A Linux systems administrator is troubleshooting an I/O latency on a single CPU server. The administrator runs a top command and receives the following output:
%Cpu(s): 0.2 us, 33.1 sy, 0.0 ni, 0.0 id, 52.4 wa, 0.0 hi, 0.2 si, 0.0 st
Which of the following is correct based on the output received from the exe-cuted command?
Correct Answer:
C
The server’s CPU is spending too much time waiting for data inputs. This can be inferred from the output of the top command, which shows the percentage of CPU time spent in different states. The wa state stands for wait, and it indicates that the CPU is idle while waiting for an I/O operation to complete. In this case, the wa state is 52.4%, which means that more than half of the CPU time is wasted on waiting for data inputs. This can cause a high I/O latency and affect the performance of the server.
The other options are not correct based on the output received from the executed command. The server’s CPU is not taking too long to process users’ requests, because the us state, which stands for user, is only 0.2%, which means that the CPU is barely used by user processes. The server’s CPU does not show a high idle-time value, because the id state, which stands for idle, is 0.0%, which means that the CPU is not idle at all. The server’s CPU value for the time spent on system processes is not low, because the sy state, which stands for system, is 33.1%, which means that the CPU is heavily used by system processes.
References: How to Use the Linux top Command (and Understand Its Output); [Understanding Linux CPU Load - when should you be worried?]
An administrator needs to make an application change via a script that must be run only in console mode. Which of the following best represents the sequence the administrator should execute to accomplish this task?
Correct Answer:
A
The correct answer is A. systemctl isolate multi-user.target sh script.sh systemctl isolate graphical.target
This sequence will allow the administrator to switch from the graphical mode to the console mode, run the script, and then switch back to the graphical mode.
The systemctl command is used to control the systemd system and service manager, which manages the boot targets and services on Linux systems. The isolate subcommand starts the unit specified on the command line and its dependencies and stops all others. The multi-user.target is a boot target that provides a text-based console login, while the graphical.target is a boot target that provides a graphical user interface. By using systemctl isolate, the administrator can change the boot target on the fly without rebooting the system.
The sh command is used to run a shell script, which is a file that contains a series of commands that can be executed by the shell. The script.sh is the name of the script that contains the application change that the administrator needs to make. By running sh script.sh, the administrator can execute the script in the console mode.
The other options are incorrect because:
* B. systemctl isolate graphical.target sh script.sh systemctl isolate multi-user.target
This sequence will switch from the console mode to the graphical mode, run the script, and then switch back to the console mode. This is not what the administrator wants to do, as the script must be run only in console mode.
* C. sh script.sh systemctl isolate multi-user.target systemctl isolate graphical.target
This sequence will run the script in the current mode, which may or may not be console mode, and then switch to console mode and back to graphical mode. This is not what the administrator wants to do, as the script must be run only in console mode.
* D. systemctl isolate multi-user.target systemctl isolate graphical.target sh script.sh
This sequence will switch from graphical mode to console mode and then back to graphical mode, without running the script at all. This is not what the administrator wants to do, as the script must be run only in console mode.
References:
✑ systemctl(1) - Linux manual page
✑ How to switch between the CLI and GUI on a Linux server
✑ How to PROPERLY boot into single user mode in RHEL/CentOS 7/8
✑ Changing Systemd Boot Target in Linux
✑ Exit Desktop to Terminal in Ubuntu 19.10
Which of the following commands is used to configure the default permissions for new files?
Correct Answer:
C
The command that is used to configure the default permissions for new files is umask. The umask command is a tool for setting the default permissions for new files and directories on Linux systems. The umask value is a four-digit octal number that represents the permissions that are subtracted from the default permissions. The default permissions for files are 666, which means read and write for owner, group, and others.
The default permissions for directories are 777, which means read, write, and execute for owner, group, and others. The umask value consists of four digits: the first digit is for special permissions, such as setuid, setgid, and sticky bit; the second digit is for the owner permissions; the third digit is for the group permissions; and the fourth digit is for the others permissions. The umask value can be calculated by subtracting the desired permissions from the default permissions. For example, if the desired permissions for files are 664, which means read and write for owner and group, and read for others, then the umask
value is 002, which is 666 - 664. The command umask 002 will set the umask value to 002, which will ensure that only file owners and group members can modify new files by default. The command that is used to configure the default permissions for new files is umask. This is the correct answer to the question. The other options are incorrect because they either do not set the default permissions for new files (setenforce, sudo, or chmod) or do not exist (kill -HUP or kill -TERM). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing File Permissions and Ownership, page 349.
An administrator needs to increase the system priority of a process with PID 2274. Which of the following commands should the administrator use to accomplish this task?
Correct Answer:
A
The renice command is used to change the priority of a running process by specifying its PID and the new nice value. The -n flag indicates the amount of change in the nice value, which can be positive or negative. A lower nice value means a higher priority, so -15 will increase the priority of the process with PID 2274. The administrator needs to have root privileges to do this.
References:
✑ The renice command is listed as one of the commands to manipulate process priority in the web search result 1.
✑ The renice command is also explained with examples in the web search result 2.
✑ The CompTIA Linux+ Certification Exam Objectives mention that the candidate should be able to “manage process execution priorities” as part of the System Operation and Maintenance domain1.
A developer wants to ensure that all files and folders created inside a shared folder named
/GroupOODEV inherit the group name of the parent folder. Which of the following commands will help achieve this goal?
Correct Answer:
D
The chmod command is used to change the permissions of files and directories on Linux systems. The g+s option sets the setgid bit on a directory, which means that all files and folders created inside that directory will inherit the group name of the parent directory. This command can help the developer ensure that all files and folders created inside the /GroupOODEV directory have the same group name as /GroupOODEV. References: [How to Use chmod Command in Linux with Examples]
