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Linux+ (XK0-006). Set it up and run it.
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The five questions
1. An administrator edits GRUB_CMDLINE_LINUX in /etc/default/grub on a RHEL 9 server that boots in legacy BIOS mode. Which command writes that change into the boot loader configuration the machine will actually read at the next boot?
- A. grub2-mkconfig -o /boot/grub2/grub.cfg
- B. update-grub
- C. grub2-install --target=i386-pc /dev/sda
- D. dracut -f /boot/initramfs-6.8.0.img
Correct answer: A.
On RHEL and its derivatives the generator is grub2-mkconfig, and the output file must be named explicitly. On a BIOS system that file is /boot/grub2/grub.cfg. The command reads /etc/default/grub and the scripts in /etc/grub.d and rebuilds the menu from them.
Why the others are wrong. B: update-grub is a Debian and Ubuntu wrapper script; it is not shipped on RHEL, and the file it targets is /boot/grub/grub.cfg. C: That reinstalls the boot loader images into the MBR and /boot/grub2; it does not regenerate the menu from /etc/default/grub. D: dracut rebuilds the initramfs image for the running kernel and never touches the GRUB menu or its kernel command line.
2. /srv/team must become a shared area where the team group can create and edit files and every new file automatically takes the team group. Which two commands together achieve that? (Choose two.)
- A. chgrp team /srv/team
- B. chmod +t /srv/team
- C. chmod 2770 /srv/team
- D. setfacl -b /srv/team
- E. chattr +i /srv/team
Correct answer: A.
chgrp sets the directory's group to team, and 2770 sets the setgid bit (2) with rwx for owner and group and nothing for others. Together they give drwxrws--- owned by the team group, so new entries inherit team.
Why the others are wrong. B: The sticky bit restricts deletion and renaming; it has no influence on the group a new file receives. D: -b removes every extended ACL entry from the directory, which takes access away rather than granting it. E: The immutable attribute would stop anyone, including root, creating files in the directory at all.
3. On Ubuntu 22.04 the kernel parameter transparent_hugepage=never must be present at every boot, and must survive future kernel package updates. Which file should be edited before update-grub is run?
- A. /boot/grub/grub.cfg
- B. /proc/cmdline
- C. /etc/default/grub
- D. /etc/grub.d/40_custom
Correct answer: C.
GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub is the supported place for persistent kernel parameters. update-grub then rebuilds /boot/grub/grub.cfg, and every generated menu entry, including entries for kernels installed later, picks the parameter up.
Why the others are wrong. A: That file is generated by update-grub, so any hand edit is discarded the next time a kernel update triggers a regeneration. B: It is a read-only view of the parameters the running kernel was given; nothing written there survives, and it is not a configuration file. D: That script is the place to append extra menu entries of your own; it does not change the command line of the generated entries.
4. A deployment script is inspected before a change window: $ ls -l /opt/app/deploy.sh | -rwxr-x--- 1 build devops 2104 Mar 3 08:12 /opt/app/deploy.sh . Which numeric mode matches the permissions shown?
- A. 750
- B. 740
- C. 755
- D. 775
Correct answer: A.
Read the string in three groups: owner rwx is 4+2+1 = 7, group r-x is 4+0+1 = 5, others --- is 0. The mode is 750.
Why the others are wrong. B: 740 is -rwxr-----; the group field here shows r-x, and the execute bit adds 1 to make 5. C: 755 is -rwxr-xr-x, which would let every account on the host read and run the script; the others field is --- here. D: 775 is -rwxrwxr-x; that gives the devops group write access and others read and execute, neither of which the listing shows.
5. A script contains: #!/bin/bash | count=0 | for f in /var/log/app/*.log; do count=$((count+1)); done | echo "$count" . The directory holds four .log files and one .txt file. What does the script print, and what would it print if the directory held no .log files at all?
- A. 4 in the first case and 1 in the second, because an unmatched pattern is left as a literal word
- B. 4 in the first case and 0 in the second, because the loop body is skipped when nothing matches
- C. 5 in the first case and 0 in the second, because the .txt file is counted as well
- D. 4 in the first case and an error in the second, because the loop cannot iterate over a missing file
Correct answer: A.
The pattern expands to the four matching names, so the counter reaches 4. With nothing to match, bash leaves the word as the literal string /var/log/app/*.log, so the loop still runs exactly once and the script prints 1.
Why the others are wrong. B: That is the behaviour only after shopt -s nullglob; with the default setting the unmatched pattern survives as text and the body runs once, printing 1. C: The pattern *.log cannot match a name ending in .txt, so that file is never part of the expansion and the first count stays at 4. D: A for loop iterates over words rather than over files that must exist, so an unmatched pattern produces one ordinary iteration and no error.
6. A BIOS server stops during boot with: error: file '/boot/grub2/i386-pc/normal.mod' not found. | Entering rescue mode... | grub rescue> . At that prompt ls reports (hd0) (hd0,msdos1) (hd0,msdos2), and ls (hd0,msdos1)/ lists grub2 and vmlinuz-5.14.0-427.el9.x86_64. What is the correct sequence at the rescue prompt to reach a normal boot menu?
- A. set prefix=(hd0,msdos1)/grub2, set root=(hd0,msdos1), insmod normal, normal
- B. insmod normal, normal, then grub2-mkconfig -o /boot/grub2/grub.cfg
- C. set root=(hd0,msdos2), insmod linux, linux /vmlinuz, boot
- D. ls (hd0,msdos1)/, cat (hd0,msdos1)/grub2/grub.cfg, then boot
Correct answer: A.
The rescue shell has only a handful of built-in commands because it could not find its module directory. Pointing prefix at the directory that actually holds the modules lets insmod normal load the full GRUB, and normal then draws the menu. The listing shows the modules live on the first partition, so prefix must name that partition.
Why the others are wrong. B: insmod cannot find the module until prefix points at the directory holding it, so this fails with the same file not found error. C: That hand-boots a kernel with no initramfs and no root= argument, and msdos2 is not the partition the listing shows the modules on. D: Reading the configuration file proves it exists but never loads it; the rescue shell cannot act on grub.cfg without the normal module.
7. After a reboot an administrator must confirm that a kernel parameter added to the boot loader really reached the running kernel. Which command shows the parameters the running kernel was started with?
- A. cat /etc/default/grub
- B. cat /proc/cmdline
- C. uname -a
- D. sysctl -a
Correct answer: B.
The kernel exposes its own command line, exactly as the boot loader handed it over, in /proc/cmdline. It reflects the running kernel, so it settles whether the boot loader change took effect.
Why the others are wrong. A: That shows what the administrator intended the next generated menu to contain, not what the kernel actually received. C: uname reports the kernel release, build date and architecture; it prints nothing about boot parameters. D: sysctl lists runtime kernel tunables under /proc/sys, which are a different set of values from the boot command line.
8. A shared project directory is created on a RHEL 9 host with: $ sudo chmod 2770 /srv/projects/atlas . Which line will ls -ld /srv/projects/atlas now display?
- A. drwxrwx--T 2 root atlas 4096 Apr 2 10:15 /srv/projects/atlas
- B. drwsrwx--- 2 root atlas 4096 Apr 2 10:15 /srv/projects/atlas
- C. drwxrws--- 2 root atlas 4096 Apr 2 10:15 /srv/projects/atlas
- D. drwxrwxr-x 2 root atlas 4096 Apr 2 10:15 /srv/projects/atlas
Correct answer: C.
2 is the setgid bit, 7 is rwx for the owner, 7 is rwx for the group and 0 is nothing for others. Because the group already has execute permission, the setgid bit prints as a lowercase s in the group execute position: drwxrws---.
Why the others are wrong. A: A trailing T is the sticky bit with no execute for others, which is mode 1770, not 2770. B: An s in the owner execute position is the setuid bit, mode 4770; the leading 2 sets setgid, which lands in the group field. D: That is plain 0775 with no special bit at all, and it also gives others read and execute.
