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

wget -O /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo

[root@centos7 ~]# cat   /etc/yum.repos.d/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/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$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/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$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/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$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/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$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/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[root@centos7 ~]# cat   /etc/yum.repos.d/epel.repo 
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
baseurl=http://mirrors.aliyun.com/epel/7/$basearch
failovermethod=priority
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
 
[epel-debuginfo]
name=Extra Packages for Enterprise Linux 7 - $basearch - Debug
baseurl=http://mirrors.aliyun.com/epel/7/$basearch/debug
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=0
 
[epel-source]
name=Extra Packages for Enterprise Linux 7 - $basearch - Source
baseurl=http://mirrors.aliyun.com/epel/7/SRPMS
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=0

[root@centos71 ~]#  yum   install   bash-completion
Loaded plugins: fastestmirror
Repository base is listed more than once in the configuration
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
Package 1:bash-completion-2.1-6.el7.noarch already installed and latest version
Nothing to do
[root@centos71 ~]#  yum   install -y   vim   tree   telnet   nc   nmap   net-tools   wget   bash-completion   lrzsz  chrony  bc   net-tools
Loaded plugins: fastestmirror
Repository base is listed more than once in the configuration
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
Package 2:vim-enhanced-7.4.629-6.el7.x86_64 already installed and latest version
Package tree-1.6.0-10.el7.x86_64 already installed and latest version
Package 1:telnet-0.17-64.el7.x86_64 already installed and latest version
Package 2:nmap-ncat-6.40-19.el7.x86_64 already installed and latest version
Package 2:nmap-6.40-19.el7.x86_64 already installed and latest version
Package net-tools-2.0-0.25.20131004git.el7.x86_64 already installed and latest version
Package wget-1.14-18.el7_6.1.x86_64 already installed and latest version
Package 1:bash-completion-2.1-6.el7.noarch already installed and latest version
Package lrzsz-0.12.20-36.el7.x86_64 already installed and latest version
Package chrony-3.4-1.el7.x86_64 already installed and latest version
Package bc-1.06.95-13.el7.x86_64 already installed and latest version
Package net-tools-2.0-0.25.20131004git.el7.x86_64 already installed and latest version
Nothing to do

[root@centos71 ~]# ls /shell_scriprs/ -d
/shell_scriprs/
[root@centos71 ~]# ls  /app/
cmatrix-1.2a  cmatrix-1.2a.tar.gz

[root@centos71 ~]# alias 
alias catnet0=‘cat /etc/sysconfig/network-scripts/ifcfg-eth0‘
alias cp=‘cp -i‘
alias egrep=‘egrep --color=auto‘
alias fgrep=‘fgrep --color=auto‘
alias grep=‘grep --color=auto‘
alias l.=‘ls -d .* --color=auto‘
alias ll=‘ls -l --color=auto‘
alias ls=‘ls --color=auto‘
alias mv=‘mv -i‘
alias rm=‘rm -i‘
alias vinet0=‘vim   /etc/sysconfig/network-scripts/ifcfg-eth0‘
alias which=‘alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde‘

[root@centos71 ~]# cat  /etc/ssh/sshd_config | grep  -i  "dns"
UseDNS no
[root@centos71 ~]# cat  /etc/ssh/sshd_config | grep  -i  "GSSAPIauth"
GSSAPIAuthentication no