RH134 - ch03s04

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

Outcomes

You should be able to adjust scheduling priorities for processes.

From workstation, run the lab tuning-procscheduling start command. The command runs a start script to determine if the servera host is reachable on the network.

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

From workstation use SSH to log in to servera as the student user. The systems are configured to use SSH keys for authentication, so a password is not required.
```
[student@workstation ~]$ ssh student@servera
...output omitted...
[student@servera ~]$ 
```
Determine the number of CPU cores on servera and then start two instances of the sha1sum /dev/zero & command for each core.
1. Use grep 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 per virtual processor found in the previous step. In this example, that would be four instances. The PID values in your output will vary from the example.
```
[student@servera ~]$ for i in $(seq 1 4); do sha1sum /dev/zero & done
[1] 2643
[2] 2644
[3] 2645
[4] 2646
```

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   2643 49.8  0.0 228360  1744 pts/0    R    11:15   6:09 sha1sum /dev/zero
student   2644 49.8  0.0 228360  1780 pts/0    R    11:15   6:09 sha1sum /dev/zero
student   2645 49.8  0.0 228360  1748 pts/0    R    11:15   6:09 sha1sum /dev/zero
student   2646 49.8  0.0 228360  1780 pts/0    R    11:15   6:09 sha1sum /dev/zero

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

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

[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 there are no running jobs.

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

Start multiple instances of sha1sum /dev/zero &, then start one additional instance of sha1sum /dev/zero & with a nice level of 10. Start at least as many instances as the system has virtual processors. In this example, 3 regular instances are started, plus another with the higher nice level.
1. Use looping to start three instances of sha1sum /dev/zero &.
```
[student@servera ~]$ for i in $(seq 1 3); do sha1sum /dev/zero & done
[1] 1947
[2] 1948
[3] 1949
```
2. Use the nice command to start the fourth instance with a 10 nice level.
```
[student@servera ~]$ nice -n 10 sha1sum /dev/zero &
[4] 1953
```
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 should display a lower percentage of CPU usage than the other instances.
```
[student@servera ~]$ ps -o pid,pcpu,nice,comm $(pgrep sha1sum)
  PID %CPU  NI COMMAND
 1947 66.0   0 sha1sum
 1948 65.7   0 sha1sum
 1949 66.1   0 sha1sum
 1953  6.7  10 sha1sum
```
Use the sudo renice command to lower the nice level of a process from the previous step. Note the PID value from the process instance with the nice level of 10. Use that process PID to lower its nice level to 5.
```
[student@servera ~]$ sudo renice -n 5 1953
[sudo] password for student: student
1953 (process ID) old priority 10, new priority 5
```

Repeat the ps and pgrep commands to redisplay the CPU percent and nice level.

[student@servera ~]$ ps -o pid,pcpu,nice,comm $(pgrep sha1sum)
  PID %CPU  NI COMMAND
 1947 63.8   0 sha1sum
 1948 62.8   0 sha1sum
 1949 65.3   0 sha1sum
 1953  9.1   5 sha1sum

Use the pkill command to terminate all running processes with the name pattern sha1sum.
```
[student@servera ~]$ pkill sha1sum
...output omitted...
```

Exit from servera.

[student@servera ~]$ exit
logout
Connection to servera closed.
[student@workstation ~]$

Finish

On workstation, run the lab tuning-procscheduling finish script to finish this exercise.

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

This concludes the guided exercise.

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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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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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