RH342 - ch06s02

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Guided Exercise: Resolving Package Dependency Issues

Resolve a package dependency issue, and then lock the prerequisite package to the relevant version.

Outcomes

You should be able to resolve package dependency issues.

As the student user on the workstation machine, use the lab command to prepare your system for this exercise.

[student@workstation ~]$ lab start rpm-dependency

Instructions

The security team recently updated the system requirements for hosts in the data center. The update requires installing a custom package, rht-main, on each host.

A colleague attempted unsuccessfully to install rht-main on servera. You are asked to resolve this issue and to verify that the rht-main package installs successfully. After installing the rht-main package, ensure that you can update the prerequisite rht-prereq package. Create a version lock for the rht-prereq-0.1-1.el8 package.

[student@workstation ~]$ ssh student@servera
...output omitted...
[student@servera ~]$ sudo -i
[sudo] password for student: student
[root@servera ~]#

Reproduce the issue, to collect and record troubleshooting information.

Use YUM to install the rht-main package. View the transaction messages.

[root@servera ~]# yum install rht-main
Last metadata expiration check: 2:29:27 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
Error:
 Problem: package rht-main-0.1-1.el8.noarch requires rht-prereq = 0.1-1.el8, but none of the providers can be installed
  - conflicting requests
  - package rht-prereq-0.1-1.el8.noarch is filtered out by exclude filtering
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

The transaction message indicates that the rht-main package requires a specific version (0.1-1.el8) of the rht-prereq package.

Use the yum install -v command to generate verbose transaction details.

[root@servera ~]# yum -v install rht-main
Loaded plugins: builddep, changelog, config-manager, copr, debug, debuginfo-install, download, generate_completion_cache, groups-manager, kpatch, needs-restarting, playground, repoclosure, repodiff, repograph, repomanage, reposync, uploadprofile, versionlock
YUM version: 4.4.2
...output omitted...
Last metadata expiration check: 3:11:29 ago on Mon 18 Oct 2021 07:59:41 PM EDT.
Completion plugin: Generating completion cache...
Versionlock plugin: number of lock rules from file "/etc/dnf/plugins/versionlock.list" applied: 1
--> Starting dependency resolution
--> Finished dependency resolution
Error:
 Problem: package rht-main-0.1-1.el8.noarch requires rht-prereq = 0.1-1.el8, but none of the providers can be installed
  - conflicting requests
  - package rht-prereq-0.1-1.el8.noarch is filtered out by exclude filtering
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

The Versionlock plugin line indicates that a single package is present in the version lock list. Therefore, your next steps are to view dependencies and to verify whether a version lock is the root cause of the issue.

Use the yum deplist command to view the rht-main package dependencies.

[root@servera ~]# yum deplist rht-main
Last metadata expiration check: 2:01:55 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
package: rht-main-0.1-1.el8.noarch
  dependency: rht-prereq = 0.1-1.el8
   provider: rht-prereq-0.1-1.el8.noarch

To list all versions, both installed and available, of the rht-prereq package that are known to the YUM configuration, use the yum list --showduplicates command.
```
[root@servera ~]# yum list --showduplicates rht-prereq
Last metadata expiration check: 2:01:24 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
Installed Packages
rht-prereq.noarch                0.2-1.el8                             @rht_lab
Available Packages
rht-prereq.noarch                0.1-1.el8                             rht_lab
rht-prereq.noarch                0.2-1.el8                             rht_lab
```
The command output indicates that a later version of the rht-prereq package, 0.2-1.el8, is already installed. However, the rht-main package requires an earlier version of the rht-prereq package. Because YUM automatically resolves package requirements even with version conflicts, additional troubleshooting is required.
To determine whether any packages have specific version locks, use the yum versionlock command.
```
[root@servera ~]# yum versionlock
Last metadata expiration check: 2:02:30 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
rht-prereq-0:0.2-1.el8.*
```
The rht-prereq package is locked to a later version than the required version.

To resolve the version lock conflict, delete the version lock for the rht-prereq-0:0.2-1.el8 package.

[root@servera ~]# yum versionlock delete rht-prereq-0:0.2-1.el8
Last metadata expiration check: 2:59:52 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
Deleting versionlock for: rht-prereq-0:0.2-1.el8.*

Confirm the deletion.

[root@servera ~]# yum versionlock
Last metadata expiration check: 3:00:06 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
[root@servera ~]#

Use the yum command to install the mandated rht-main package.

[root@servera ~]# yum install rht-main
Last metadata expiration check: 3:05:12 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
Dependencies resolved.
===============================================================================
 Package            Architecture        Version        Repository         Size
===============================================================================
Installing:
 rht-main           noarch              0.1-1.el8      rht_lab            6.8 k
Downgrading:
 rht-prereq         noarch              0.1-1.el8      rht_lab            6.7 k

Transaction Summary
===============================================================================
Install    1 Package
Downgrade  1 Package

Total size: 13 k
Is this ok [y/N]: y
Downloading Packages:
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                        1/1
  Downgrading      : rht-prereq-0.1-1.el8.noarch                            1/3
  Installing       : rht-main-0.1-1.el8.noarch                              2/3
  Cleanup          : rht-prereq-0.2-1.el8.noarch                            3/3
  Verifying        : rht-prereq-0.1-1.el8.noarch                            1/3
  Verifying        : rht-prereq-0.2-1.el8.noarch                            2/3
  Verifying        : rht-main-0.1-1.el8.noarch                              3/3

Downgraded:
  rht-prereq-0.1-1.el8.noarch
Installed:
  rht-main-0.1-1.el8.noarch

Complete!

As displayed in the transaction summary, the yum command downgrades the rht-prereq package from version 0.2-1 to 0.1-1; installs the rht-main package; and then removes the rht-prereq-0.2-1.el8.noarch package.

Now that the rht-main package is installed, attempt to update the prerequisite rht-prereq package. Because of dependencies, YUM generates an error message and fails.

[root@servera ~]# yum update rht-prereq
Last metadata expiration check: 3:58:51 ago on Wed 13 Oct 2021 05:41:46 PM EDT.
Error:
 Problem: problem with installed package rht-main-0.1-1.el8.noarch
  - package rht-main-0.1-1.el8.noarch requires rht-prereq = 0.1-1.el8, but none of the providers can be installed
  - cannot install both rht-prereq-0.2-1.el8.noarch and rht-prereq-0.1-1.el8.noarch
  - cannot install the best update candidate for package rht-prereq-0.1-1.el8.noarch
(try to add '--allowerasing' to command line to replace conflicting packages or '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

Create a version lock for the installed rht-prereq package. Adding a version lock ensures that YUM ignores any attempt to update the rht-prereq-0.1-1.el8 package.
1. To lock the installed version of the rht-prereq package, use the yum versionlock add command.
```
[root@servera ~]# yum versionlock add rht-prereq
Last metadata expiration check: 0:32:06 ago on Wed 13 Oct 2021 09:52:41 PM EDT.
Adding versionlock on: rht-prereq-0:0.1-1.el8.*
```
2. Verify that the versionlock list includes the rht-prereq-0:0.1-1.el8 package.
```
[root@servera ~]# yum versionlock
Last metadata expiration check: 0:34:09 ago on Wed 13 Oct 2021 09:52:41 PM EDT.
rht-prereq-0:0.1-1.el8.*
```

To verify that YUM no longer prints an error message when attempting to update the rht-prereq package, run the yum update command again.

[root@servera ~]# yum update rht-prereq
Last metadata expiration check: 0:36:01 ago on Wed 13 Oct 2021 09:52:41 PM EDT.
Dependencies resolved.
Nothing to do.
Complete!

Return to workstation as the student user.

[root@servera ~]# exit
[student@servera ~]$ exit
[student@workstation ~]$

Finish

On the workstation machine, use the lab command to complete this exercise. This is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish rpm-dependency

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Welcome to the Red Hat Enterprise Linux Diagnostics and Troubleshooting (RH342) group!

cschunke

26 wrz 2023

We are excited to launch a space dedicated to the Red Hat Training course Red Hat Enterprise Linux Diagnostics and Troubleshooting! To gain the most value from this group - click the "Join Group" button in the upper right hand corner of the group home page.We encourage group members to collaborate in this group to discuss topics, ask questions, share best practices and tips, provide course feedback, and share their accomplishments as it relates to RH342.Read more about Red Hat Enterprise Linux Diagnostics and Troubleshooting here.

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Revision: rh342-8.4-6dd89bd

Click Create to build all of the virtual machines needed for the classroom lab environment. This may take several minutes to complete. Once created the environment can then be stopped and restarted to pause your experience.
When a lab is created, click Start to run all of the virtual machines in the classroom.
Click Stop to stop all the virtual machines from running. This will not delete your lab.
If you Delete your lab, you will remove all of the virtual machines in your classroom and lose all of your progress.

Virtual machine actions

Click Start to power on the virtual machine.
Click Shutdown to gracefully shut down the virtual machine, preserving disk contents.
Click Power off to forcefully shut down the virtual machine, while still preserving disk contents.
Click Open console to connect to the system console of the virtual machine in a new browser.

Auto-stop timer

The Red Hat Learning Subscription entitles you to set allotment of lab time.
To help conserving your allotted time, the lab environment uses automatic timers to stop or destroy your lab environment when the timer expires.

Click the Auto-stop button [+] to extend the time you would like to spend with the labs.
Click the Auto-destroy button [+] to add day(s) to the auto-destroy timer.

Auto-stop has a maximum of 11 hours, and auto-destroy has a maximum of 14 days.
Be careful to keep the timers set while you are working, so that your environment doesn't shut down unexpectedly.
We also suggest not to set the auto-timers unnecessarily high, which could waste your lab time allotment