins: fastestmirror
Resolving Dependencies
--> Running transaction check
---> Package kernel-tools.x86_64 0:3.10.0-1160.66.1.el7 will be erased
---> Package kernel-tools-libs.x86_64 0:3.10.0-1160.66.1.el7 will be erased
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package Arch Version Repository Size
================================================================================
Removing:
 kernel-tools x86_64 3.10.0-1160.66.1.el7 @updates 337 k
 kernel-tools-libs x86_64 3.10.0-1160.66.1.el7 @updates 18 k

Transaction Summary
================================================================================
Remove 2 Packages

Installed size: 355 k
Is this ok [y/N]:確認再按 y 鍵 
 移掉後，再查詢一下目前的 Kernel 版本。 
 # rpm -qa|grep kernel kernel-3.10.0-1160.49.1.el7.x86_64
kernel-3.10.0-1160.66.1.el7.x86_64
kernel-3.10.0-1160.53.1.el7.x86_64
kernel-3.10.0-1160.59.1.el7.x86_64
kernel-3.10.0-1160.62.1.el7.x86_64
kernel-ml-5.18.6-1.el7.elrepo.x86_64 
 除了 kernel-ml-5.18.6-1.el7.elrepo.x86_64 及 kernel-3.10.0-1160.66.1.el7.x86_64 外，其它舊版本都可以移掉了。 
 # yum remove kernel-3.10.0-1160.49.1.el7.x86_64 kernel-3.10.0-1160.53.1.el7.x86_64 kernel-3.10.0-1160.59.1.el7.x86_64 kernel-3.10.0-1160.62.1.el7.x86_64
Loaded plugins: fastestmirror
Resolving Dependencies
--> Running transaction check
---> Package kernel.x86_64 0:3.10.0-1160.49.1.el7 will be erased
---> Package kernel.x86_64 0:3.10.0-1160.53.1.el7 will be erased
---> Package kernel.x86_64 0:3.10.0-1160.59.1.el7 will be erased
---> Package kernel.x86_64 0:3.10.0-1160.62.1.el7 will be erased
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package Arch Version Repository Size
================================================================================
Removing:
 kernel x86_64 3.10.0-1160.49.1.el7 @updates 64 M
 kernel x86_64 3.10.0-1160.53.1.el7 @updates 64 M
 kernel x86_64 3.10.0-1160.59.1.el7 @updates 64 M
 kernel x86_64 3.10.0-1160.62.1.el7 @updates 64 M

Transaction Summary
================================================================================
Remove 4 Packages

Installed size: 257 M
Is this ok [y/N]:一樣確認後再按 y 鍵 
 再安裝新核心的表頭、libs 及 tools 套件。 
 # yum --enablerepo=elrepo-kernel install kernel-ml-headers kernel-ml-tools kernel-ml-tools-libs -y
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror01.idc.hinet.net
 * elrepo: ftp.ne.jp
 * elrepo-kernel: ftp.ne.jp
 * extras: mirror01.idc.hinet.net
 * updates: mirror01.idc.hinet.net
Resolving Dependencies
--> Running transaction check
---> Package kernel-ml-headers.x86_64 0:5.18.6-1.el7.elrepo will be installed
---> Package kernel-ml-tools.x86_64 0:5.18.6-1.el7.elrepo will be installed
---> Package kernel-ml-tools-libs.x86_64 0:5.18.6-1.el7.elrepo will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package Arch Version Repository Size
================================================================================
Installing:
 kernel-ml-headers x86_64 5.18.6-1.el7.elrepo elrepo-kernel 1.6 M
 kernel-ml-tools x86_64 5.18.6-1.el7.elrepo elrepo-kernel 267 k
 kernel-ml-tools-libs x86_64 5.18.6-1.el7.elrepo elrepo-kernel 152 k

Transaction Summary
================================================================================
Install 3 Packages

Total download size: 2.0 M
Installed size: 6.2 M
Downloading packages:
(1/3): kernel-ml-tools-5.18.6-1.el7.elrepo.x86_64.rpm | 267 kB 00:00
(2/3): kernel-ml-tools-libs-5.18.6-1.el7.elrepo.x86_64.rpm | 152 kB 00:00
(3/3): kernel-ml-headers-5.18.6-1.el7.elrepo.x86_64.rpm | 1.6 MB 00:00
--------------------------------------------------------------------------------
Total 2.6 MB/s | 2.0 MB 00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
 Installing : kernel-ml-tools-libs-5.18.6-1.el7.elrepo.x86_64 1/3
 Installing : kernel-ml-tools-5.18.6-1.el7.elrepo.x86_64 2/3
 Installing : kernel-ml-headers-5.18.6-1.el7.elrepo.x86_64 3/3
 Verifying : kernel-ml-headers-5.18.6-1.el7.elrepo.x86_64 1/3
 Verifying : kernel-ml-tools-5.18.6-1.el7.elrepo.x86_64 2/3
 Verifying : kernel-ml-tools-libs-5.18.6-1.el7.elrepo.x86_64 3/3

Installed:
 kernel-ml-headers.x86_64 0:5.18.6-1.el7.elrepo
 kernel-ml-tools.x86_64 0:5.18.6-1.el7.elrepo
 kernel-ml-tools-libs.x86_64 0:5.18.6-1.el7.elrepo

Complete! 
 最後再更新一下，確認是否還有其它更新套件。 
 # yum update -y
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror01.idc.hinet.net
 * elrepo: hkg.mirror.rackspace.com
 * extras: mirror01.idc.hinet.net
 * updates: mirror01.idc.hinet.net
Resolving Dependencies
--> Running transaction check
---> Package elrepo-release.noarch 0:7.0-4.el7.elrepo will be updated
---> Package elrepo-release.noarch 0:7.0-5.el7.elrepo will be an update
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package Arch Version Repository Size
================================================================================
Updating:
 elrepo-release noarch 7.0-5.el7.elrepo elrepo 8.6 k

Transaction Summary
================================================================================
Upgrade 1 Package

Total download size: 8.6 k
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
elrepo-release-7.0-5.el7.elrepo.noarch.rpm | 8.6 kB 00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
 Updating : elrepo-release-7.0-5.el7.elrepo.noarch 1/2
 Cleanup : elrepo-release-7.0-4.el7.elrepo.noarch 2/2
 Verifying : elrepo-release-7.0-5.el7.elrepo.noarch 1/2
 Verifying : elrepo-release-7.0-4.el7.elrepo.noarch 2/2

Updated:
 elrepo-release.noarch 0:7.0-5.el7.elrepo

Complete!

設定 grub 2 確認開機順序，並重新開機
先使用以下指令確認新的核心有在開機選單中： 
 # awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg
CentOS Linux (5.18.6-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-1160.66.1.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-db7214c5f0fd4b74abbce0498c2ad9b8) 7 (Core) 
 沒有的話，請確認前面的更新指令是否正確執行，接下來設定預設使用第 0 個核心版本的順位開機。 
 # grub2-set-default 0 
 重新開機，會看到開機時的核心選單已經更新完成。 
 
 登入後再確認一次核心版本： 
 # uname -a
Linux oxoolcommunity.ossii.com.tw 5.18.6-1.el7.elrepo.x86_64 #1 SMP PREEMPT_DYNAMIC Tue Jun 21 09:11:23 EDT 2022 x86_64 x86_64 x86_64 GNU/Linux 
 這樣就完成了核心升級的工作！