本人系统为CentOS 8

可通过 命令 cat /etc/redhat-release 查看自己的系统版本

[root@EasygoingEssential-VM /]# cat /etc/redhat-release
CentOS Linux release 8.0.1905 (Core)

命令 uname -a 可以查看内核版本

[root@EasygoingEssential-VM /]# uname -a
Linux EasygoingEssential-VM 4.18.0-80.11.2.el8_0.x86_64 #1 SMP Tue Sep 24 11:32:19 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

1：更改root原始密码

命令输入 passwd 用户名（不输用户名，表示当前用户），输入两遍密码

[root@EasygoingEssential-VM ~]# passwd
Changing password for user root.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.

2: 安装bash-completion Tab补齐

按Tab建没法补齐命令，所以需要自己安装bash-completion

命令输入 yum -y install bash-completion

[root@EasygoingEssential-VM /]# yum -y install bash-completion

重新登录生效

3: 安装第三方源epel-release，和国内yum源

自己安装的是阿里yum源

1），备份原有源

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

2），下载阿里源

本人系统版本为CentOS-8,所以下载

wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo

或者

curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo

如果其他版本如CentOS-7,则

wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

或者

curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

显示如下：

[root@EasygoingEssential-VM ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-8.repo
--2021-06-15 09:17:20-- https://mirrors.aliyun.com/repo/Centos-8.repo
Resolving mirrors.aliyun.com (mirrors.aliyun.com)... 47.246.22.232, 47.246.22.233, 47.246.22.234, ...
Connecting to mirrors.aliyun.com (mirrors.aliyun.com)|47.246.22.232|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2595 (2.5K) [application/octet-stream]
Saving to: ‘/etc/yum.repos.d/CentOS-Base.repo’
/etc/yum.repos.d/CentO 100%[===========================>] 2.53K --.-KB/s in 0s
2021-06-15 09:17:22 (15.1 MB/s) - ‘/etc/yum.repos.d/CentOS-Base.repo’ saved [2595/2595]

最后清除系统所有的yum缓存

yum clean all 

生成yum缓存

yum makecache 

安装完成！！！！！1

如果没有wget 命令，会提示 -bash: wget: command not found

同样先安装 yum -y install wget即可；

3：安装epel-release

命令：

yum install -y epel-release 

显示如下：

[root@EasygoingEssential-VM ~]# yum install -y epel-release
Repository AppStream is listed more than once in the configuration
Repository extras is listed more than once in the configuration
Repository PowerTools is listed more than once in the configuration
Repository centosplus is listed more than once in the configuration
CentOS-8 - Base - mirrors.aliyun.com 897 kB/s | 2.6 MB 00:02
CentOS-8 - Extras - mirrors.aliyun.com 3.0 kB/s | 9.6 kB 00:03
....
....
Installed:
epel-release-8-8.el8.noarch
Complete!
[root@EasygoingEssential-VM ~]#

安装成功！！！

yum repolist enabled 可查看可用的yum源

yum repolist all 显示所有yum源

显示如下：

[root@EasygoingEssential-VM ~]# yum repolist enabled
Repository AppStream is listed more than once in the configuration
Repository extras is listed more than once in the configuration
Repository PowerTools is listed more than once in the configuration
Repository centosplus is listed more than once in the configuration
Last metadata expiration check: 0:00:18 ago on Tue 15 Jun 2021 09:36:37 AM EDT.
repo id repo name status
AppStream CentOS-8 - AppStream 5,289
base CentOS-8 - Base - mirrors.aliyun.com 1,744
*epel Extra Packages for Enterprise Linux 8 - x86_64 7,437
*epel-modular Extra Packages for Enterprise Linux Modular 8 - x86_64 0
extras CentOS-8 - Extras - mirrors.aliyun.com 34

4：更改ssh端口或者禁用root远程登陆

禁用root前，需要创建一个普通用户及远程登陆密码

useradd slan 创建一个为slan的用户

passwd slan 设置用户slan的密码

显示：

[root@EasygoingEssential-VM ~]# useradd slan
[root@EasygoingEssential-VM ~]# passwd slan
Changing password for user test.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: all authentication tokens updated successfully.
[root@EasygoingEssential-VM ~]#

然后编辑ssh配置文件

vi /etc/ssh/sshd_config

将Port 22 改为 Port 9527(1到65535之间，且没有被占用)，并删掉前面的# 注释符

PermitRootLogin yes 改为 PermitRootLogin no 禁用root远程登陆

大概配置文件如下：

Port 9527
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
```
```xml
#LoginGraceTime 2m
PermitRootLogin no
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

完成，保存重启ssh服务生效。

注: 更改端口一定要关闭防火墙，否则无法用新端口连接ssh.或者自己设置防火墙放行

systemctl stop firewalld.service 关闭防火墙

systemctl disable firewalld.service关闭开机启动

[root@EasygoingEssential-VM ~]# systemctl stop firewalld.service
[root@EasygoingEssential-VM ~]# systemctl disable firewalld.service
Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
Removed /etc/systemd/system/multi-user.target.wants/firewalld.service.

以后ssh登录用创建的slan普通用户登录，登录后可用`su - `切换root用户。

5：更改终端命令行颜色（可选）

更改终端命令行颜色，为了更加直观方便以后观看及查看命令。

更改

vi /etc/profile 此文件对所有用户有效，如果只对当前用户有效，则vi .bashrc

在最后面加上

PS1='[\[\e[32m\]\u\[\e[0m\]\[\e[35m\]@\[\e[0m\]\[\e[33m\]\h\[\e[0m\]\[\e[36m\] \W\[\e[0m\]]\$ '

最后

source /etc/profile 更新文件，可以看到命令行颜色已变化。