問題
CentOS 8 yum安裝軟件時，提示無法從AppStream下載
[root@C8-3 ~]# yum -y install httpd mariadb-server mariadb php php-mysql Repository AppStream is listed more than once in the configuration Repository extras is listed more than once in the configuration Repository PowerTools is listed more than once in the configuration Repository centosplus is listed more than once in the configuration Repository fasttrack is listed more than once in the configuration CentOS-8 - AppStream 0.0 B/s | 0 B 00:08 Failed to download metadata for repo 'AppStream' Error: Failed to download metadata for repo 'AppStream' 先排除網絡問題
檢查網通不通，然后確定DNS解析是否正確。
[root@C8-3 ~]# ping baidu.com PING baidu.com (220.181.38.148) 56(84) bytes of data. 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=1 ttl=128 time=12.1 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=2 ttl=128 time=12.2 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=3 ttl=128 time=11.7 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=4 ttl=128 time=13.5 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=5 ttl=128 time=12.2 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=6 ttl=128 time=12.1 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=7 ttl=128 time=13.9 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=8 ttl=128 time=11.4 ms 64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=9 ttl=128 time=13.9 ms ^C --- baidu.com ping statistics --- 9 packets transmitted, 9 received, 0% packet loss, time 31ms rtt min/avg/max/mdev = 11.394/12.554/13.949/0.899 ms 有可能是所在網絡環境在出口封了相應端口，需用其他方式，比如VPN解決。
更換國內yum源
我們無法使用CentOS原生yum源就是因為網絡問題，你懂的。
為了快，更換國內yum源，推薦阿里雲yum或者騰訊yum。網易沒落了。
- 阿里yum源： https://developer.aliyun.com/mirror/centos
- 騰雲yum源： https://mirrors.tencent.com/help/centos.html
[root@C8-3 ~]# mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup.3 [root@C8-3 ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.cloud.tencent.com/repo/centos8_base.repo --2020-11-02 20:51:42-- http://mirrors.cloud.tencent.com/repo/centos8_base.repo Resolving mirrors.cloud.tencent.com (mirrors.cloud.tencent.com)... 111.231.36.190 Connecting to mirrors.cloud.tencent.com (mirrors.cloud.tencent.com)|111.231.36.190|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 1792 (1.8K) [application/octet-stream] Saving to: ‘/etc/yum.repos.d/CentOS-Base.repo’ /etc/yum.repos.d/Ce 100%[==================>] 1.75K --.-KB/s in 0s 2020-11-02 20:51:46 (65.6 MB/s) - ‘/etc/yum.repos.d/CentOS-Base.repo’ saved [1792/1792] 清理之前的yum緩存
[root@C8-3 ~]# yum clean all Repository AppStream is listed more than once in the configuration Repository extras is listed more than once in the configuration Repository PowerTools is listed more than once in the configuration Repository centosplus is listed more than once in the configuration Repository fasttrack is listed more than once in the configuration 18 files removed 建立新的緩存
[root@C8-3 ~]# yum makecache Repository AppStream is listed more than once in the configuration Repository extras is listed more than once in the configuration Repository PowerTools is listed more than once in the configuration Repository centosplus is listed more than once in the configuration Repository fasttrack is listed more than once in the configuration CentOS-8 - AppStream 0.0 B/s | 0 B 00:04 Failed to download metadata for repo 'AppStream' Error: Failed to download metadata for repo 'AppStream' makecache的時候報錯了！
解決makecahe報錯
- Failed to download metadata for repo 'AppStream'
- Error: Failed to download metadata for repo 'AppStream' # 下載meta信息失敗
問題的原因
先看看CentOS7的yum.repos.d
[21:19:17 root@C7-1 ~]#ll /etc/yum.repos.d/ total 44 -rw-r--r--. 1 root root 2523 Oct 27 22:47 CentOS-Base.repo -rw-r--r--. 1 root root 1664 Sep 5 2019 CentOS-Base.repo.bak -rw-r--r--. 1 root root 1309 Sep 5 2019 CentOS-CR.repo -rw-r--r--. 1 root root 649 Sep 5 2019 CentOS-Debuginfo.repo -rw-r--r--. 1 root root 314 Sep 5 2019 CentOS-fasttrack.repo -rw-r--r--. 1 root root 630 Sep 5 2019 CentOS-Media.repo -rw-r--r--. 1 root root 1331 Sep 5 2019 CentOS-Sources.repo -rw-r--r--. 1 root root 6639 Sep 5 2019 CentOS-Vault.repo -rw-r--r--. 1 root root 951 Oct 2 2017 epel.repo -rw-r--r--. 1 root root 1050 Oct 2 2017 epel-testing.repo 再看看CentOS8的yum.repos.d
[root@C8-3 ~]# ll /etc/yum.repos.d/ total 56 -rw-r--r--. 1 root root 815 Oct 28 02:33 CentOS-AppStream.repo -rw-r--r--. 1 root root 1792 Mar 25 2020 CentOS-Base.repo -rw-r--r--. 1 root root 712 Jan 2 2020 CentOS-Base.repo.backup -rw-r--r--. 1 root root 1792 Mar 25 2020 CentOS-Base.repo.backup.3 -rw-r--r--. 1 root root 798 Jan 2 2020 CentOS-centosplus.repo -rw-r--r--. 1 root root 1043 Jan 2 2020 CentOS-CR.repo -rw-r--r--. 1 root root 668 Jan 2 2020 CentOS-Debuginfo.repo -rw-r--r--. 1 root root 756 Jan 2 2020 CentOS-Extras.repo -rw-r--r--. 1 root root 338 Jan 2 2020 CentOS-fasttrack.repo -rw-r--r--. 1 root root 738 Jan 2 2020 CentOS-HA.repo -rw-r--r--. 1 root root 928 Jan 2 2020 CentOS-Media.repo -rw-r--r--. 1 root root 736 Jan 2 2020 CentOS-PowerTools.repo -rw-r--r--. 1 root root 1382 Jan 2 2020 CentOS-Sources.repo -rw-r--r--. 1 root root 74 Jan 2 2020 CentOS-Vault.repo CentOS 8 多了一個 CentOS-AppStream.repo
這是出問題的關鍵。
查看一下CentOS-AppStream.repo
[root@C8-3 ~]# cat /etc/yum.repos.d/CentOS-AppStream.repo.bac # CentOS-AppStream.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [AppStream] name=CentOS-$releasever - AppStream mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=AppStream&infra=$infra baseurl=http://mirror.centos.org/$contentdir/$releasever/AppStream/$basearch/os/ #mirrorlist=http://mirror.centos.org/$contentdir/$releasever/AppStream/$basearch/os/ gpgcheck=1 enabled=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial 解決問題的方法
我們在替換yum源的時候，按照鏡像網站的操作方式，只替換了CentOS-Base.repo。
可是在CentOS8中，CentOS-AppStream.repo的內容沒有更新。
解決方法有兩種
- 直接刪除掉CentOS-AppStream.repo這個文件。（不推薦）
- 將CentOS-AppStream.repo文件中的鏈接更新
解決問題
查看跟新后的CentOS-Base.repo文件
[root@C8-3 ~]# cat /etc/yum.repos.d/CentOS-Base.repo # CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. # # If the mirrorlist= does not work for you, as a fall back you can try the # remarked out baseurl= line instead. # # [BaseOS] name=Qcloud centos OS - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/BaseOS/$basearch/os/ enabled=1 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official [centosplus] name=Qcloud centosplus - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/centosplus/$basearch/os/ enabled=0 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official [extras] name=Qcloud centos extras - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/extras/$basearch/os/ enabled=1 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official [fasttrack] name=Qcloud centos fasttrack - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/fasttrack/$basearch/os/ enabled=0 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official [AppStream] name=Qcloud centos AppStream - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/AppStream/$basearch/os/ enabled=0 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official [PowerTools] name=Qcloud centos PowerTools - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/PowerTools/$basearch/os/ enabled=0 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official 替換更新
- 找到跟新后CentOS-Base.repo中[AppStream]標簽內的內容並復制
[AppStream] name=Qcloud centos AppStream - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/AppStream/$basearch/os/ enabled=0 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official - 打開CentOS-AppStream.repo，注釋掉原有內容，並插入新內容
[root@C8-3 ~]# vim /etc/yum.repos.d/CentOS-AppStream.repo #[AppStream] #name=CentOS-$releasever - AppStream #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=AppStream&infra=$infra #baseurl=http://mirror.centos.org/$contentdir/$releasever/AppStream/$basearch/os/ #mirrorlist=http://mirror.centos.org/$contentdir/$releasever/AppStream/$basearch/os/ #gpgcheck=1 #enabled=1 #pgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial [AppStream] name=Qcloud centos AppStream - $basearch baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/AppStream/$basearch/os/ enabled=0 gpgcheck=1 gpgkey=http://mirrors.cloud.tencent.com/centos/RPM-GPG-KEY-CentOS-Official 我們要養成修改內容時使用注釋而不是刪除的操作方法，用來對比前后差異，出問題了取消掉注釋就可以了。
問題解決
重新運行yum makecache，操作成功
[root@C8-3 ~]# yum makecache Repository AppStream is listed more than once in the configuration Repository extras is listed more than once in the configuration Repository PowerTools is listed more than once in the configuration Repository centosplus is listed more than once in the configuration Repository fasttrack is listed more than once in the configuration Qcloud centos OS - x86_64 119 kB/s | 2.2 MB 00:19 Qcloud centos extras - x86_64 477 B/s | 8.1 kB 00:17 Metadata cache created. 小貼士：
修改文件的良好習慣：
- 先備份需要修改的文件，cp a a.bac
- 在修改文件內容時，添加新內容前，對原內容使用注釋而非刪除