在青云上创建centos 6.4后，习惯性的安装emacs. 结果遇到报错信息：
# yum install emacs Loaded plugins: fastestmirror Determining fastest mirrors Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again
# yum upgrade ca-certificates --disablerepo=epel Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: mirrors.skyshe.cn * extras: ftp.sjtu.edu.cn * rpmfusion-free-updates: ftp.sjtu.edu.cn * rpmfusion-nonfree-updates: ftp.sjtu.edu.cn * updates: mirrors.skyshe.cn base | 3.7 kB 00:00 base/primary_db | 4.6 MB 00:04 emacs | 2.9 kB 00:02 emacs/primary_db | 37 kB 00:01 extras | 3.4 kB 00:00 extras/primary_db | 37 kB 00:00 rpmfusion-free-updates | 2.7 kB 00:00 rpmfusion-free-updates/primary_db | 272 kB 00:00 rpmfusion-nonfree-updates | 2.2 kB 00:00 rpmfusion-nonfree-updates/primary_db | 65 kB 00:00 updates | 3.4 kB 00:00 updates/primary_db | 5.2 MB 00:05 Setting up Upgrade 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 --> Processing Dependency: libtasn1.so.3(LIBTASN1_0_3)(64bit) for package: p11-kit-0.18.5-2.el6_5.2.x86_64 --> Processing Dependency: libtasn1.so.3()(64bit) for package: p11-kit-0.18.5-2.el6_5.2.x86_64 ---> Package p11-kit-trust.x86_64 0:0.18.5-2.el6_5.2 will be installed --> Running transaction check ---> Package libtasn1.x86_64 0:2.3-6.el6_5 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 0:3.14.0.0-12.el6 will be updated --> Processing Dependency: nss = 3.14.0.0-12.el6 for package: nss-tools-3.14.0.0-12.el6.x86_64 --> Processing Dependency: nss = 3.14.0.0-12.el6 for package: nss-sysinit-3.14.0.0-12.el6.x86_64 ---> Package nss.x86_64 0:3.21.0-0.3.el6_7 will be an update --> Processing Dependency: nss-util >= 3.21.0 for package: nss-3.21.0-0.3.el6_7.x86_64 --> Processing Dependency: nss-softokn(x86-64) >= 3.14.3-22 for package: nss-3.21.0-0.3.el6_7.x86_64 --> Processing Dependency: nspr >= 4.11.0 for package: nss-3.21.0-0.3.el6_7.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.21)(64bit) for package: nss-3.21.0-0.3.el6_7.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.17.1)(64bit) for package: nss-3.21.0-0.3.el6_7.x86_64 --> Processing Dependency: libnssutil3.so(NSSUTIL_3.15)(64bit) for package: nss-3.21.0-0.3.el6_7.x86_64 --> Running transaction check ---> Package nspr.x86_64 0:4.9.2-1.el6 will be updated ---> Package nspr.x86_64 0:4.11.0-0.1.el6_7 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.el6_7 will be an update --> Processing Dependency: nss-softokn-freebl(x86-64) >= 3.14.3-23.el6_7 for package: nss-softokn-3.14.3-23.el6_7.x86_64 ---> Package nss-sysinit.x86_64 0:3.14.0.0-12.el6 will be updated ---> Package nss-sysinit.x86_64 0:3.21.0-0.3.el6_7 will be an update ---> Package nss-tools.x86_64 0:3.14.0.0-12.el6 will be updated ---> Package nss-tools.x86_64 0:3.21.0-0.3.el6_7 will be an update ---> Package nss-util.x86_64 0:3.14.0.0-2.el6 will be updated ---> Package nss-util.x86_64 0:3.21.0-0.3.el6_7 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.el6_7 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 updates 1.2 M nss x86_64 3.21.0-0.3.el6_7 updates 858 k Installing for dependencies: libtasn1 x86_64 2.3-6.el6_5 base 238 k 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 4.11.0-0.1.el6_7 updates 114 k nss-softokn x86_64 3.14.3-23.el6_7 updates 262 k nss-softokn-freebl x86_64 3.14.3-23.el6_7 updates 167 k nss-sysinit x86_64 3.21.0-0.3.el6_7 updates 46 k nss-tools x86_64 3.21.0-0.3.el6_7 updates 435 k nss-util x86_64 3.21.0-0.3.el6_7 updates 67 k Transaction Summary ============================================================================================================================================================================================== Install 3 Package(s) Upgrade 8 Package(s) Total download size: 3.5 M Is this ok [y/N]: y Downloading Packages: (1/11): ca-certificates-2015.2.6-65.0.1.el6_7.noarch.rpm | 1.2 MB 00:01 (2/11): libtasn1-2.3-6.el6_5.x86_64.rpm | 238 kB 00:00 (3/11): nspr-4.11.0-0.1.el6_7.x86_64.rpm | 114 kB 00:00 (4/11): nss-3.21.0-0.3.el6_7.x86_64.rpm | 858 kB 00:00 (5/11): nss-softokn-3.14.3-23.el6_7.x86_64.rpm | 262 kB 00:00 (6/11): nss-softokn-freebl-3.14.3-23.el6_7.x86_64.rpm | 167 kB 00:00 (7/11): nss-sysinit-3.21.0-0.3.el6_7.x86_64.rpm | 46 kB 00:00 (8/11): nss-tools-3.21.0-0.3.el6_7.x86_64.rpm | 435 kB 00:00 (9/11): nss-util-3.21.0-0.3.el6_7.x86_64.rpm | 67 kB 00:00 (10/11): p11-kit-0.18.5-2.el6_5.2.x86_64.rpm | 94 kB 00:00 (11/11): p11-kit-trust-0.18.5-2.el6_5.2.x86_64.rpm | 71 kB 00:00 ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Total 601 kB/s | 3.5 MB 00:06 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Updating : nspr-4.11.0-0.1.el6_7.x86_64 1/19 Updating : nss-util-3.21.0-0.3.el6_7.x86_64 2/19 Updating : nss-softokn-freebl-3.14.3-23.el6_7.x86_64 3/19 Updating : nss-softokn-3.14.3-23.el6_7.x86_64 4/19 Updating : nss-sysinit-3.21.0-0.3.el6_7.x86_64 5/19 Updating : nss-3.21.0-0.3.el6_7.x86_64 6/19 Installing : libtasn1-2.3-6.el6_5.x86_64 7/19 Installing : p11-kit-0.18.5-2.el6_5.2.x86_64 8/19 Installing : p11-kit-trust-0.18.5-2.el6_5.2.x86_64 9/19 Updating : ca-certificates-2015.2.6-65.0.1.el6_7.noarch 10/19 Updating : nss-tools-3.21.0-0.3.el6_7.x86_64 11/19 Cleanup : ca-certificates-2010.63-3.el6_1.5.noarch 12/19 Cleanup : nss-tools-3.14.0.0-12.el6.x86_64 13/19 Cleanup : nss-3.14.0.0-12.el6.x86_64 14/19 Cleanup : nss-sysinit-3.14.0.0-12.el6.x86_64 15/19 Cleanup : nss-softokn-3.12.9-11.el6.x86_64 16/19 Cleanup : nss-util-3.14.0.0-2.el6.x86_64 17/19 Cleanup : nspr-4.9.2-1.el6.x86_64 18/19 Cleanup : nss-softokn-freebl-3.12.9-11.el6.x86_64 19/19 Verifying : p11-kit-0.18.5-2.el6_5.2.x86_64 1/19 Verifying : nss-util-3.21.0-0.3.el6_7.x86_64 2/19 Verifying : nss-softokn-3.14.3-23.el6_7.x86_64 3/19 Verifying : nss-softokn-freebl-3.14.3-23.el6_7.x86_64 4/19 Verifying : nss-sysinit-3.21.0-0.3.el6_7.x86_64 5/19 Verifying : libtasn1-2.3-6.el6_5.x86_64 6/19 Verifying : nss-3.21.0-0.3.el6_7.x86_64 7/19 Verifying : ca-certificates-2015.2.6-65.0.1.el6_7.noarch 8/19 Verifying : nspr-4.11.0-0.1.el6_7.x86_64 9/19 Verifying : nss-tools-3.21.0-0.3.el6_7.x86_64 10/19 Verifying : p11-kit-trust-0.18.5-2.el6_5.2.x86_64 11/19 Verifying : nss-tools-3.14.0.0-12.el6.x86_64 12/19 Verifying : nss-3.14.0.0-12.el6.x86_64 13/19 Verifying : ca-certificates-2010.63-3.el6_1.5.noarch 14/19 Verifying : nss-softokn-freebl-3.12.9-11.el6.x86_64 15/19 Verifying : nss-util-3.14.0.0-2.el6.x86_64 16/19 Verifying : nss-sysinit-3.14.0.0-12.el6.x86_64 17/19 Verifying : nspr-4.9.2-1.el6.x86_64 18/19 Verifying : nss-softokn-3.12.9-11.el6.x86_64 19/19 Dependency Installed: libtasn1.x86_64 0:2.3-6.el6_5 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 0:3.21.0-0.3.el6_7 Dependency Updated: nspr.x86_64 0:4.11.0-0.1.el6_7 nss-softokn.x86_64 0:3.14.3-23.el6_7 nss-softokn-freebl.x86_64 0:3.14.3-23.el6_7 nss-sysinit.x86_64 0:3.21.0-0.3.el6_7 nss-tools.x86_64 0:3.21.0-0.3.el6_7 nss-util.x86_64 0:3.21.0-0.3.el6_7 Complete!
现在可以了。