下载了Centos7最小化安装后，发现不能上网，ping 和 ifconfig都不能用
1. 先用ip addr来查看ip，发现看不到ip，应该是网卡没有启动
[root@localhost ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:70:22:8a brd ff:ff:ff:ff:ff:ff
2. 进入到网络配置文件目录,找到前面在ip addr中看到的网卡为ens33
[root@localhost ~]# cd /etc/sysconfig/network-scripts
[root@localhost network-scripts]# ls
ifcfg-ens33 ifdown-eth ifdown-post ifdown-Team ifup-aliases ifup-ipv6 ifup-post ifup-Team init.ipv6-global
ifcfg-lo ifdown-ippp ifdown-ppp ifdown-TeamPort ifup-bnep ifup-isdn ifup-ppp ifup-TeamPort network-functions
ifdown ifdown-ipv6 ifdown-routes ifdown-tunnel ifup-eth ifup-plip ifup-routes ifup-tunnel network-functions-ipv6
ifdown-bnep ifdown-isdn ifdown-sit ifup ifup-ippp ifup-plusb ifup-sit ifup-wireless
3. 修改ifcfg-ens33的文件
修改 ONBOOT="yes"，如查不存在ONBOOT创建一个并赋值为"yes"
4. 通过dhcp动态获取IP配置，参考文件
TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="dhcp"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="ens33"
UUID="e4b1323f-5a09-46ce-a121-a51dabc1ee7b"
DEVICE="ens33"
ONBOOT="yes"
5. 配置静态IP，参考文件
TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="static"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="ens33"
UUID="e4b1323f-5a09-46ce-a121-a51dabc1ee7b"
DEVICE="ens33"
ONBOOT="yes"
IPADDR="192.168.31.55" # 静态IP
GATEWAY="192.168.31.1" # 默认网关
NETMASK="255.255.255.0" # 子网掩码
DNS1=192.168.31.1 # DNS 配置
DNS2=114.114.114.114 #
6. 重启网络服务，如果在虚拟机中，无法上网，重启一下
[root@localhost ~] service network restart