CentOS 发布已经很久了，由于本次版本变动比较大，特别是systemd的加入，所以先前一直使用的是centos 6.7版本。今天抽空在虚拟机上安装了CentOS 7，在安装完成后使用 yum update -y 进行系统更新，返回了错误信息：
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Loaded plugins: fastestmirror, priorities, security Setting up Update Process Determining fastest mirrors Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os&infra=stock error was 14: PYCURL ERROR 6 - "Couldn't resolve host 'mirrorlist.centos.org'" Error: Cannot find a valid baseurl for repo: base One of the configured repositories failed (Unknown), and yum doesn't have enough cached data to continue. At this point the only safe thing yum can do is fail. There are a few ways to work "fix" this: 1. Contact the upstream for the repository and get them to fix the problem. 2. Reconfigure the baseurl/etc. for the repository, to point to a working upstream. This is most often useful if you are using a newer distribution release than is supported by the repository (and the packages for the previous distribution release still work). 3. Disable the repository, so yum won't use it by default. Yum will then just ignore the repository until you permanently enable it again or use --enablerepo for temporary usage: yum-config-manager --disable <repoid> 4. Configure the failing repository to be skipped, if it is unavailable. Note that yum will try to contact the repo. when it runs most commands, so will have to try and fail each time (and thus. yum will be be much slower). If it is a very temporary problem though, this is often a nice compromise: yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=true Cannot find a valid baseurl for repo: base/7/x86_64` |
初步判断是网络问题，使用ifconfig查看下网络信息，但是发现：
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-bash: ifconfig: command not found |
ifconfig也不能使用了，Google了下发现ifconfig命令已经被ip命令给取代了。具体ip命令的使用方法如下：
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ip [选项] 操作对象{link|addr|route...} # ip link show # 显示网络接口信息 # ip link set eth0 upi # 开启网卡 # ip link set eth0 down # 关闭网卡 # ip link set eth0 promisc on # 开启网卡的混合模式 # ip link set eth0 promisc offi # 关闭网卡的混个模式 # ip link set eth0 txqueuelen 1200 # 设置网卡队列长度 # ip link set eth0 mtu 1400 # 设置网卡最大传输单元 # ip addr show # 显示网卡IP信息 # ip addr add 192.168.0.1/24 dev eth0 # 设置eth0网卡IP地址192.168.0.1 # ip addr del 192.168.0.1/24 dev eth0 # 删除eth0网卡IP地址 # ip route list # 查看路由信息 # ip route add 192.168.4.0/24 via 192.168.0.254 dev eth0 # 设置192.168.4.0网段的网关为192.168.0.254,数据走eth0接口 # ip route add default via 192.168.0.254 dev eth0 # 设置默认网关为192.168.0.254 # ip route del 192.168.4.0/24 # 删除192.168.4.0网段的网关 # ip route del default # 删除默认路由 |
按照方法，输入了 ip addr ，发现网卡eno16777736并没有IP地址。既然没有ip地址，那直接去/etc/sysconfig/network-scripts目录中看一下的网卡ip信息的配置文件。
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[root@localhost ~]# cd /etc/sysconfig/network-scripts [root@localhost network-scripts]# ll total 196 -rw-r--r--. 1 root root 288 Aug 18 22:36 ifcfg-eno16777736 -rw-r--r--. 1 root root 254 Sep 16 2015 ifcfg-lo lrwxrwxrwx. 1 root root 24 Aug 18 22:48 ifdown -> ../../../usr/sbin/ifdown -rwxr-xr-x. 1 root root 627 Sep 16 2015 ifdown-bnep -rwxr-xr-x. 1 root root 5817 Sep 16 2015 ifdown-eth -rwxr-xr-x. 1 root root 781 Sep 16 2015 ifdown-ippp -rwxr-xr-x. 1 root root 4201 Sep 16 2015 ifdown-ipv6 lrwxrwxrwx. 1 root root 11 Aug 18 22:48 ifdown-isdn -> ifdown-ippp -rwxr-xr-x. 1 root root 1642 Sep 16 2015 ifdown-post -rwxr-xr-x. 1 root root 1068 Sep 16 2015 ifdown-ppp -rwxr-xr-x. 1 root root 837 Sep 16 2015 ifdown-routes -rwxr-xr-x. 1 root root 1444 Sep 16 2015 ifdown-sit -rwxr-xr-x. 1 root root 1462 Sep 16 2015 ifdown-tunnel lrwxrwxrwx. 1 root root 22 Aug 18 22:48 ifup -> ../../../usr/sbin/ifup -rwxr-xr-x. 1 root root 12631 Sep 16 2015 ifup-aliases -rwxr-xr-x. 1 root root 859 Sep 16 2015 ifup-bnep -rwxr-xr-x. 1 root root 11721 Sep 16 2015 ifup-eth -rwxr-xr-x. 1 root root 12039 Sep 16 2015 ifup-ippp -rwxr-xr-x. 1 root root 10430 Sep 16 2015 ifup-ipv6 lrwxrwxrwx. 1 root root 9 Aug 18 22:48 ifup-isdn -> ifup-ippp -rwxr-xr-x. 1 root root 642 Sep 16 2015 ifup-plip -rwxr-xr-x. 1 root root 1043 Sep 16 2015 ifup-plusb -rwxr-xr-x. 1 root root 2609 Sep 16 2015 ifup-post -rwxr-xr-x. 1 root root 4154 Sep 16 2015 ifup-ppp -rwxr-xr-x. 1 root root 1925 Sep 16 2015 ifup-routes -rwxr-xr-x. 1 root root 3263 Sep 16 2015 ifup-sit -rwxr-xr-x. 1 root root 2682 Sep 16 2015 ifup-tunnel -rwxr-xr-x. 1 root root 1740 Sep 16 2015 ifup-wireless -rwxr-xr-x. 1 root root 4623 Sep 16 2015 init.ipv6-global -rw-r--r--. 1 root root 15376 Aug 3 00:15 network-functions -rw-r--r--. 1 root root 26134 Sep 16 2015 network-functions-ipv6 |
可以看到network-scripts目录下面的ifcfg-eth0变成了ifcfg-eno16777736。使用cat命令查看下ifcfg-eno16777736的内容：
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[root@localhost network-scripts]# cat ifcfg-eno16777736 TYPE=Ethernet BOOTPROTO=dhcp DEFROUTE=yes PEERDNS=yes PEERROUTES=yes IPV4_FAILURE_FATAL=no IPV6INIT=yes IPV6_AUTOCONF=yes IPV6_DEFROUTE=yes IPV6_PEERDNS=yes IPV6_PEERROUTES=yes IPV6_FAILURE_FATAL=no NAME=eno16777736 UUID=ba6856dc-abf2-45e4-91d6-581eddab8d61 DEVICE=eno16777736 ONBOOT=no |
从上面的配置中有看到虽然BOOTPROTO=dhcp，但是ONBOOT=no，这里用vi将ONBOOT=no改成ONBOOT=yes，然后重新系统或者重启网络即可：
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systemctl restart network.service |
执行到这里，网络问题就已经解决了，系统可以正常的更新了~
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