Centos系统的升级

文章来源：https://blog.csdn.net/kikajack/article/details/79396793

系统及内核版本：

 [root@node5 ~]# cat /etc/redhat-release
 CentOS Linux release 7.3. (Core)

 [root@node5 ~]# uname -a
 Linux node6 3.10.-.el7.x86_64 # SMP Tue Nov  :: UTC  x86_64 x86_64 x86_64 GNU/Linux

更新仓库：

 [root@node5 yum.repos.d]# yum update

 [root@node5 yum.repos.d]# cat /etc/redhat-release
 CentOS Linux release 7.7. (Core)

更新内核：

启用Elrepo仓库

 [root@node5 ~]#  rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

 [root@node5 ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm

查看可用系统内核包

 [root@node5 ~]# yum --disablerepo="*" --enablerepo="elrepo-kernel" list available
 已加载插件：fastestmirror, langpacks
 Loading mirror speeds from cached hostfile
  * elrepo-kernel: hkg.mirror.rackspace.com
 elrepo-kernel                                           | 2.9 kB     :
 elrepo-kernel/primary_db                                  | 1.8 MB   :
 可安装的软件包
 kernel-lt.x86_64                       4.4.-.el7.elrepo       elrepo-kernel
 kernel-lt-devel.x86_64                 4.4.-.el7.elrepo       elrepo-kernel
 kernel-lt-doc.noarch                   4.4.-.el7.elrepo       elrepo-kernel
 kernel-lt-headers.x86_64               4.4.-.el7.elrepo       elrepo-kernel
 kernel-lt-tools.x86_64                 4.4.-.el7.elrepo       elrepo-kernel
 kernel-lt-tools-libs.x86_64            4.4.-.el7.elrepo       elrepo-kernel
 kernel-lt-tools-libs-devel.x86_64      4.4.-.el7.elrepo       elrepo-kernel
 kernel-ml.x86_64                       5.3.-.el7.elrepo         elrepo-kernel
 kernel-ml-devel.x86_64                 5.3.-.el7.elrepo         elrepo-kernel
 kernel-ml-doc.noarch                   5.3.-.el7.elrepo         elrepo-kernel
 kernel-ml-headers.x86_64               5.3.-.el7.elrepo         elrepo-kernel
 kernel-ml-tools.x86_64                 5.3.-.el7.elrepo         elrepo-kernel
 kernel-ml-tools-libs.x86_64            5.3.-.el7.elrepo         elrepo-kernel
 kernel-ml-tools-libs-devel.x86_64      5.3.-.el7.elrepo         elrepo-kernel
 perf.x86_64                            5.3.-.el7.elrepo         elrepo-kernel
 python-perf.x86_64                     5.3.-.el7.elrepo         elrepo-kernel

安装最新内核

 [root@node5 ~]# yum --enablerepo=elrepo-kernel install kernel-ml

查看系统上可用的所有内核：

 [root@node5 ~]# awk -F\' '$=="menuentry " {print i++ " : " $}' /etc/grub2.cfg
  : CentOS Linux (5.3.-.el7.elrepo.x86_64)  (Core)
  : CentOS Linux (3.10.-.el7.x86_64)  (Core)
  : CentOS Linux (3.10.-.el7.x86_64)  (Core)
  : CentOS Linux (-rescue-ca186cba450446219a27ee86e037534b)  (Core)

设置默认启动选项grub(多系统启动程序)，有两种方法：

通过 grub2-set-default 0 命令设置，0为上步执行结果

通过编辑文/etc/default/grub，将GRUB_DEFAULT=saved改为GRUB_DEFAULT=0

通过 gurb2-mkconfig 命令创建 grub2 的配置文件：

 [root@node5 ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
 Generating grub configuration file ...
 Found linux image: /boot/vmlinuz-5.3.-.el7.elrepo.x86_64
 Found initrd image: /boot/initramfs-5.3.-.el7.elrepo.x86_64.img
 Found linux image: /boot/vmlinuz-3.10.-.el7.x86_64
 Found initrd image: /boot/initramfs-3.10.-.el7.x86_64.img
 Found linux image: /boot/vmlinuz-3.10.-.el7.x86_64
 Found initrd image: /boot/initramfs-3.10.-.el7.x86_64.img
 Found linux image: /boot/vmlinuz--rescue-ca186cba450446219a27ee86e037534b
 Found initrd image: /boot/initramfs--rescue-ca186cba450446219a27ee86e037534b.img

重启系统查看：

 [root@node5 ~]# reboot
 [root@node5 ~]# uname -r
 5.3.-.el7.elrepo.x86_64

可以选择删除其余旧版本内核，若系统需要降级亦可保留其他内核

删除旧版本内核可用yum remove 或者 yum-utils:

用rpm -qa | grep kernal 得到内核列表，再用yum remove 删除

 [root@node5 ~]# rpm -qa | grep kernel
 kernel-tools-libs-3.10.-.el7.x86_64
 kernel-3.10.-.el7.x86_64
 kernel-tools-3.10.-.el7.x86_64
 abrt-addon-kerneloops-2.1.-.el7.centos.x86_64
 kernel-ml-5.3.-.el7.elrepo.x86_64
 kernel-3.10.-.el7.x86_64

yum-utils 在系统安装超过三个内核时会删除旧版本内核

[root@node5 ~]# package-cleanup --oldkernels
已加载插件：fastestmirror, langpacks
No old kernels to remove

安装指定版本内核时只需在install后面加上指定版本即可。