第一步：
1]配置软件源
# vim /etc/yum.repos.d/upgrade.repo
[upgrade]
name=upgrade
baseurl=http://dev.centos.org/centos/6/upg/x86_64/
enable=1
gpgcheck=0
[2]安装软件工具
yum -y install preupgrade-assistant-contents redhat-upgrade-tool preupgrade-assistant
[3]升级前检查潜在问题
# preupg
Preupg tool doesn\'t do the actual upgrade.
Please ensure you have backed up your system and/or data in the event of a failed upgrade
that would require a full re-install of the system from installation media.Do you want to continue? y/n
y
Gathering logs used by preupgrade assistant:
All installed packages : 01/10 ...finished (time 00:00s)
All changed files : 02/10 ...finished (time 00:40s)
Changed config files : 03/10 ...finished (time 00:00s)
All users : 04/10 ...finished (time 00:00s)
All groups : 05/10 ...finished (time 00:00s)
Service statuses : 06/10 ...finished (time 00:00s)
All installed files : 07/10 ...finished (time 00:01s)
All local files : 08/10 ...finished (time 00:03s)
All executable files : 09/10 ...finished (time 00:00s)
RedHat signed packages : 10/10 ...finished (time 00:00s)
Assessment of the system, running checks / SCE scripts:
001/100 ...done (Configuration Files to Review)
002/100 ...done (File Lists for Manual Migration)
003/100 ...done (Bacula Backup Software)
004/100 ...done (MySQL configuration)
005/100 ...done (Migration of the MySQL data stack)
006/100 ...done (General changes in default MySQL implementation)
007/100 ...done (PostgreSQL upgrade content)
Assessment finished (time 00:00s)
Result table with checks and their results for main contents:
------------------------------------------------------------------------------------------
|System kickstart |notapplicable |
|YUM |notapplicable |
|Check for usage of dangerous range of UID/GIDs |notapplicable |
|Incorrect usage of reserved UID/GIDs |notapplicable |
|NIS ypbind config files back-up |notapplicable |
|NIS Makefile back-up |notapplicable |
|NIS server maps check |notapplicable |
|NIS server MAXUID and MAXGID limits check |notapplicable |
|NIS server config file back-up |notapplicable |
------------------------------------------------------------------------------------------
Tarball with results is stored here /root/preupgrade-results/preupg_results-140716022514.tar.gz .
The latest assessment is stored in directory /root/preupgrade .
Upload results to UI by command:
e.g. preupg -u http://127.0.0.1:8099/submit/ -r /root/preupgrade-results/preupg_results-*.tar.gz .
[4]开始升级
# rpm --import http://centos.excellmedia.net/7.0.1406/os/x86_64/RPM-GPG-KEY-CentOS-7
正常的运行以上命令可以升级完成；
# redhat-upgrade-tool --network 7.0 --instrepo http://centos.excellmedia.net/7.0.1406/os/x86_64/
这强制的就显得有点不友好了，生产环境慎用；
更新到这一步：
setting up repos...
.treeinfo | 1.1 kB 00:00
getting boot images...
vmlinuz-redhat-upgrade-tool | 4.7 MB 01:38
initramfs-redhat-upgrade-tool.img | 32 MB 14:45
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