报错：Header V3 RSA_SHA256 Signature, key ID 2f86d6a1_ NOKEY

  博主在CentOS8上dnf安装PHP的依赖包libmcrypt-devel的时候，死活装不上，一直报错。看了下说是依赖项libmcrypt装不上，报错原因说的是是秘钥校验时缺少主机名。这很奇怪，因为用的是阿里的epel源，之前安装各种软件包都没问题，这次突然就秘钥验证不过了。

[root@CentOS8 php-7.3.10]#yum install libmcrypt-devel -y
Last metadata expiration check: 0:01:31 ago on Sat 02 Nov 2019 07:47:12 PM CST.
Dependencies resolved.
=====================================================================================================================================
 Package                             Arch                       Version                             Repository                  Size
=====================================================================================================================================
Installing:
 libmcrypt-devel                     x86_64                     2.5.8-26.el8                        aliyun                      18 k
Installing dependencies:
 libmcrypt                           x86_64                     2.5.8-26.el8                        aliyun                     109 k

Transaction Summary
=====================================================================================================================================
Install  2 Packages

Total size: 127 k
Installed size: 320 k
Downloading Packages:
[SKIPPED] libmcrypt-2.5.8-26.el8.x86_64.rpm: Already downloaded                                                                     
[SKIPPED] libmcrypt-devel-2.5.8-26.el8.x86_64.rpm: Already downloaded                                                               
warning: /var/cache/dnf/aliyun-a19d7e5a690d289a/packages/libmcrypt-2.5.8-26.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 2f86d6a1: NOKEY
aliyun                                                                                               0.0  B/s |   0  B     00:00    
Curl error (3): URL using bad/illegal format or missing URL for file://https://mirrors.aliyun.com/epel/RPM-GPG-KEY-EPEL-8 [Invalid file://hostname/, expected localhost or 127.0.0.1 or none]
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.

  查了下网上很多说法，不过都没有解决疑问。解决方案也五花八门，类似rpm --import /etc/pki/rpm-gpg/RPM*导入秘钥的，也有建议安装时加选项--force --nodeps忽略依赖关系的。秘钥导入没用，我本身yum源仓库配置文件也填写了阿里云镜像源的秘钥路径的。忽略依赖关系强制安装的话，担心会不按依赖项，导致其他别的问题，而且这个选项本身也报错了。
  后来只能干脆把秘钥检查关了，确实能装上了。
  vim /etc/yum.repos.d/aliyun.repo

name=aliyun
baseurl=https://mirrors.aliyun.com/epel/$releasever/Everything/$basearch/
gpgcheck=0
enabled=1
gpgkey=file://https://mirrors.aliyun.com/epel/RPM-GPG-KEY-EPEL-$releasever

  希望不是因为阿里的安装包被人动过而导致秘钥检查不通过吧，姑且相信吧。记录一下，等后期如果有问题或者有空再来排查原因。
  
  
——————————————后记 ———————————–
  原来当时配置yum源文件的时候不小心画蛇添足了，导致gpgkey文件路径不对，应为gpgkey=https://mirrors.aliyun.com/epel/RPM-GPG-KEY-EPEL-$releaseve，用file://的话，就不需要加协议了，直接写主机名或IP加路径。
  要时刻提醒自己还是要仔细，一直不出错不代表没错。
  
                        2019.11.10