安装操作系统时，没有设置IP，安装完成后，设置IP时重启网络报错:
#service network restart
RTNETLINK answers: File exists


检查发现起了 NetworkManager:
#chkconfig --list|grep -i manager
NetworkManager  0:off   1:ff   2:on   3:on   4:on   5:on   6:off



关闭NetworkManager即可:
#chkconfig NetworkManager off
#service NetworkManager stop
#service network restart


但是重启网络后发现没有IP地址:
# ip ad
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:07:e5:89 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::20c:29ff:fe07:e589/64 scope link
       valid_lft forever preferred_lft forever

       
检查发现是因为下面的IPADDR 和 NETMASK手工配置时写成了小写，无法识别到
# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=static
ipaddr=192.168.1.11
netmask=255.255.255.0

改成大小就好了:
IPADDR=192.168.1.11
NETMASK=255.255.255.0


重启网络，识别到IP地址:
#service network restart
# ip ad
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:0c:29:07:e5:89 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.11/24 brd 192.168.1.255 scope global eth0
    inet6 fe80::20c:29ff:fe07:e589/64 scope link
       valid_lft forever preferred_lft forever