Red Hat Enterprise Linux 6 升级 Red Hat Enterprise Linux 7
lonesomer 2016-10-17
前言
因为交易系统部的同事提出了一个新的需求要将现有的RHEL6.7升级至RHEL7.1(最好保留数据升级)，之前对于小版本的升级无论是CentOS还是RedHat都可以直接通过yum update的方式实现软件包和内核的迭代更新，但是这次的需求经过Redhat知识库的研究发现这几乎是一个不可能轻松实现的任务，原因就是Redhat压根不支持大版本之间的升级，考虑到跨版本兼容性问题和原厂不做技术支持这两点，通过和Redhat二线电话沟通也确认了最终的实现方案，就是先备份相关重要配置和数据格式化/分区保留其它文件系统，重装后在把数据迁移回来。整个过程虽然提不上什么惊心动魄，但至少翻阅了大量材料，官方虽然给出了跨版本升级的步骤，但实现的代价和要求真的太高，这里一并分享出来方便大家学习和思考。
How do I upgrade from RHEL 6 to RHEL 7? Reinstall
扩展阅读
红帽支持 RHEL 主版本之间的升级吗？- https://access.redhat.com/zh_...
How do I upgrade from RHEL 6 to RHEL 7? - https://access.redhat.com/sol...
红帽支持 RHEL 主版本之间的升级吗？
Environment
- Red Hat Enterprise Linux 4
- Red Hat Enterprise Linux 5
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
Issue
- 如何从红帽企业版 Linux 的一个版本升级到另一个版本？
- 可以从 RHEL 的不同主版本之间移植吗？
- 红帽支持 RHEL 主版本之间的升级吗（比如从5升级到6）？
- 可以在 RHEL 5 上安装 RHEL 6 吗？
- 安装介质没有包含升级选项；
- 如何从
RHEL 5升级到RHEL 6？
Resolution
Red Hat Enterprise Linux 4, 5, 6
红帽 不支持 RHEL 主版本之间的跨大版本升级。（主版本以整数表示。比如，RHEL 5 和 RHEL 6 都是不同的主版本。）
不同主版本之间的跨大版本升级，不会保留所有系统设置、服务配置和自定义设置。因此， 红帽强烈建议重新安装系统，以进行主版本之间的升级 。建议在运行着的服务器旁，使用新的服务器安装一个全新的RHEL，然后把原有的设 置、软件和数据迁移到新服务器上，以确保系统和软件能在新服务器上正确运行。 这还有助于确保数据安全地从备份转移到新的系统。
还有方法可以不进行全新安装，来进行升级。要实现这个功能，插入新版本的安装光盘，然后在 boot 命令行中输入：
# linux upgradeany
这将引导您进行与 普通的安装过程很相近的升级步骤。再次说明，这个过程红帽是不予支持的。进行完这个升级操作后，如果您联系红帽技术支持，红帽只会当作全新的安装来提供支持。升级过程中产生的问题是不予支持的。任何时候出现的问题如果疑似与升级过程有关，红帽将要求您重新安装系统。
Comment
- 红帽建议，系统升级之前要先全面备份数据。
- 如果之前安装有第三方软件，建议在新系统上重新安装。
- 更换新版本系统后，个别软件包的配置文件可能会失效，因为新版本配置文件的格式和排列可能会有所变化。
- 如果之前安装有红帽的 layered products （比如 Cluster Suite）, 需要在新系统完全安装之后，手动升级它们。
- 用升级选项进行升级，系统可能会出现不稳定的情况。
- 如果出现意外情况，红帽全球支持只能建议您按照建议的方式，重新安装系统并进行迁移。
可参考文档， Red Hat Enterprise Linux 6 Installation Guide, Chapter 37. Upgrading Your Current System
升级或重新安装系统后，请重新注册系统，请参考 Red Hat Enterprise Linux 6 Installation Guide, Chapter 37. Upgrading Your Current System
Red Hat Enterprise Linux 7
对于特定的使用情况，红帽支持从 Red Hat Enterprise Linux 6 升级到 Red Hat Enterprise Linux 7 。更多信息，请参考以下文档：
- How do I upgrade from RHEL 6 to RHEL 7?
- What are the supported use cases for upgrading from RHEL 6 to RHEL 7?
- How do I subscribe to the RHEL Extras channel/repo?
- Red Hat Enterprise Linux 7 Installation Guide
如有问题，请联系红帽全球支持服务 file a support case ，或在 Discussions area of the Customer Portal 中进行讨论。
How do I upgrade from RHEL 6 to RHEL 7
Environment
Red Hat Enterprise Linux 6.x to Red Hat Enterprise Linux 7
| Product Variant | x86 Architecture | x86_64 Architecture | IBM Power | IBM z Systems |
|---|---|---|---|---|
| Desktop Edition | Not supported | Not supported | N/A | N/A |
| Workstation Edition | Not supported | Not supported | N/A | N/A |
| Server Edition | Not supported | <font color=blue>Supported</font> | <font color=blue>Supported[1]</font> | <font color=blue>Supported[2]</font> |
| HPC Compute Node | Not supported | <font color=blue>Supported</font> | N/A | N/A |
| Server running CloudForms software | N/A | Not supported | N/A | N/A |
[1] Red Hat Enterprise Linux for Power, big endian
[2] Red Hat Enterprise Linux for IBM z Systems
Issue
How do I do in-place upgrading from the latest Red Hat Enterprise Linux 6 to the latest Red Hat Enterprise Linux 7?
How do I use the preupgrade assistant and redhat-upgrade-tool to run a RHEL6 to RHEL7 upgrade?
Resolution
Red Hat Enterprise Linux 7 (RHEL 7) is the first major release of RHEL to allow in-place upgrades from the previous RHEL major release (RHEL 6). An in-place upgrade offers a way of upgrading a system to a new major release of Red Hat Enterprise Linux by replacing the existing operating system.
This RHEL 6 to RHEL 7 upgrade procedure is fully supported if your Red Hat Enterprise Linux system meets the following criteria:
Latest Red Hat Enterprise Linux 6: Before upgrading to the latest RHEL 7, you must start with RHEL 6 and update your system to have the latest RHEL 6 packages installed. (This is covered in the procedure below.)
All Server editions (except x86): All server editions (except x86) of Red Hat Enterprise Linux 6 can be upgraded with this procedure. Upgrades of RHEL Workstation and Desktop systems are not supported. Upgrades for the POWER architecture is supported. SEE TABLE ABOVE. Upgrade from 32-bit architecture is not supported.
Limited package groups: The upgrade process handles only the following package groups and packages: Minimal (@minimal), Base (@base), Web Server (@web-server), DHCP Server, File Server (@nfs-server), and Print Server (@print-server). Although upgrades of other packages and groups are not supported, in some cases, packages can be uninstalled from the RHEL 6 system and reinstalled on the upgraded RHEL 7 system without a problem. SEE TABLE BELOW.
The supported use cases for upgrading RHEL 6 to RHEL 7:
| Supported | Unsupported | |
|---|---|---|
| Source to Upgrade | The latest RHEL-6.X | RHEL 6.4 and earlier |
| File Systems | Like-file system upgrades For example ext3 to ext3, ext4 to ext4, xfs to xfs | Unlike-file system upgrades For example ext4 to xfs |
| GNOME, KDE | None | All GNOME, KDE installs |
| Packages/Groups | Minimal (@minimal) Base (@base) Web Server (@web-server) DHCP Server File Server (@nfs-server) Print Server | All others |
| Virtualization | KVM, VMWare | Microsoft Hyper-V (coming soon) |
| Red Hat Software Collections | Using tested process | All others |
| High Availability | None | All |
The upgrade procedure consists of the following basic steps:
- Prepare for Upgrade: Make sure your system is backed up and up to date before beginning the preupgrade.
- Install the Preupgrade Assistant: Enable the required repositories and install the preupgrade packages.
- Run the Preupgrade Assistant: Check your system for upgrade issues before running the actual upgrade. No changes are made to your system and you can repeat this step until all issues are dealt with.
- Run the Upgrade: Perform the actual upgrade.
- Provide Feedback: Create a debug log to send to Red Hat in case there are problems.
实践步骤
核心目标为格式化/分区，保留其它文件系统，做好相应备份重装RHEL7
生产环境当前系统版本为RHEL6.7，推荐升级至RHEL7.1或者更新的版本
通过RHEL7.1的ISO引导至INSTALLATION SUMMARY
- DATE & TIME设置为Asia/Shanghai timezone
- LANGUAGE SUPPORT添加English(United States),简体中文(中国)
- SOFTWARE SELECTION设置为Server with GUI
- UBSTAKKATUIB DESTINATION分区选择I will configure partioning，点击DONE
- 找到现有系统中的/分区，选中后在右侧勾选Reformat，Mount Point设置为/，SYSTEM其它分区SWAP,/boot,/usr,/tmp,/var参照同样操作，DATA数据分区不动，点击DONE
- Begin Install
- 安装结束后恢复备份数据
- 恢复原有网卡配置项和IP地址
- 恢复主机名/Hosts/Profile
- 恢复fstab分区检查数据一致性
