[LINUX] yum 명령어가 실행되지 않을 때 Could not resolve host .. 해결하기

yum 명령어를 사용 시, 아래와 같은 오류가 뜨면서 yum 이 수행되지 않은 때 해결 방법입니다.

Loaded plugins: fastestmirror, langpacks
Determining fastest mirrors
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; 알 수 없는 오류"


 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. Run the command with the repository temporarily disabled
            yum --disablerepo=<repoid> ...

     4. Disable the repository permanently, 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>
        or
            subscription-manager repos --disable=<repoid>

     5. 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

1. route 명령어로 게이트웨이가 제대로 설정되어 있는지 확인합니다.

# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         gateway         0.0.0.0         UG    100    0        0 enp7s0
192.168.0.0     0.0.0.0         255.255.255.0   U     100    0        0 enp7s0
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
gateway         0.0.0.0         255.255.255.255 UH    100    0        0 enp7s0

제대로 설정되어 있지 않은경우 게이트웨이 값을 설정한 뒤 네트워크를 재시작 합니다.     

# cat /etc/sysconfig/network
# Created by anaconda
GATEWAY=192.168.0.1

# service network restart
Restarting network (via systemctl):                        [  OK  ]

2. nslookup 명령어로 설정된 DNS 가 제대로 설정되어 있는지 확인합니다.

# nslookup
> server
Default server: 127.0.0.1
Address: 127.0.0.1#53
Default server: 168.126.63.1
Address: 168.126.63.1#53
Default server: 168.126.63.2
Address: 168.126.63.2#53
> exit

제대로 설정되어 있지 않은경우 DNS 값을 설정합니다. 이 때 설정값은 1 개 이상이 될 수 있습니다.

# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 127.0.0.1
nameserver 168.126.63.1
nameserver 168.126.63.2

3. /etc/sysconfig/network-scripts/ifcfg-[이더넷명] 의 프로퍼티 값을 확인합니다.

     GATEWAY, DNS, IPADDR, ONBOOT 등등의 설정값을 확인한 뒤 위에서 설정한 값과 동일하게 설정합니다.

# vi /etc/sysconfig/network-scripts/ifcfg-enp7s0

DEVICE="enp7s0"
ONBOOT="yes"
IPADDR="192.168.0.50"
PREFIX="24"
GATEWAY="192.168.0.1"
DNS1="168.126.63.1"

4. 외부 아이피로 핑을 날려봅니다.

# ping 8.8.8.8          # google
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=56 time=30.9 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=56 time=30.1 ms
--- 8.8.8.8 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 30.194/30.581/30.968/0.387 ms

5. 핑이 제대로 날라가면 yum 명령어를 다시 수행합니다.

   yum 명령어가 적용되는 것을 확인할 수 있습니다.

# yum search cmake
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base: data.nicehosting.co.kr
 * extras: data.nicehosting.co.kr
 * updates: data.nicehosting.co.kr
base                                                                                                                                                                                                                  | 3.6 kB  00:00:00
extras                                                                                                                                                                                                                | 3.4 kB  00:00:00
updates                                                                                                                                                                                                               | 3.4 kB  00:00:00
(1/4): base/7/x86_64/primary_db                                                                                                                                                                                       | 5.9 MB  00:00:00
(2/4): extras/7/x86_64/primary_db                                                                                                                                                                                     | 147 kB  00:00:02
(3/4): base/7/x86_64/group_gz                                                                                                                                                                                         | 166 kB  00:00:03
(4/4): updates/7/x86_64/primary_db                                                                                                                                                                                    | 2.0 MB  00:00:18
============================================================================================================ N/S matched: cmake =============================================================================================================
cmake-gui.x86_64 : Qt GUI for cmake
cmake.x86_64 : Cross-platform make system

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