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Chapter 4. Preparing the RHEL 7 system for an upgrade to RHEL 8
To prepare your RHEL 7 system for the upgrade to RHEL 8, follow these steps before proceeding with the upgrade:
Migrate the GRUB Legacy boot loader to GRUB2
After the upgrade, RHEL 7 still uses the GRUB Legacy boot loader. However, GRUB Legacy is not supported on RHEL 7 and later versions. Therefore, you must manually migrate the boot loader to GRUB2. For details, see the Upgrading from GRUB Legacy to GRUB 2 section in the
RHEL 7 System Administrator’s Guide
.- Resolve potential problems with installed packages. For details, see Section 7.1, “Ensuring that installed packages match the current major RHEL version”.
Adjust custom
System V
andUpstart
scripts tosystemd
services.On a RHEL 7 system,
systemd
replacesUpstart
as the init system. To use the featuressystemd
provides, such as parallel startup of system services at boot time, manually convert legacySystem V
andUpstart
scripts tosystemd
services. For details, see Converting traditional sysV init scripts to Red Hat Enterprise Linux 7 systemd unit files.Update paths to system directories in your scripts.
On a RHEL 7 system, the
/bin
,/sbin
,/lib
, and/lib64
directories have been replaced by symbolic links to their corresponding directory in/usr
. For example, on RHEL 8,/bin
is a symbolic link to the/usr/bin/
directory.If you use scripts or applications that expect
/bin
,/sbin
,/lib
, and/lib64
to be real directories, adjust them accordingly. For example, you can update the scripts and applications to:-
Use the paths in
/usr
, such as/usr/bin/
-
Accept that
/bin
,/sbin
,/lib
, and/lib64
are symbolic links instead of directories
-
Use the paths in
Update your YUM scripts and plug-ins to use the YUM 4 API.
RHEL 8 no longer supports the Python API of YUM 3. If you use any scripts or YUM plug-ins that use the legacy API, migrate them to the YUM 4 API. For more information, see Notable changes to the YUM stack.
-
If you miss certain packages after the upgrade, see the Section 7.3, “Installing missing packages after upgrading to RHEL 7” section in the
Troubleshooting
chapter. - Review the Considerations in adopting RHEL 8 document and make additional changes to your system if needed.
Update your system to the latest RHEL 7.9 version and reboot the host:
# yum update # reboot
- Ensure that all your applications and services are configured and work as expected. For example, if you run a DNS server on the host, verify that the configuration is still valid after the upgrade and that the service works in the same way as it did before the upgrade.
-
Follow the preparation steps described in the Preparing for the upgrade chapter in the
Upgrading from RHEL 7 to RHEL 8
document.