有时候在使用YUM的时候，你会出现如题所示的问题，具体如下：
[root@mha1 c++]# yum install -y glib2-devel libpcap-devel libnet-devel Loaded plugins: fastestmirror, refresh-packagekit, security Determining fastest mirrors * extras: mirrors.163.com * remi-safe: mirrors.thzhost.com * updates: mirrors.aliyun.com LocalPercona | 2.9 kB 00:00 ... LocalPercona/primary_db | 16 kB 00:00 ... http://download.fedoraproject.org/pub/epel/6/x86_64/repodata/repomd.xml: [Errno 14] problem making ssl connection Trying other mirror. Error: Cannot retrieve repository metadata (repomd.xml) for repository: epel. Please verify its path and try again [root@mha1 c++]#
对于该问题，需要首先禁用出问题的YUM源（enabled=0），然后安装ca-certificates包：
yum install ca-certificates
可以看到，上面出问题的是EPEL源。
先禁用：
[root@mha1 ~]# cat /etc/yum.repos.d/epel.repo [epel] name=Extra Packages for Enterprise Linux 6 - $basearch baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch failovermethod=priority enabled=0 gpgcheck=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 [epel-debuginfo] name=Extra Packages for Enterprise Linux 6 - $basearch - Debug baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch/debug #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-6&arch=$basearch failovermethod=priority enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 gpgcheck=0 [epel-source] name=Extra Packages for Enterprise Linux 6 - $basearch - Source baseurl=http://download.fedoraproject.org/pub/epel/6/SRPMS #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-source-6&arch=$basearch failovermethod=priority enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 gpgcheck=0 [root@mha1 ~]#
然后，安装软件包：
[root@mha1 ~]# yum install ca-certificates Loaded plugins: fastestmirror, refresh-packagekit, security Loading mirror speeds from cached hostfile * base: mirrors.btte.net * extras: mirrors.163.com * remi-safe: mirrors.tuna.tsinghua.edu.cn * updates: mirrors.aliyun.com extras | 3.4 kB 00:00 updates | 3.4 kB 00:00 Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package ca-certificates.noarch 0:2010.63-3.el6_1.5 will be updated ---> Package ca-certificates.noarch 0:2015.2.6-65.0.1.el6_7 will be an update --> Processing Dependency: p11-kit-trust >= 0.18.4-2 for package: ca-certificates-2015.2.6-65.0.1.el6_7.noarch --> Processing Dependency: p11-kit >= 0.18.4-2 for package: ca-certificates-2015.2.6-65.0.1.el6_7.noarch --> Running transaction check ---> Package p11-kit.x86_64 0:0.18.5-2.el6_5.2 will be installed ---> Package p11-kit-trust.x86_64 0:0.18.5-2.el6_5.2 will be installed --> Processing Conflict: p11-kit-trust-0.18.5-2.el6_5.2.x86_64 conflicts nss < 3.14.3-33 --> Restarting Dependency Resolution with new changes. --> Running transaction check ---> Package nss.x86_64 0:3.13.3-6.el6 will be updated --> Processing Dependency: nss = 3.13.3-6.el6 for package: nss-tools-3.13.3-6.el6.x86_64 --> Processing Dependency: nss = 3.13.3-6.el6 for package: nss-sysinit-3.13.3-6.el6.x86_64 ---> Package nss.x86_64 0:3.21.3-2.el6_8 will be an update --> Processing Dependency: nss-util >= 3.21.0 for package: nss-3.21.3-2.el6_8.x86_64 --> Processing Dependency: nss-softokn(x86-64) >= 3.14.3-22 for package: nss-3.21.3-2.el6_8.x86_64 --> Processing Dependency: nspr >= 4.11.0 for package: nss-3.21.3-2.el6_8.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.21)(64bit) for package: nss-3.21.3-2.el6_8.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.17.1)(64bit) for package: nss-3.21.3-2.el6_8.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.15)(64bit) for package: nss-3.21.3-2.el6_8.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.14)(64bit) for package: nss-3.21.3-2.el6_8.x86_64 --> Running transaction check ---> Package nspr.x86_64 0:4.9-1.el6 will be updated ---> Package nspr.x86_64 0:4.11.0-1.el6 will be an update ---> Package nss-softokn.x86_64 0:3.12.9-11.el6 will be updated ---> Package nss-softokn.x86_64 0:3.14.3-23.3.el6_8 will be an update --> Processing Dependency: nss-softokn-freebl(x86-64) >= 3.14.3-23.3.el6_8 for package: nss-softokn-3.14.3-23.3.el6_8.x86_64 ---> Package nss-sysinit.x86_64 0:3.13.3-6.el6 will be updated ---> Package nss-sysinit.x86_64 0:3.21.3-2.el6_8 will be an update ---> Package nss-tools.x86_64 0:3.13.3-6.el6 will be updated ---> Package nss-tools.x86_64 0:3.21.3-2.el6_8 will be an update ---> Package nss-util.x86_64 0:3.13.3-2.el6 will be updated ---> Package nss-util.x86_64 0:3.21.3-1.el6_8 will be an update --> Running transaction check ---> Package nss-softokn-freebl.x86_64 0:3.12.9-11.el6 will be updated ---> Package nss-softokn-freebl.x86_64 0:3.14.3-23.3.el6_8 will be an update --> Finished Dependency Resolution Dependencies Resolved ================================================================================================================================================== Package Arch Version Repository Size ================================================================================================================================================== Updating: ca-certificates noarch 2015.2.6-65.0.1.el6_7 base 1.2 M nss x86_64 3.21.3-2.el6_8 updates 859 k Installing for dependencies: p11-kit x86_64 0.18.5-2.el6_5.2 base 94 k p11-kit-trust x86_64 0.18.5-2.el6_5.2 base 71 k Updating for dependencies: nspr x86_64 4.11.0-1.el6 base 114 k nss-softokn x86_64 3.14.3-23.3.el6_8 updates 262 k nss-softokn-freebl x86_64 3.14.3-23.3.el6_8 updates 168 k nss-sysinit x86_64 3.21.3-2.el6_8 updates 47 k nss-tools x86_64 3.21.3-2.el6_8 updates 437 k nss-util x86_64 3.21.3-1.el6_8 updates 67 k Transaction Summary ================================================================================================================================================== Install 2 Package(s) Upgrade 8 Package(s) Total download size: 3.3 M Is this ok [y/N]: y Downloading Packages: (1/10): ca-certificates-2015.2.6-65.0.1.el6_7.noarch.rpm | 1.2 MB 00:02 (2/10): nspr-4.11.0-1.el6.x86_64.rpm | 114 kB 00:00 (3/10): nss-3.21.3-2.el6_8.x86_64.rpm | 859 kB 00:01 (4/10): nss-softokn-3.14.3-23.3.el6_8.x86_64.rpm | 262 kB 00:00 (5/10): nss-softokn-freebl-3.14.3-23.3.el6_8.x86_64.rpm | 168 kB 00:00 (6/10): nss-sysinit-3.21.3-2.el6_8.x86_64.rpm | 47 kB 00:00 (7/10): nss-tools-3.21.3-2.el6_8.x86_64.rpm | 437 kB 00:00 (8/10): nss-util-3.21.3-1.el6_8.x86_64.rpm | 67 kB 00:00 (9/10): p11-kit-0.18.5-2.el6_5.2.x86_64.rpm | 94 kB 00:00 (10/10): p11-kit-trust-0.18.5-2.el6_5.2.x86_64.rpm | 71 kB 00:00 -------------------------------------------------------------------------------------------------------------------------------------------------- Total 439 kB/s | 3.3 MB 00:07 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Updating : nspr-4.11.0-1.el6.x86_64 1/18 Updating : nss-util-3.21.3-1.el6_8.x86_64 2/18 Updating : nss-softokn-freebl-3.14.3-23.3.el6_8.x86_64 3/18 Installing : p11-kit-0.18.5-2.el6_5.2.x86_64 4/18 Updating : nss-softokn-3.14.3-23.3.el6_8.x86_64 5/18 Updating : nss-sysinit-3.21.3-2.el6_8.x86_64 6/18 Updating : nss-3.21.3-2.el6_8.x86_64 7/18 Installing : p11-kit-trust-0.18.5-2.el6_5.2.x86_64 8/18 Updating : ca-certificates-2015.2.6-65.0.1.el6_7.noarch 9/18 Updating : nss-tools-3.21.3-2.el6_8.x86_64 10/18 Cleanup : nss-tools-3.13.3-6.el6.x86_64 11/18 Cleanup : ca-certificates-2010.63-3.el6_1.5.noarch 12/18 Cleanup : nss-sysinit-3.13.3-6.el6.x86_64 13/18 Cleanup : nss-3.13.3-6.el6.x86_64 14/18 Cleanup : nss-softokn-3.12.9-11.el6.x86_64 15/18 Cleanup : nss-util-3.13.3-2.el6.x86_64 16/18 Cleanup : nspr-4.9-1.el6.x86_64 17/18 Cleanup : nss-softokn-freebl-3.12.9-11.el6.x86_64 18/18 Verifying : p11-kit-0.18.5-2.el6_5.2.x86_64 1/18 Verifying : nss-softokn-3.14.3-23.3.el6_8.x86_64 2/18 Verifying : nspr-4.11.0-1.el6.x86_64 3/18 Verifying : nss-3.21.3-2.el6_8.x86_64 4/18 Verifying : nss-tools-3.21.3-2.el6_8.x86_64 5/18 Verifying : nss-softokn-freebl-3.14.3-23.3.el6_8.x86_64 6/18 Verifying : nss-sysinit-3.21.3-2.el6_8.x86_64 7/18 Verifying : ca-certificates-2015.2.6-65.0.1.el6_7.noarch 8/18 Verifying : p11-kit-trust-0.18.5-2.el6_5.2.x86_64 9/18 Verifying : nss-util-3.21.3-1.el6_8.x86_64 10/18 Verifying : nspr-4.9-1.el6.x86_64 11/18 Verifying : nss-3.13.3-6.el6.x86_64 12/18 Verifying : nss-sysinit-3.13.3-6.el6.x86_64 13/18 Verifying : nss-tools-3.13.3-6.el6.x86_64 14/18 Verifying : ca-certificates-2010.63-3.el6_1.5.noarch 15/18 Verifying : nss-util-3.13.3-2.el6.x86_64 16/18 Verifying : nss-softokn-3.12.9-11.el6.x86_64 17/18 Verifying : nss-softokn-freebl-3.12.9-11.el6.x86_64 18/18 Dependency Installed: p11-kit.x86_64 0:0.18.5-2.el6_5.2 p11-kit-trust.x86_64 0:0.18.5-2.el6_5.2 Updated: ca-certificates.noarch 0:2015.2.6-65.0.1.el6_7 nss.x86_64 0:3.21.3-2.el6_8 Dependency Updated: nspr.x86_64 0:4.11.0-1.el6 nss-softokn.x86_64 0:3.14.3-23.3.el6_8 nss-softokn-freebl.x86_64 0:3.14.3-23.3.el6_8 nss-sysinit.x86_64 0:3.21.3-2.el6_8 nss-tools.x86_64 0:3.21.3-2.el6_8 nss-util.x86_64 0:3.21.3-1.el6_8 Complete! [root@mha1 ~]#
然后，重新启用YUM源：
[root@mha1 ~]# cat /etc/yum.repos.d/epel.repo [epel] name=Extra Packages for Enterprise Linux 6 - $basearch baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch failovermethod=priority enabled=1 gpgcheck=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 [epel-debuginfo] name=Extra Packages for Enterprise Linux 6 - $basearch - Debug baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch/debug #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-6&arch=$basearch failovermethod=priority enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 gpgcheck=0 [epel-source] name=Extra Packages for Enterprise Linux 6 - $basearch - Source baseurl=http://download.fedoraproject.org/pub/epel/6/SRPMS #mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-source-6&arch=$basearch failovermethod=priority enabled=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 gpgcheck=0 [root@mha1 ~]#
再次尝试之前失败的安装：
[root@mha1 ~]# yum install -y glib2-devel libpcap-devel libnet-devel Loaded plugins: fastestmirror, refresh-packagekit, security Loading mirror speeds from cached hostfile * base: mirrors.btte.net * extras: mirrors.163.com * remi-safe: mirrors.tuna.tsinghua.edu.cn * updates: mirrors.aliyun.com epel | 4.3 kB 00:00 epel/primary_db | 5.9 MB 00:17 Setting up Install Process Package glib2-devel-2.28.8-5.el6.x86_64 already installed and latest version Package 14:libpcap-devel-1.4.0-4.20130826git2dbcaa1.el6.x86_64 already installed and latest version Resolving Dependencies --> Running transaction check ---> Package libnet-devel.x86_64 0:1.1.6-7.el6 will be installed --> Processing Dependency: libnet(x86-64) = 1.1.6-7.el6 for package: libnet-devel-1.1.6-7.el6.x86_64 --> Processing Dependency: libnet.so.1()(64bit) for package: libnet-devel-1.1.6-7.el6.x86_64 --> Running transaction check ---> Package libnet.x86_64 0:1.1.6-7.el6 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================================================================================== Package Arch Version Repository Size ================================================================================================================================================== Installing: libnet-devel x86_64 1.1.6-7.el6 epel 181 k Installing for dependencies: libnet x86_64 1.1.6-7.el6 epel 58 k Transaction Summary ================================================================================================================================================== Install 2 Package(s) Total download size: 239 k Installed size: 1.4 M Downloading Packages: (1/2): libnet-1.1.6-7.el6.x86_64.rpm | 58 kB 00:00 (2/2): libnet-devel-1.1.6-7.el6.x86_64.rpm | 181 kB 00:00 -------------------------------------------------------------------------------------------------------------------------------------------------- Total 110 kB/s | 239 kB 00:02 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Installing : libnet-1.1.6-7.el6.x86_64 1/2 Installing : libnet-devel-1.1.6-7.el6.x86_64 2/2 Verifying : libnet-1.1.6-7.el6.x86_64 1/2 Verifying : libnet-devel-1.1.6-7.el6.x86_64 2/2 Installed: libnet-devel.x86_64 0:1.1.6-7.el6 Dependency Installed: libnet.x86_64 0:1.1.6-7.el6 Complete! [root@mha1 ~]#
可以看到，已经没问题了。
————————————
Done。