centos7 设置默认启动kernel，删除其他版本kernel_--kernelsourcedir

使用cat /boot/grub2/grub.cfg |grep menuentry 查看系统可用内核

    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 (3.10.0-514.16.1.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-6f5840d0-55ac-4d3b-899b-61c0297c5347' {
    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-6f5840d0-55ac-4d3b-899b-61c0297c5347' {
    menuentry 'CentOS Linux (0-rescue-d57307c454c0437d91c309347178cdf5) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-d57307c454c0437d91c309347178cdf5-advanced-6f5840d0-55ac-4d3b-899b-61c0297c5347' {
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查看当前内核

    [root@bigapp-slave27 ~]# uname -r
    3.10.0-514.16.1.el7.x86_64
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修改开机时默认使用的内核

    grub2-set-default 'CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)'
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查看内核修改结果

    [root@bigapp-slave27 ~]# grub2-editenv list
    saved_entry=CentOS Linux (3.10.0-327.el7.x86_64) 7 (Core)
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查看系统安装了哪些内核包

    [root@bigapp-slave27 ~]# rpm -qa |grep kernel
    kernel-3.10.0-327.el7.x86_64
    kernel-headers-3.10.0-514.6.1.el7.x86_64
    kernel-tools-libs-3.10.0-327.el7.x86_64
    kernel-3.10.0-514.16.1.el7.x86_64
    kernel-tools-3.10.0-327.el7.x86_64
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使用yum remove 或rpm -e 删除无用内核

    yum remove kernel-3.10.0-327.el7.x86_64
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