一、修改yum源

查看现有系统内核版本：

备份系统自带的yum源：

一、修改CentOS-Base.repo
## cat CentOS-Base.repo 
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#
 
[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#released updates 
[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7


二、修改CentOS-CR.repo
## cat CentOS-CR.repo
# CentOS-CR.repo
#
# The Continuous Release ( CR )  repository contains rpms that are due in the next
# release for a specific CentOS Version ( eg. next release in CentOS-7 ); these rpms
# are far less tested, with no integration checking or update path testing having
# taken place. They are still built from the upstream sources, but might not map 
# to an exact upstream distro release.
#
# These packages are made available soon after they are built, for people willing 
# to test their environments, provide feedback on content for the next release, and
# for people looking for early-access to next release content.
#
# The CR repo is shipped in a disabled state by default; its important that users 
# understand the implications of turning this on. 
#
# NOTE: We do not use a mirrorlist for the CR repos, to ensure content is available
#       to everyone as soon as possible, and not need to wait for the external
#       mirror network to seed first. However, many local mirrors will carry CR repos
#       and if desired you can use one of these local mirrors by editing the baseurl
#       line in the repo config below.
#

[cr]
name=CentOS-$releasever - cr
baseurl=http://mirror.centos.org/centos/$releasever/cr/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0


三、修改CentOS-Debuginfo.repo
### cat CentOS-Debuginfo.repo
# CentOS-Debug.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#

# All debug packages from all the various CentOS-7 releases
# are merged into a single repo, split by BaseArch
#
# Note: packages in the debuginfo repo are currently not signed
#

[base-debuginfo]
name=CentOS-7 - Debuginfo
baseurl=http://debuginfo.centos.org/7/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-Debug-7
enabled=0


四、修改CentOS-fasttrack.repo
## cat CentOS-fasttrack.repo
#CentOS-fasttrack.repo

[fasttrack]
name=CentOS-7 - fasttrack
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=fasttrack&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/fasttrack/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7


五、修改CentOS-Media.repo
## cat CentOS-Media.repo
# CentOS-Media.repo
#
#  This repo can be used with mounted DVD media, verify the mount point for
#  CentOS-7.  You can use this repo and yum to install items directly off the
#  DVD ISO that we release.
#
# To use this repo, put in your DVD and use it with the other repos too:
#  yum --enablerepo=c7-media [command]
#  
# or for ONLY the media repo, do this:
#
#  yum --disablerepo=\* --enablerepo=c7-media [command]

[c7-media]
name=CentOS-$releasever - Media
baseurl=file:///media/CentOS/
        file:///media/cdrom/
        file:///media/cdrecorder/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7


六、修改CentOS-Sources.repo
### cat CentOS-Sources.repo
# CentOS-Sources.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#

[base-source]
name=CentOS-$releasever - Base Sources
baseurl=http://vault.centos.org/centos/$releasever/os/Source/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#released updates 
[updates-source]
name=CentOS-$releasever - Updates Sources
baseurl=http://vault.centos.org/centos/$releasever/updates/Source/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras-source]
name=CentOS-$releasever - Extras Sources
baseurl=http://vault.centos.org/centos/$releasever/extras/Source/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus-source]
name=CentOS-$releasever - Plus Sources
baseurl=http://vault.centos.org/centos/$releasever/centosplus/Source/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7


# cat CentOS-Vault.repo
# CentOS Vault contains rpms from older releases in the CentOS-7
# tree.

# C7.0.1406
[C7.0.1406-base]
name=CentOS-7.0.1406 - Base
baseurl=http://vault.centos.org/7.0.1406/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.0.1406-updates]
name=CentOS-7.0.1406 - Updates
baseurl=http://vault.centos.org/7.0.1406/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.0.1406-extras]
name=CentOS-7.0.1406 - Extras
baseurl=http://vault.centos.org/7.0.1406/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.0.1406-centosplus]
name=CentOS-7.0.1406 - CentOSPlus
baseurl=http://vault.centos.org/7.0.1406/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.0.1406-fasttrack]
name=CentOS-7.0.1406 - Fasttrack
baseurl=http://vault.centos.org/7.0.1406/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.1.1503
[C7.1.1503-base]
name=CentOS-7.1.1503 - Base
baseurl=http://vault.centos.org/7.1.1503/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.1.1503-updates]
name=CentOS-7.1.1503 - Updates
baseurl=http://vault.centos.org/7.1.1503/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.1.1503-extras]
name=CentOS-7.1.1503 - Extras
baseurl=http://vault.centos.org/7.1.1503/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.1.1503-centosplus]
name=CentOS-7.1.1503 - CentOSPlus
baseurl=http://vault.centos.org/7.1.1503/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.1.1503-fasttrack]
name=CentOS-7.1.1503 - Fasttrack
baseurl=http://vault.centos.org/7.1.1503/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.2.1511
[C7.2.1511-base]
name=CentOS-7.2.1511 - Base
baseurl=http://vault.centos.org/7.2.1511/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.2.1511-updates]
name=CentOS-7.2.1511 - Updates
baseurl=http://vault.centos.org/7.2.1511/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.2.1511-extras]
name=CentOS-7.2.1511 - Extras
baseurl=http://vault.centos.org/7.2.1511/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.2.1511-centosplus]
name=CentOS-7.2.1511 - CentOSPlus
baseurl=http://vault.centos.org/7.2.1511/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.2.1511-fasttrack]
name=CentOS-7.2.1511 - Fasttrack
baseurl=http://vault.centos.org/7.2.1511/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.3.1611
[C7.3.1611-base]
name=CentOS-7.3.1611 - Base
baseurl=http://vault.centos.org/7.3.1611/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.3.1611-updates]
name=CentOS-7.3.1611 - Updates
baseurl=http://vault.centos.org/7.3.1611/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.3.1611-extras]
name=CentOS-7.3.1611 - Extras
baseurl=http://vault.centos.org/7.3.1611/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.3.1611-centosplus]
name=CentOS-7.3.1611 - CentOSPlus
baseurl=http://vault.centos.org/7.3.1611/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.3.1611-fasttrack]
name=CentOS-7.3.1611 - Fasttrack
baseurl=http://vault.centos.org/7.3.1611/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.4.1708
[C7.4.1708-base]
name=CentOS-7.4.1708 - Base
baseurl=http://vault.centos.org/7.4.1708/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.4.1708-updates]
name=CentOS-7.4.1708 - Updates
baseurl=http://vault.centos.org/7.4.1708/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.4.1708-extras]
name=CentOS-7.4.1708 - Extras
baseurl=http://vault.centos.org/7.4.1708/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.4.1708-centosplus]
name=CentOS-7.4.1708 - CentOSPlus
baseurl=http://vault.centos.org/7.4.1708/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.4.1708-fasttrack]
name=CentOS-7.4.1708 - Fasttrack
baseurl=http://vault.centos.org/7.4.1708/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.5.1804
[C7.5.1804-base]
name=CentOS-7.5.1804 - Base
baseurl=http://vault.centos.org/7.5.1804/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.5.1804-updates]
name=CentOS-7.5.1804 - Updates
baseurl=http://vault.centos.org/7.5.1804/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.5.1804-extras]
name=CentOS-7.5.1804 - Extras
baseurl=http://vault.centos.org/7.5.1804/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.5.1804-centosplus]
name=CentOS-7.5.1804 - CentOSPlus
baseurl=http://vault.centos.org/7.5.1804/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.5.1804-fasttrack]
name=CentOS-7.5.1804 - Fasttrack
baseurl=http://vault.centos.org/7.5.1804/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.6.1810
[C7.6.1810-base]
name=CentOS-7.6.1810 - Base
baseurl=http://vault.centos.org/7.6.1810/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.6.1810-updates]
name=CentOS-7.6.1810 - Updates
baseurl=http://vault.centos.org/7.6.1810/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.6.1810-extras]
name=CentOS-7.6.1810 - Extras
baseurl=http://vault.centos.org/7.6.1810/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.6.1810-centosplus]
name=CentOS-7.6.1810 - CentOSPlus
baseurl=http://vault.centos.org/7.6.1810/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.6.1810-fasttrack]
name=CentOS-7.6.1810 - Fasttrack
baseurl=http://vault.centos.org/7.6.1810/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.7.1908
[C7.7.1908-base]
name=CentOS-7.7.1908 - Base
baseurl=http://vault.centos.org/7.7.1908/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.7.1908-updates]
name=CentOS-7.7.1908 - Updates
baseurl=http://vault.centos.org/7.7.1908/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.7.1908-extras]
name=CentOS-7.7.1908 - Extras
baseurl=http://vault.centos.org/7.7.1908/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.7.1908-centosplus]
name=CentOS-7.7.1908 - CentOSPlus
baseurl=http://vault.centos.org/7.7.1908/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.7.1908-fasttrack]
name=CentOS-7.7.1908 - Fasttrack
baseurl=http://vault.centos.org/7.7.1908/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.8.2003
[C7.8.2003-base]
name=CentOS-7.8.2003 - Base
baseurl=http://vault.centos.org/7.8.2003/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.8.2003-updates]
name=CentOS-7.8.2003 - Updates
baseurl=http://vault.centos.org/7.8.2003/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.8.2003-extras]
name=CentOS-7.8.2003 - Extras
baseurl=http://vault.centos.org/7.8.2003/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.8.2003-centosplus]
name=CentOS-7.8.2003 - CentOSPlus
baseurl=http://vault.centos.org/7.8.2003/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.8.2003-fasttrack]
name=CentOS-7.8.2003 - Fasttrack
baseurl=http://vault.centos.org/7.8.2003/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

# C7.9.2009
[C7.9.2009-base]
name=CentOS-7.9.2009 - Base
baseurl=http://vault.centos.org/7.9.2009/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.9.2009-updates]
name=CentOS-7.9.2009 - Updates
baseurl=http://vault.centos.org/7.9.2009/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.9.2009-extras]
name=CentOS-7.9.2009 - Extras
baseurl=http://vault.centos.org/7.9.2009/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.9.2009-centosplus]
name=CentOS-7.9.2009 - CentOSPlus
baseurl=http://vault.centos.org/7.9.2009/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

[C7.9.2009-fasttrack]
name=CentOS-7.9.2009 - Fasttrack
baseurl=http://vault.centos.org/7.9.2009/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=0

七、修改CentOS-x86_64-kernel.repo
### cat CentOS-x86_64-kernel.repo
[centos-kernel]
name=CentOS LTS Kernels for $basearch
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=kernel&infra=$infra
#baseurl=http://mirror.centos.org/altarch/7/kernel/$basearch/
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

[centos-kernel-experimental]
name=CentOS Experimental Kernels for $basearch
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=experimental&infra=$infra
#baseurl=http://mirror.centos.org/altarch/7/experimental/$basearch/
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7


八、添加内核源
## # cat repo.repo 
[elrepo]
name=elrepo
baseurl=https://mirrors.aliyun.com/elrepo/archive/kernel/el7/x86_64
gpgcheck=0
enabled=1

修改dns：

二、查看仓库中的内核包

# yum clean all && yum makecache


# yum list --showduplicate kernel*

三、内核升级

# yum install kernel-lt-5.4.278 -y

# yum install kernel-lt-devel-5.4.278 -y

四、设置启动的内核

设置编码为0的内核，也就是刚刚安装的内核：
# grub2-set-default 0

五、重启

# reboot

六、查看生效版本