RHEL6误使用了RHEL7的光盘源，安装了某个RPM包之后，导致glibc被升级，进而导致系统崩溃。
[root@rhel65 ~]# yum install ftp Loaded plugins: product-id, refresh-packagekit, security, subscription-manager This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register. Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package ftp.x86_64 0:0.17-67.el7 will be installed --> Processing Dependency: libc.so.6(GLIBC_2.15)(64bit) for package: ftp-0.17-67.el7.x86_64 --> Running transaction check ---> Package glibc.x86_64 0:2.12-1.132.el6 will be updated --> Processing Dependency: glibc = 2.12-1.132.el6 for package: glibc-headers-2.12-1.132.el6.x86_64 --> Processing Dependency: glibc = 2.12-1.132.el6 for package: glibc-common-2.12-1.132.el6.x86_64 --> Processing Dependency: glibc = 2.12-1.132.el6 for package: glibc-devel-2.12-1.132.el6.x86_64 ---> Package glibc.x86_64 0:2.17-157.el7 will be an update --> Running transaction check ---> Package glibc-common.x86_64 0:2.12-1.132.el6 will be updated ---> Package glibc-common.x86_64 0:2.17-157.el7 will be an update --> Processing Dependency: /usr/bin/bash for package: glibc-common-2.17-157.el7.x86_64 ---> Package glibc-devel.x86_64 0:2.12-1.132.el6 will be updated ---> Package glibc-devel.x86_64 0:2.17-157.el7 will be an update ---> Package glibc-headers.x86_64 0:2.12-1.132.el6 will be updated ---> Package glibc-headers.x86_64 0:2.17-157.el7 will be an update --> Running transaction check ---> Package bash.x86_64 0:4.1.2-15.el6_4 will be updated ---> Package bash.x86_64 0:4.2.46-20.el7_2 will be an update --> Processing Conflict: bash-4.2.46-20.el7_2.x86_64 conflicts filesystem < 3 --> Restarting Dependency Resolution with new changes. --> Running transaction check ---> Package filesystem.x86_64 0:2.4.30-3.el6 will be updated ---> Package filesystem.x86_64 0:3.2-21.el7 will be an update --> Finished Dependency Resolution Dependencies Resolved =========================================================================================================== Package Arch Version Repository Size =========================================================================================================== Installing: ftp x86_64 0.17-67.el7 rhel73-iso 61 k Updating: filesystem x86_64 3.2-21.el7 rhel73-iso 1.0 M Updating for dependencies: bash x86_64 4.2.46-20.el7_2 rhel73-iso 1.0 M glibc x86_64 2.17-157.el7 rhel73-iso 3.6 M glibc-common x86_64 2.17-157.el7 rhel73-iso 11 M glibc-devel x86_64 2.17-157.el7 rhel73-iso 1.1 M glibc-headers x86_64 2.17-157.el7 rhel73-iso 668 k Transaction Summary =========================================================================================================== Install 1 Package(s) Upgrade 6 Package(s) Total download size: 19 M Is this ok [y/N]: y Downloading Packages: ----------------------------------------------------------------------------------------------------------- Total 120 MB/s | 19 MB 00:00 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Updating : glibc-2.17-157.el7.x86_64 1/13 Updating : bash-4.2.46-20.el7_2.x86_64 2/13 Updating : glibc-common-2.17-157.el7.x86_64 3/13 Updating : glibc-headers-2.17-157.el7.x86_64 4/13 Updating : glibc-devel-2.17-157.el7.x86_64 5/13 Updating : filesystem-3.2-21.el7.x86_64 6/13 Error unpacking rpm package filesystem-3.2-21.el7.x86_64 error: unpacking of archive failed on file /bin: cpio: rename Installing : ftp-0.17-67.el7.x86_64 7/13 Cleanup : glibc-devel-2.12-1.132.el6.x86_64 8/13 Cleanup : glibc-headers-2.12-1.132.el6.x86_64 9/13 Cleanup : bash-4.1.2-15.el6_4.x86_64 10/13 Non-fatal POSTUN scriptlet failure in rpm package bash Cleanup : glibc-common-2.12-1.132.el6.x86_64 11/13 warning: %postun(bash-4.1.2-15.el6_4.x86_64) scriptlet failed, exit status 127 Cleanup : glibc-2.12-1.132.el6.x86_64 12/13 warning: /etc/localtime saved as /etc/localtime.rpmsave Non-fatal <unknown> scriptlet failure in rpm package glibc rhel65-iso/productid | 1.7 kB 00:00 ... rhel73-iso/productid | 1.6 kB 00:00 ... Verifying : glibc-devel-2.17-157.el7.x86_64 1/13 Verifying : bash-4.2.46-20.el7_2.x86_64 2/13 Verifying : glibc-2.17-157.el7.x86_64 3/13 Verifying : glibc-common-2.17-157.el7.x86_64 4/13 Verifying : ftp-0.17-67.el7.x86_64 5/13 Verifying : glibc-headers-2.17-157.el7.x86_64 6/13 Verifying : glibc-2.12-1.132.el6.x86_64 7/13 Verifying : glibc-devel-2.12-1.132.el6.x86_64 8/13 Verifying : bash-4.1.2-15.el6_4.x86_64 9/13 filesystem-2.4.30-3.el6.x86_64 was supposed to be removed but is not! Verifying : filesystem-2.4.30-3.el6.x86_64 10/13 Verifying : glibc-common-2.12-1.132.el6.x86_64 11/13 Verifying : glibc-headers-2.12-1.132.el6.x86_64 12/13 Verifying : filesystem-3.2-21.el7.x86_64 13/13 Installed: ftp.x86_64 0:0.17-67.el7 Dependency Updated: bash.x86_64 0:4.2.46-20.el7_2 glibc.x86_64 0:2.17-157.el7 glibc-common.x86_64 0:2.17-157.el7 glibc-devel.x86_64 0:2.17-157.el7 glibc-headers.x86_64 0:2.17-157.el7 Failed: filesystem.x86_64 0:2.4.30-3.el6 filesystem.x86_64 0:3.2-21.el7 Complete!
此时系统已经不能正常执行reboot命令重启了，只能强制按电源重启机器。重启之后，原系统已经崩溃，进不去系统了，停在下面的界面：
然后使用RHEL6的光盘引导机器，选择rescue，进入到shell之后提示无法chroot到/mnt/sysimage，无解。
然后重启，用RHEL6安装光盘引导机器，选择Install or Update系统，进入图形后选择update已有系统，失败，如下图。
然后按ctrl+alt+F2切换到第2个console，发现原系统已经被自动挂载到/mnt/sysimage目录，尝试chroot到/mnt/sysimage，由于bash被上面依赖更新了，所以会提示找不到/bin/sh，手动把/mnt/sysimage/usr/bin/sh 拷到 /mnt/sysimage/bin/sh，再次chroot成功。
手工挂载RHEL6的ISO到/mnt/rhel65并cd到Packages目录，强制将上面更新过的几个包更新回到RHEL6的版本：
# rpm --force --nodeps -Uvh [RPM包名]
分别把bash/glibc/glibc-common/glibc-devel/glibc-headers这几个包装回去。
重启系统，发现已经可以正常进入到原系统了，最后使用yum remove把最开始安装的RHEL7的包给remove掉，问题全部解决。