Linux CentOS 7.X 如何修改内核启动默认顺序

我们知道，centos 6.x是通过/etc/grub.conf就行内核启动顺序修改的，而且比较直观查看。但centos 7的系统和6就不一样了，是通过grub2为引导程序。下边简单说下centos 7的内核启动顺序如何修改。
1，首先查看当前系统有几个内核。比如：

1 2 3 4 5 6 7 8 9

[root@kunpeng42 ~]# cat /boot/grub2/grub.cfg |grep menuentry if [ x"${feature_menuentry_id}" = xy ]; then   menuentry_id_option="--id"   menuentry_id_option="" export menuentry_id_option menuentry 'CentOS Linux (4.4.161-1.el7.elrepo.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-4.20.13-1.el7.elrepo.x86_64-advanced-269d191a-7493-489c-917f-aafe8434bb38' { menuentry 'CentOS Linux (4.20.13-1.el7.elrepo.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-4.20.13-1.el7.elrepo.x86_64-advanced-269d191a-7493-489c-917f-aafe8434bb38' { menuentry 'CentOS Linux (4.20.12-1.el7.elrepo.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-4.20.12-1.el7.elrepo.x86_64-advanced-269d191a-7493-489c-917f-aafe8434bb38' { menuentry 'CentOS Linux (3.10.0-957.5.1.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-957.5.1.el7.x86_64-advanced-269d191a-7493-489c-917f-aafe8434bb38' { menuentry 'CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-693.el7.x86_64-advanced-269d191a-7493-489c-917f-aafe8434bb38' { menuentry 'CentOS Linux (0-rescue-87e40ba2fda2490c9440fae352527550) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-87e40ba2fda2490c9440fae352527550-advanced-269d191a-7493-489c-917f-aafe8434bb38' {   [root@kunpeng42 ~]# awk -F\' '$1=="menuentry " {print i++ " : " $2}' /boot/efi/EFI/centos/grub.cfg 0 : CentOS Linux (4.4.161-1.el7.elrepo.x86_64) 7 (Core) 1 : CentOS Linux (4.20.13-1.el7.elrepo.x86_64) 7 (Core) 2 : CentOS Linux (4.20.12-1.el7.elrepo.x86_64) 7 (Core) 3 : CentOS Linux (3.10.0-957.5.1.el7.x86_64) 7 (Core) 4 : CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core) 5 : CentOS Linux (0-rescue-87e40ba2fda2490c9440fae352527550) 7 (Core)

　　

2，设置默认的启动内核。比如我们选择上边中的CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)这个内核为默认启动。

[root@kunpeng42 ~]# grub2-set-default "CentOS Linux (4.4.161-1.el7.elrepo.x86_64) 7 (Core)" 配置默认内核

验证是否修改成功：

[root@kunpeng42 ~]#  grub2-editenv list
saved_entry=CentOS Linux (4.4.161-1.el7.elrepo.x86_64) 7 (Core)

　　

3，重启机器观察。
重启成功以后查看下机器的内核是不是该内核：

[root@kunpeng42 ~]# uname -r
4.4.161-1.el7.elrepo.x86_64