Scenario practice questions

Refer to the exhibit.

A user attempts to create a file in /backup/snapshots/ but receives an error. What is the most likely cause?

Exhibit

/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro)
/dev/sda2 on /var type ext4 (rw,relatime)
tmpfs on /run type tmpfs (rw,nosuid,nodev)
/dev/sdb1 on /backup type ext4 (ro)

Trap 1: The /backup directory does not exist.

The mount point exists; the error is likely not about missing directory.

Trap 2: The user does not have write permission on /backup.

Even with write permissions, the read-only mount prevents writes.

Trap 3: The /backup filesystem is full.

Not indicated; a full filesystem would give a 'no space left' error, but the mount flag is the primary issue.

A
The /backup filesystem is mounted read-only.
The '(ro)' flag indicates a read-only mount.
B
The /backup directory does not exist.
Why wrong: The mount point exists; the error is likely not about missing directory.
C
The user does not have write permission on /backup.
Why wrong: Even with write permissions, the read-only mount prevents writes.
D
The /backup filesystem is full.
Why wrong: Not indicated; a full filesystem would give a 'no space left' error, but the mount flag is the primary issue.

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Question 2mediummultiple choice

A server has two network interfaces: eth0 (10.0.0.10/24) and eth1 (192.168.1.10/24). The server needs to act as a router for a subnet 172.16.0.0/24, forwarding packets between it and the 10.0.0.0/24 network. Which sysctl parameter must be set to a value of 1 to enable IP forwarding?

Trap 1: net.core.forwarding

`net.core.forwarding` is not a valid sysctl parameter; the correct parameters are under the `net.ipv4` hierarchy.

Trap 2: net.ipv4.tcp_forwarding

`net.ipv4.tcp_forwarding` does not exist; TCP forwarding is not controlled by this parameter.

A
net.ipv4.conf.all.forwarding
This parameter enables IP forwarding globally for all network interfaces. It is a valid and effective method, so Option A is correct.
B
net.core.forwarding
Why wrong: `net.core.forwarding` is not a valid sysctl parameter; the correct parameters are under the `net.ipv4` hierarchy.
C
net.ipv4.tcp_forwarding
Why wrong: `net.ipv4.tcp_forwarding` does not exist; TCP forwarding is not controlled by this parameter.
D
net.ipv4.ip_forward
This is the classic kernel parameter for enabling IP forwarding globally. It is also correct; setting it to 1 enables forwarding.

Question 3mediummultiple choice

During boot, the system drops into a shell with message 'ERROR: No suitable file system found'. Filesystem corruption is suspected. Which sequence of actions should the admin take to attempt recovery?

Trap 1: Run xfs_repair -n /dev/sda.

Only applicable for XFS, and wrong partition.

Trap 2: Run e2fsck /dev/sda1 from the emergency shell.

Need to ensure filesystem is unmounted; e2fsck may not be appropriate for all fs types.

Trap 3: Mount the root filesystem manually, then run fsck.

Mounting a corrupted filesystem may cause further damage.

A
Run xfs_repair -n /dev/sda.
Why wrong: Only applicable for XFS, and wrong partition.
B
Determine the root device, then run 'fsck -y /dev/sda1'.
Fsck is filesystem-agnostic and with -y repairs automatically.
C
Run e2fsck /dev/sda1 from the emergency shell.
Why wrong: Need to ensure filesystem is unmounted; e2fsck may not be appropriate for all fs types.
D
Mount the root filesystem manually, then run fsck.
Why wrong: Mounting a corrupted filesystem may cause further damage.

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Question 4hardmultiple choice

A system administrator is configuring a custom systemd service that runs a Python script. The script logs output to stdout. The administrator wants to ensure that the service restarts automatically if it crashes, but only after a 10-second delay. Which directive should be added to the [Service] section of the unit file?

Trap 1: Restart=on-success RestartSec=10

Restarts on successful exit, not on failure.

Trap 2: Restart=always RestartSec=10

Restarts always, even on successful exit, which may not be desired.

Trap 3: RestartSec=10

Sets the delay but does not enable restarting on failure.

A
Restart=on-success RestartSec=10
Why wrong: Restarts on successful exit, not on failure.
B
Restart=on-failure RestartSec=10
Restarts the service only when it exits with a non-zero exit code or is terminated by a signal, with a 10-second delay.
C
Restart=always RestartSec=10
Why wrong: Restarts always, even on successful exit, which may not be desired.
D
RestartSec=10
Why wrong: Sets the delay but does not enable restarting on failure.

Question 5mediummultiple choice

A temporary contractor 'contractor1' has left the company. The administrator needs to remove the user account and all associated files in the home directory. Which command accomplishes this?

Trap 1: userdel contractor1

Deletes the user but leaves the home directory.

Trap 2: passwd -d contractor1

Deletes the password, not the account.

Trap 3: deluser --remove-home contractor1

deluser is Debian-specific; the question is distribution-agnostic for LFCS, so userdel is the standard command.

A
userdel contractor1
Why wrong: Deletes the user but leaves the home directory.
B
passwd -d contractor1
Why wrong: Deletes the password, not the account.
C
userdel -r contractor1
Removes the user and their home directory (-r).
D
deluser --remove-home contractor1
Why wrong: deluser is Debian-specific; the question is distribution-agnostic for LFCS, so userdel is the standard command.

Question 6mediummultiple choice

Scenario: You are managing a Linux server that hosts a web application. The application runs under the user 'webapp' and the group 'webgroup'. Recently, a new intern 'john' (username 'john') needs to be able to view and modify files in /var/www/html, which is owned by root:webgroup with permissions 775. John is currently a member of the group 'staff', but not 'webgroup'. The security policy requires that John must be able to edit files without using sudo, and his primary group must remain 'staff'. Which of the following actions should you take to meet the requirements?

Trap 1: Change the group ownership of /var/www/html to 'staff' and set the…

Incorrect: This would grant access to all staff members, which is too permissive.

Trap 2: Change John's primary group to 'webgroup' with 'usermod -g webgroup…

Incorrect: This changes his primary group, which may affect file creation in other directories.

Trap 3: Set the setgid bit on /var/www/html with 'chmod g+s /var/www/html'.

Incorrect: The setgid bit only affects new files; John still needs group membership to access existing files.

A
Add John to the 'webgroup' supplementary group with 'usermod -a -G webgroup john'.
Correct: John gains the group permissions of webgroup, allowing read/write access to the directory, while his primary group remains 'staff'.
B
Change the group ownership of /var/www/html to 'staff' and set the setgid bit.
Why wrong: Incorrect: This would grant access to all staff members, which is too permissive.
C
Change John's primary group to 'webgroup' with 'usermod -g webgroup john'.
Why wrong: Incorrect: This changes his primary group, which may affect file creation in other directories.
D
Set the setgid bit on /var/www/html with 'chmod g+s /var/www/html'.
Why wrong: Incorrect: The setgid bit only affects new files; John still needs group membership to access existing files.