RH134 - ch05s04

In this exercise, you adjust the scheduling priority of processes with the nice and renice commands, and observe the effects on process execution.

Outcomes

Adjust scheduling priorities for processes.

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

This command ensures that all required resources are available.

[student@workstation ~]$ lab start tuning-procscheduling

Important

This exercise uses commands that perform an endless checksum on a device file and intentionally use significant CPU resources.

Instructions

Use the ssh command to log in to the servera machine as the student user.

[student@workstation ~]$ ssh student@servera
...output omitted...
[student@servera ~]$

Determine the number of CPU cores on the servera machine, and then start two instances of the sha1sum /dev/zero & command for each core.
1. Use the grep command to parse the number of existing virtual processors (CPU cores) from the /proc/cpuinfo file.
```
[student@servera ~]$ grep -c '^processor' /proc/cpuinfo
2
```
2. Use a looping command to start multiple instances of the sha1sum /dev/zero & command. Start two instances for each virtual processor that was indicated in the previous step. In this example, a for loop creates four instances. The PID values in your output might vary from the example.
```
[student@servera ~]$ for i in {1..4}; do sha1sum /dev/zero & done
[1] 1132
[2] 1133
[3] 1134
[4] 1135
```

Verify that the background jobs are running for each of the sha1sum processes.

[student@servera ~]$ jobs
[1]   Running                 sha1sum /dev/zero &
[2]   Running                 sha1sum /dev/zero &
[3]-  Running                 sha1sum /dev/zero &
[4]+  Running                 sha1sum /dev/zero &

Use the ps and pgrep commands to display the percentage of CPU usage for each sha1sum process.

[student@servera ~]$ ps u $(pgrep sha1sum)
USER      PID %CPU %MEM    VSZ   RSS TTY     STAT START   TIME COMMAND
student  1132 49.6  0.1 225336  2288 pts/0   R    11:40   2:40 sha1sum /dev/zero
student  1133 49.6  0.1 225336  2296 pts/0   R    11:40   2:40 sha1sum /dev/zero
student  1134 49.6  0.1 225336  2264 pts/0   R    11:40   2:40 sha1sum /dev/zero
student  1135 49.6  0.1 225336  2280 pts/0   R    11:40   2:40 sha1sum /dev/zero

Terminate all sha1sum processes, and then verify that no jobs are running.

Use the pkill command to terminate all running processes with the sha1sum name pattern.

[student@servera ~]$ pkill sha1sum
[2]   Terminated              sha1sum /dev/zero
[4]+  Terminated              sha1sum /dev/zero
[1]-  Terminated              sha1sum /dev/zero
[3]+  Terminated              sha1sum /dev/zero

Verify that no jobs are running.

[student@servera ~]$ jobs
[student@servera ~]$

Start multiple instances of the sha1sum /dev/zero & command, and then start one additional instance of the sha1sum /dev/zero & command with a nice level of 10. Start at least as many instances as the number of system virtual processors. In this example, three regular instances are started, plus another with a higher nice level.
1. Use looping to start three instances of the sha1sum /dev/zero & command.
```
[student@servera ~]$ for i in {1..3}; do sha1sum /dev/zero & done
[1] 1207
[2] 1208
[3] 1209
```
2. Use the nice command to start the fourth instance with a nice level of 10.
```
[student@servera ~]$ nice -n 10 sha1sum /dev/zero &
[4] 1210
```
Use the ps and pgrep commands to display the PID, percentage of CPU usage, nice value, and executable name for each process. The instance with the nice value of 10 displays a lower percentage of CPU usage than the other instances.
```
[student@servera ~]$ ps -o pid,pcpu,nice,comm $(pgrep sha1sum)
  PID %CPU  NI COMMAND
 1207 64.2   0 sha1sum
 1208 65.0   0 sha1sum
 1209 63.9   0 sha1sum
 1210  8.2  10 sha1sum
```
Use the sudo renice command to lower the nice level of a process from the previous step. Use the PID value of the process instance with the nice level of 10 to lower its nice level to 5.
```
[student@servera ~]$ sudo renice -n 5 1210
[sudo] password for student: student
1210 (process ID) old priority 10, new priority 5
```

Repeat the ps and pgrep commands to display the CPU percentage and nice level.

[student@servera ~]$ ps -o pid,pcpu,nice,comm $(pgrep sha1sum)
  PID %CPU  NI COMMAND
 1207 62.9   0 sha1sum
 1208 63.2   0 sha1sum
 1209 63.2   0 sha1sum
 1210 10.9   5 sha1sum

Use the pkill command to terminate all running processes with the sha1sum name pattern.
```
[student@servera ~]$ pkill sha1sum
...output omitted...
```
Return to the workstation machine as the student user.
```
[student@servera ~]$ exit
logout
Connection to servera closed.
[student@workstation ~]$
```
Important
Verify that you have terminated all exercise processes before leaving this exercise.

Finish

On the workstation machine, change to the student user home directory and use the lab command to complete this exercise. This step is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish tuning-procscheduling

This concludes the section.

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Is It possible to reset root password when the system is on multi-user.target?

jennifer1987

27 lip 2023

Hi thereWell, i have a question, Is It possible to reset root password when the system is on multi-user.target? I was not be able to found a foro o some information related with this and another question that I have, If the grub menu dont show up, is it posible to reset the root password?

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Red Hat System Administration II (RH134)

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21 lip 2023

Build the skills to perform the key tasks needed to become a full-time Linux administratorRed Hat System Administration II (RH134) is the second part of the RHCSA training track for IT professionals who have already attended Red Hat System Administration I. The course goes deeper into core Linux system administration skills in storage configuration and management, installation and deployment of Red Hat Enterprise Linux, management of security features such as SELinux, control of recurring system tasks, management of the boot process and troubleshooting, basic system tuning, and command-line automation and productivity. This course assumes that students have attended Red Hat System Administration I (RH124).Experienced Linux administrators who seek rapid preparation for the RHCSA certification should instead start with RHCSA Rapid Track (RH199).This course is based on Red Hat Enterprise Linux 9.0.Course summaryInstall Red Hat Enterprise Linux using scalable methodsAccess security files, file systems, and networksExecute shell scripting and automation techniquesManage storage devices, logical volumes, and file systemsManage security and system accessControl the boot process and system servicesRun containersAudience for this courseThis course is geared toward Windows system administrators, network administrators, and other system administrators who are interested in supplementing current skills or backstopping other team members, in addition to Linux system administrators who are responsible for these tasks:Configuring, installing, upgrading, and maintaining Linux systems using established standards and proceduresProviding operational supportManaging systems for monitoring system performance and availabilityWriting and deploying scripts for task automation and system administrationRecommended trainingSuccessful completion of Red Hat System Administration I (RH124) is recommended.Experienced Linux administrators seeking to accelerate their path toward becoming a Red Hat Certified System Administrator should start with the RHCSA Rapid Track course (RH199).Take our free assessment to gauge whether this offering is the best fit for your skills.Technology considerationsThere are no special technology requirements.This course is not designed for bring your own device (BYOD).Internet access is not required, but is recommended to allow students to research and access Red Hat online resources.

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We are excited to launch a space dedicated to the Red Hat Training course Red Hat System Administration II! To gain the most value from this group - click the "Join Group" button in the upper right hand corner.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 RH134.Read more about Red Hat System Administration II here.

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