（1）ping www.baidu.com [ping: unknown host www.baidu.com]---（2）xshell 连接虚拟机问题---（3） 网卡重启失败

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[root@cdh1 hadoop]# ping www.baidu.com
ping: unknown host www.baidu.com
[root@cdh1 hadoop]# ping 192.138.3.103
PING 192.138.3.103 (192.138.3.103) 56(84) bytes of data.
^C
--- 192.138.3.103 ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 4264ms

[root@cdh1 hadoop]# ping 192.168.3.103
PING 192.168.3.103 (192.168.3.103) 56(84) bytes of data.
64 bytes from 192.168.3.103: icmp_seq=1 ttl=128 time=1.81 ms
64 bytes from 192.168.3.103: icmp_seq=2 ttl=128 time=10.4 ms
64 bytes from 192.168.3.103: icmp_seq=3 ttl=128 time=0.329 ms
64 bytes from 192.168.3.103: icmp_seq=4 ttl=128 time=0.741 ms
64 bytes from 192.168.3.103: icmp_seq=5 ttl=128 time=0.588 ms
64 bytes from 192.168.3.103: icmp_seq=6 ttl=128 time=0.284 ms
64 bytes from 192.168.3.103: icmp_seq=7 ttl=128 time=0.607 ms
64 bytes from 192.168.3.103: icmp_seq=8 ttl=128 time=0.583 ms
^C
--- 192.168.3.103 ping statistics ---
8 packets transmitted, 8 received, 0% packet loss, time 7279ms
rtt min/avg/max/mdev = 0.284/1.923/10.447/3.252 ms
[root@cdh1 hadoop]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:A8:1F:63
inet addr:192.168.3.110  Bcast:192.168.3.255  Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fea8:1f63/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:2393 errors:0 dropped:0 overruns:0 frame:0
TX packets:980 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:203735 (198.9 KiB)  TX bytes:118517 (115.7 KiB)
Interrupt:19 Base address:0x2000

lo        Link encap:Local Loopback
inet addr:127.0.0.1  Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING  MTU:16436  Metric:1
RX packets:5252 errors:0 dropped:0 overruns:0 frame:0
TX packets:5252 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:627383 (612.6 KiB)  TX bytes:627383 (612.6 KiB)

virbr0    Link encap:Ethernet  HWaddr 16:49:39:3D:E6:49
inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b)  TX bytes:4189 (4.0 KiB)

[root@cdh1 hadoop]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0"
HWADDR="00:0C:29:A8:1F:63"
NM_CONTROLLED="yes"
ONBOOT="yes"
BOOTPROTO=static
IPADDR=192.168.3.110
NETMASK=255.255.255.0
GATEWAY=192.168.3.1
[root@cdh1 hadoop]# cat /etc/resolv.conf
# Generated by NetworkManager

# No nameservers found; try putting DNS servers into your
# ifcfg files in /etc/sysconfig/network-scripts like so:
#
# DNS1=xxx.xxx.xxx.xxx
# DNS2=xxx.xxx.xxx.xxx
# DOMAIN=lab.foo.com bar.foo.com
[root@cdh1 hadoop]# vim /etc/resolv.conf
[root@cdh1 hadoop]# cat /etc/resolv.conf
# Generated by NetworkManager

# No nameservers found; try putting DNS servers into your
# ifcfg files in /etc/sysconfig/network-scripts like so:
#
# DNS1=xxx.xxx.xxx.xxx
# DNS2=xxx.xxx.xxx.xxx
# DOMAIN=lab.foo.com bar.foo.com

nameserver 8.8.8.8
nameserver 114.114.114.114
[root@cdh1 hadoop]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0"
HWADDR="00:0C:29:A8:1F:63"
NM_CONTROLLED="yes"
ONBOOT="yes"
BOOTPROTO=static
IPADDR=192.168.3.110
NETMASK=255.255.255.0
GATEWAY=192.168.3.1
[root@cdh1 hadoop]# vim /etc/sysconfig/network-scripts/ifcfg-eth0
[root@cdh1 hadoop]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0"
HWADDR="00:0C:29:A8:1F:63"
NM_CONTROLLED="yes"
ONBOOT="yes"
BOOTPROTO=static
IPADDR=192.168.3.110
NETMASK=255.255.255.0
GATEWAY=192.168.3.1
DNS2=114.114.114.114
DNS1=8.8.8.8
[root@cdh1 hadoop]# ping www.baidu.com
PING www.a.shifen.com (119.75.218.70) 56(84) bytes of data.
64 bytes from 119.75.218.70: icmp_seq=1 ttl=56 time=7.79 ms
64 bytes from 119.75.218.70: icmp_seq=2 ttl=56 time=8.07 ms
64 bytes from 119.75.218.70: icmp_seq=3 ttl=56 time=7.30 ms
64 bytes from 119.75.218.70: icmp_seq=4 ttl=56 time=9.77 ms
64 bytes from 119.75.218.70: icmp_seq=5 ttl=56 time=8.49 ms
64 bytes from 119.75.218.70: icmp_seq=6 ttl=56 time=14.9 ms
64 bytes from 119.75.218.70: icmp_seq=7 ttl=56 time=9.98 ms
64 bytes from 119.75.218.70: icmp_seq=8 ttl=56 time=9.09 ms
64 bytes from 119.75.218.70: icmp_seq=9 ttl=56 time=11.0 ms
64 bytes from 119.75.218.70: icmp_seq=10 ttl=56 time=28.3 ms
64 bytes from 119.75.218.70: icmp_seq=11 ttl=56 time=5.94 ms
64 bytes from 119.75.218.70: icmp_seq=12 ttl=56 time=5.62 ms
^C
--- www.a.shifen.com ping statistics ---
12 packets transmitted, 12 received, 0% packet loss, time 21194ms
rtt min/avg/max/mdev = 5.621/10.534/28.306/5.859 ms
[root@cdh1 hadoop]#
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SSH error:a public key file has not been specified by this session
xshell 连接失败   /etc/ssh/sshd_config的PasswordAuthentication项为yes，重启服务（service sshd restart）