CompTIA CompTIA Certifications XK0-005 Questions & Answers

• Question 21:

  A Linux administrator is trying to remove the ACL from the file /home/user/data. txt but receives the following error message:

  

  Given the following analysis:

  

  Which of the following is causing the error message?

  A. The administrator is not using a highly privileged account.

  B. The filesystem is mounted with the wrong options.

  C. SELinux file context is denying the ACL changes.

  D. File attributes are preventing file modification.

  Correct Answer: D

  Explanation: File attributes are preventing file modification, which is causing the error message. The output of lsattr /home/user/data.txt shows that the file has the immutable attribute (i) set, which means that the file cannot be changed, deleted, or renamed. The command setfacl -b /home/user/data.txt tries to remove the ACL from the file, but fails because of the immutable attribute. The administrator needs to remove the immutable attribute first by using the command chattr -i /home/user/data.txt and then try to remove the ACL again. The other options are incorrect because they are not supported by the outputs. The administrator is using a highly privileged account, as shown by the # prompt. The filesystem is mounted with the correct options, as shown by the output of mount | grep /home. SELinux file context is not denying the ACL changes, as shown by the output of ls - Z /home/user/data.txt. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, pages 357-358.

• Question 22:

  A Linux administrator needs to create an image named sda.img from the sda disk and store it in the /tmp directory. Which of the following commands should be used to accomplish this task?

  A. dd of=/dev/sda if=/tmp/sda.img

  B. dd if=/dev/sda of=/tmp/sda.img

  C. dd --if=/dev/sda --of=/tmp/sda.img

  D. dd --of=/dev/sda --if=/tmp/sda.img

  Correct Answer: B

  Explanation: The command dd if=/dev/sda of=/tmp/sda.img should be used to create an image named sda.img from the sda disk and store it in the /tmp directory. The dd command is a tool for copying and converting data on Linux systems. The if option specifies the input file or device, in this case /dev/sda, which is the disk device. The of option specifies the output file or device, in this case /tmp/sda.img, which is the image file. The command dd if=/dev/sda of=/tmp/sda.img will copy the entire disk data from /dev/sda to /tmp/sda.img and create an image file. This is the correct command to use to accomplish the task. The other options are incorrect because they either use the wrong options (--if or --of instead of if or of) or swap the input and output (dd of=/dev/sda if=/tmp/sda.img or dd --of=/dev/sda --if=/tmp/sda.img). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Storage, page 323.

• Question 23:

  Which of the following is the best tool for dynamic tuning of kernel parameters?

  A. tuned

  B. tune2fs

  C. tuned-adm

  D. turbostat

  Correct Answer: A

  The tuned application is the best tool for dynamic tuning of kernel parameters, as it monitors the system and optimizes the performance under different workloads. It provides a number of predefined profiles for typical use cases, such as power saving, low latency, high throughput, virtual machine performance, and so on. It also allows users to create, modify, and delete profiles, and to switch between them on the fly. The tuned application uses the sysctl command and the configuration files in the /etc/sysctl.d/ directory to adjust the kernel parameters at runtime. References Chapter 2. Getting started with TuneD - Red Hat Customer Portal, paragraph 1 Kernel tuning with sysctl - Linux.com, paragraph 1

• Question 24:

  A Linux systems administrator is configuring a new filesystem that needs the capability to be mounted persistently across reboots. Which of the following commands will accomplish this task? (Choose two.)

  A. df -h /data

  B. mkfs.ext4 /dev/sdc1

  C. fsck /dev/sdc1

  D. fdisk -l /dev/sdc1

  E. echo "/data /dev/sdc1 ext4 defaults 0 0" >> /etc/fstab

  F. echo "/dev/sdc1 /data ext4 defaults 0 0" >> /etc/fstab

  Correct Answer: BF

  Explanation: "modify the /etc/fstab text file to automatically mount the new partition by opening it in an editor and adding the following line:

  /dev/ xxx 1 /data ext4 defaults 1 2

  where xxx is the device name of the storage device"

  https://learning.oreilly.com/library/view/mastering-linux-system/9781119794455/b01.xhtml To configure a new filesystem that needs the capability to be mounted persistently across reboots, two commands are needed: mkfs.ext4 /dev/sdc1

  and echo "/dev/sdc1 /data ext4 defaults 0 0" >> /etc/fstab. The first command creates an ext4 filesystem on the device /dev/sdc1, which is the partition that will be used for the new filesystem. The second command appends a line to the /etc/

  fstab file, which is the configuration file that controls persistent mount points of filesystems. The line specifies the device name, the mount point (/data), the filesystem type (ext4), the mount options (defaults), and the dump and pass values (0

  0). The other commands are incorrect because they either do not create or configure a filesystem, or they have wrong syntax or arguments. References: CompTIA Linux+ Study Guide, Fourth Edition, page 409-410, 414-415.

• Question 25:

  Users have been unable to save documents to /home/tmp/temp and have been receiving the following error:

  Path not found

  A junior technician checks the locations and sees that /home/tmp/tempa was accidentally created instead of /home/tmp/temp.

  Which of the following commands should the technician use to fix this issue?

  A. cp /home/tmp/tempa /home/tmp/temp

  B. mv /home/tmp/tempa /home/tmp/temp

  C. cd /temp/tmp/tempa

  D. ls /home/tmp/tempa

  Correct Answer: B

  Explanation: The mv /home/tmp/tempa /home/tmp/temp command will fix the issue of the misnamed directory. This command will rename the directory /home/tmp/tempa to /home/tmp/temp, which is the expected path for users to save their

  documents. The cp /home/tmp/tempa /home/tmp/temp command will not fix the issue, as it will copy the contents of /home/tmp/tempa to a new file named /home/tmp/temp, not a directory. The cd /temp/tmp/tempa command will not fix the

  issue, as it will change the current working directory to /temp/tmp/tempa, which does not exist. The ls /home/tmp/tempa command will not fix the issue, as it will list the contents of /home/tmp/tempa, not rename it. References: CompTIA Linux+

  (XK0-005) Certification Study Guide, Chapter 12:

  Managing Files and Directories, page 413.

• Question 26:

  A Linux engineer set up two local DNS servers (10.10.10.10 and 10.10.10.20) and was testing email connectivity to the local mail server using the mail command on a local machine when the following error appeared:

  

  The local machine DNS settings are:

  

  Which of the following commands could the engineer use to query the DNS server to get mail server information?

  A. dig @example.com 10.10.10.20 a

  B. dig @10.10.10.20 example.com mx

  C. dig @example.com 10.10.10.20 ptr

  D. dig @10.10.10.20 example.com ns

  Correct Answer: B

  Explanation: The command dig @10.10.10.20 example.com mx will query the DNS server to get mail server information. The dig command is a tool for querying DNS servers and displaying the results. The @ option specifies the DNS server to query, in this case 10.10.10.20. The mx option specifies the type of record to query, in this case mail exchange (MX) records, which identify the mail servers for a domain. The domain name to query is example.com. This command will show the MX records for example.com from the DNS server 10.10.10.20. This is the correct command to use to accomplish the task. The other options are incorrect because they either use the wrong syntax (@example.com 10.10.10.20 instead of @10.10.10.20 example.com), the wrong type of record (a or ptr instead of mx), or the wrong domain name (example.com ns instead of example.com mx). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter

  13: Managing Network Services, page 415.

• Question 27:

  A developer needs to launch an Nginx image container, name it Web001, and ex-pose port 8080 externally while mapping to port 80 inside the container. Which of the following commands will accomplish this task?

  A. docker exec --it -p 8080: 80 ----name Web001 nginx

  B. docker load -it -p 8080:80 ----name Web001 nginx

  C. docker run -it -P 8080:80 ----name Web001 nginx

  D. docker pull -it -p 8080:80 --name Web00l nginx

  Correct Answer: C

  To launch an Nginx image container, name it Web001, and expose port 8080 externally while mapping to port 80 inside the container, the administrator can use the command docker run -it -p 8080:80 --name Web001 nginx ? This will create

  and start a new container from the Nginx image, assign it a name of Web001, and map port 8080 on the host to port 80 on the container. The other commands are not valid or do not meet the requirements. References:

  [CompTIA Linux+ Study Guide], Chapter 11: Working with Containers, Section:

  Running Containers with Docker

  [How to Run Docker Containers]

• Question 28:

  A systems administrator created a new directory with specific permissions. Given the following output:

  # file: comptia

  # owner: root

  # group: root

  user: : rwx

  group :: r-x

  other: :--

  default:user :: rwx

  default:group :: r-x

  default:group:wheel: rwx

  default:mask :: rwx

  default:other ::

  Which of the following permissions are enforced on /comptia?

  A. Members of the wheel group can read files in /comptia.

  B. Newly created files in /comptia will have the sticky bit set.

  C. Other users can create files in /comptia.

  D. Only root can create files in /comptia.

  Correct Answer: A

  The output shows the file access control list (FACL) of the /comptia directory, which is an extension of the standard Linux permissions that allows more fine-grained control over file and directory access1. The FACL consists of two parts: the access ACL and the default ACL. The access ACL applies to the current object, while the default ACL applies to the objects created within the directory2. The access ACL has three entries: user, group, and other. These are similar to the standard Linux permissions, but they can be specified for individual users or groups as well. The user entry shows that the owner of the directory (root) has read, write, and execute permissions (rwx). The group entry shows that the group owner of the directory (root) has read and execute permissions (r-x). The other entry shows that all other users have no permissions (--). The default ACL has five entries: user, group, group:wheel, mask, and other. These are applied to any files or directories created within /comptia. The user entry shows that the owner of the new object will have read, write, and execute permissions (rwx). The group entry shows that the group owner of the new object will have read and execute permissions (r-x). The group:wheel entry shows that the members of the wheel group will have read, write, and execute permissions (rwx) on the new object. The mask entry shows that the maximum permissions allowed for any user or group are read, write, and execute (rwx). The other entry shows that all other users will have no permissions (--) on the new object. Therefore, based on the FACL output, members of the wheel group can read files in /comptia, as they have read permission on both the directory and any files within it. Option B is incorrect because the sticky bit is not set on /comptia or any files within it. The sticky bit is a special permission that prevents users from deleting or renaming files that they do not own in a shared directory3. It is symbolized by a t character in the execute position of others. Option C is incorrect because other users cannot create files in /comptia, as they have no permissions on the directory or any files within it. Option D is incorrect because root is not the only user who can create files in /comptia. Any user who has write permission on the directory can create files within it, such as members of the wheel group.

• Question 29:

  A Linux system is getting an error indicating the root filesystem is full. Which of the following commands should be used by the systems administrator to resolve this issue? (Choose three.)

  A. df -h /

  B. fdisk -1 /dev/sdb

  C. growpart /dev/mapper/rootvg-rootlv

  D. pvcreate /dev/sdb

  E. lvresize -L +10G -r /dev/mapper/rootvg-rootlv

  F. lsblk /dev/sda

  G. parted -l /dev/mapper/rootvg-rootlv

  H. vgextend /dev/rootvg /dev/sdb

  Correct Answer: ACE

  The administrator should use the following three commands to resolve the issue of the root filesystem being full:

  df -h /. This command will show the disk usage of the root filesystem in a human- readable format. The df command is a tool for reporting file system disk space usage. The -h option displays the sizes in powers of 1024 (e.g., 1K, 234M, 2G).

  The / specifies the root filesystem. The command df -h / will show the total size, used space, available space, and percentage of the root filesystem. This command will help the administrator identify the problem and plan the solution.

  growpart /dev/mapper/rootvg-rootlv. This command will grow the partition that contains the root filesystem to the maximum size available. The growpart command is a tool for resizing partitions on Linux systems. The /dev/mapper/rootvg-rootlv

  is the device name of the partition, which is a logical volume managed by the Logical Volume Manager (LVM). The command growpart /dev/mapper/rootvg-rootlv will extend the partition to fill the disk space and increase the size of the root

  filesystem. This command will help the administrator solve the problem and free up space.

  lvresize -L +10G -r /dev/mapper/rootvg-rootlv. This command will resize the logical volume that contains the root filesystem and add 10 GB of space. The lvresize command is a tool for resizing logical volumes on Linux systems. The -L option

  specifies the new size of the logical volume, in this case +10G, which means 10 GB more than the current size. The -r option resizes the underlying file system as well. The /dev/mapper/rootvg-rootlv is the device name of the logical volume,

  which is the same as the partition name. The command lvresize -L +10G -r /dev/mapper/rootvg-rootlv will increase the size of the logical volume and the root filesystem by 10 GB and free up space. This command will help the administrator

  solve the problem and free up space. The other options are incorrect because they either do not affect the root filesystem (fdisk - 1 /dev/sdb, pvcreate /dev/sdb, lsblk /dev/sda, or vgextend /dev/rootvg /dev/sdb) or do not use the correct syntax

  (fdisk -1 /dev/sdb instead of fdisk -l /dev/sdb or parted -l /dev/mapper/rootvg-rootlv instead of parted /dev/mapper/rootvg-rootlv print). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10:

  Managing Storage, pages 318-319, 331-332.

• Question 30:

  A Linux system fails to start and delivers the following error message:

  

  Which of the following commands can be used to address this issue?

  A. fsck.ext4 /dev/sda1

  B. partprobe /dev/sda1

  C. fdisk /dev/sda1

  D. mkfs.ext4 /dev/sda1

  Correct Answer: A

  Explanation: The command fsck.ext4 /dev/sda1 can be used to address the issue. The issue is caused by a corrupted filesystem on the /dev/sda1 partition. The error message shows that the filesystem type is ext4 and the superblock is invalid. The command fsck.ext4 is a tool for checking and repairing ext4 filesystems. The command will scan the partition for errors and attempt to fix them. This command can resolve the issue and allow the system to start. The other options are incorrect because they either do not fix the filesystem (partprobe or fdisk) or destroy the data on the partition (mkfs.ext4). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter

  10: Managing Storage, page 325.