Linux - 修改内核启动顺序及删除无用内核
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现象：
CentOS7开机启动界面显示多个内核选项
原因：
正常情况下，有两个启动项，一个是“正常启动”，另一个是“救援模式启动”（rescue）。
如果启动项多于2个，说明当前系统有旧内核未删除。原因是CentOS更新后不会自动删除旧内核。
默认以新内核启动，可以在启动选项中临时选择，也可以修改配置永久指定。
示例：修改默认启动的内核
[[email protected] ~]# uname -r # 查看当前内核版本 3.10.0-693.5.2.el7.x86_64 [[email protected] ~]# [[email protected] ~]# cat /boot/grub2/grub.cfg |grep "menuentry " # 查看所有可用内核 menuentry ‘CentOS Linux (3.10.0-693.5.2.el7.x86_64) 7 (Core)‘ --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option ‘gnulinux-3.10.0-327.el7.x86_64-advanced-88ae7d3d-ffaf-4402-9d44-56b6845789e4‘ { menuentry ‘CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)‘ --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option ‘gnulinux-3.10.0-327.el7.x86_64-advanced-88ae7d3d-ffaf-4402-9d44-56b6845789e4‘ { menuentry ‘CentOS Linux (0-rescue-8405cda22c0b421db40478edcf9c1fb2) 7 (Core)‘ --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option ‘gnulinux-0-rescue-8405cda22c0b421db40478edcf9c1fb2-advanced-88ae7d3d-ffaf-4402-9d44-56b6845789e4‘ { [[email protected] ~]# [[email protected] ~]# grub2-set-default ‘CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)‘ [[email protected] ~]# [[email protected] ~]# grub2-editenv list # 查看内核修改结果 saved_entry=CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core) [[email protected] ~]#
示例：删除无用内核
[[email protected]OS-7 ~]# uname -r # 查看当前内核版本 3.10.0-693.5.2.el7.x86_64 [[email protected] ~]# [[email protected] ~]# rpm -qa |grep kernel-[0-9] # 查看全部内核包 kernel-3.10.0-693.5.2.el7.x86_64 kernel-3.10.0-327.el7.x86_64 [[email protected] ~]# [[email protected] ~]# yum remove kernel-3.10.0-327.el7.x86_64 # 删除指定的无用内核 Loaded plugins: fastestmirror, langpacks Resolving Dependencies --> Running transaction check ---> Package kernel.x86_64 0:3.10.0-327.el7 will be erased --> Finished Dependency Resolution Dependencies Resolved ============================================================================================================================================================= Package Arch Version Repository Size ============================================================================================================================================================= Removing: kernel x86_64 3.10.0-327.el7 @anaconda 136 M Transaction Summary ============================================================================================================================================================= Remove 1 Package Installed size: 136 M Is this ok [y/N]: y Downloading packages: Running transaction check Running transaction test Transaction test succeeded Running transaction Erasing : kernel-3.10.0-327.el7.x86_64 1/1 Verifying : kernel-3.10.0-327.el7.x86_64 1/1 Removed: kernel.x86_64 0:3.10.0-327.el7 Complete! [[email protected] ~]# [[email protected] ~]# rpm -qa |grep kernel-[0-9] # 查看全部内核包 kernel-3.10.0-693.5.2.el7.x86_64 [[email protected] ~]# [[email protected] ~]# cat /boot/grub2/grub.cfg |grep "menuentry " menuentry ‘CentOS Linux (3.10.0-693.5.2.el7.x86_64) 7 (Core)‘ --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option ‘gnulinux-3.10.0-327.el7.x86_64-advanced-88ae7d3d-ffaf-4402-9d44-56b6845789e4‘ { menuentry ‘CentOS Linux (0-rescue-8405cda22c0b421db40478edcf9c1fb2) 7 (Core)‘ --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option ‘gnulinux-0-rescue-8405cda22c0b421db40478edcf9c1fb2-advanced-88ae7d3d-ffaf-4402-9d44-56b6845789e4‘ { [[email protected] ~]#
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