EX200 Practice Test 14 — 15 Questions

Question 1

Refer to the exhibit. The /proc/mdstat output shows a RAID1 array with two devices. One of the disks (/dev/sda1) fails. Which sequence of commands would be used to remove the failed disk and add a new replacement disk /dev/sdc1?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

mdadm /dev/md0 --fail /dev/sda1; mdadm /dev/md0 --remove /dev/sda1; mdadm /dev/md0 --add /dev/sdc1. It uses the proper mdadm syntax with the device name immediately after the command, followed by the action and the disk. The --fail flag marks the disk as faulty, --remove removes it from the array, and --add adds the new replacement disk. This sequence ensures the array remains in a degraded state before safely replacing the failed component.

Answer

mdadm --fail /dev/md0 /dev/sda1; mdadm --remove /dev/md0 /dev/sda1; mdadm --add /dev/md0 /dev/sdc1

Answer

mdadm /dev/md0 --set-faulty /dev/sda1; mdadm /dev/md0 --remove /dev/sda1; mdadm /dev/md0 --add /dev/sdc1

Answer

mdadm /dev/md0 --remove /dev/sda1; mdadm /dev/md0 --add /dev/sdc1

Answer

mdadm /dev/md0 --replace /dev/sda1 --with /dev/sdc1

Question 2

A server has a software RAID 5 array /dev/md0. One of its disks fails. The administrator wants to replace it without rebooting. Which command should be used to mark the disk as failed?

Accepted Answer

mdadm --fail /dev/md0 /dev/sdb. The correct command to mark a disk as failed in a software RAID array without rebooting is `mdadm --fail /dev/md0 /dev/sdb`. This command tells the md driver to mark the specified disk as faulty, which triggers the RAID 5 array to degrade and allows the failed disk to be removed and replaced while the system remains online.

Answer

mdadm --fault /dev/md0 /dev/sdb

Answer

echo faulty > /sys/block/md0/md/dev-sdb/state

Answer

mdadm --set-faulty /dev/md0 /dev/sdb

Question 3

An administrator needs to add a 1GB swap partition on /dev/sdd1. Which series of commands accomplishes this?

Accepted Answer

fdisk /dev/sdd, create partition, then mkswap /dev/sdd1, swapon /dev/sdd1, and add to /etc/fstab.. It includes all necessary steps: first create the partition with fdisk (since /dev/sdd1 does not exist yet), then format it as swap with mkswap, activate it with swapon, and finally add an entry to /etc/fstab to ensure persistence across reboots. The other options omit the critical partition creation step or fail to make the swap permanent.

Answer

mkswap /dev/sdd1 && echo '/dev/sdd1 swap swap defaults 0 0' >> /etc/fstab

Answer

mkfs.swap /dev/sdd1 && swapon /dev/sdd1

Answer

mkswap /dev/sdd1 && swapon /dev/sdd1

Question 4

A server has an LVM volume group vg01 with a physical volume /dev/sdb. The administrator wants to move all physical extents from /dev/sdb to /dev/sdd which is also in the same volume group. Which command sequence is correct?

Accepted Answer

pvmove /dev/sdb; vgreduce vg01 /dev/sdb. The correct sequence is to first use `pvmove /dev/sdb` to relocate all physical extents from /dev/sdb to other physical volumes in the same volume group (vg01), and then use `vgreduce vg01 /dev/sdb` to remove the now-empty physical volume from the volume group. This ensures no data loss and that the volume group metadata is properly updated.

Answer

vgreduce vg01 /dev/sdb; pvmove

Answer

pvmove /dev/sdb; pvremove /dev/sdb

Answer

pvmove /dev/sdb /dev/sdd

Question 5

A critical service must restart automatically after a crash. Which systemd directive should be added to the [Service] section of the service unit file?

Accepted Answer

Restart=always. The `Restart=always` directive in the `[Service]` section of a systemd unit file instructs systemd to automatically restart the service whenever it exits, regardless of the exit status. This ensures the critical service recovers immediately after a crash without manual intervention, which is essential for high-availability requirements.

Answer

OnFailure=

Answer

Requires=

Answer

Wants=

Question 6

A system fails to boot and drops into an emergency shell. The administrator suspects a misconfigured /etc/fstab. Which command should be used to determine which filesystem is causing the boot issue?

Accepted Answer

journalctl -xb -p err. When a system fails to boot due to a misconfigured /etc/fstab, the emergency shell is entered. The `journalctl -xb -p err` command displays the systemd journal from the current boot (`-b`) with extended information (`-x`) and filters for error-level messages (`-p err`). This will show the exact mount failure and the offending filesystem entry, making it the correct diagnostic tool.

Answer

systemctl status local-fs.target

Answer

fsck -A

Answer

mount -a

Question 7

A system administrator needs to create an XFS filesystem on /dev/sdb1 with the label 'data'. Which command should be used?

Accepted Answer

mkfs.xfs -L data /dev/sdb1. The `mkfs.xfs` command creates an XFS filesystem, and the `-L` flag assigns a label to the filesystem during creation. The command `mkfs.xfs -L data /dev/sdb1` correctly creates an XFS filesystem on the specified partition with the label 'data'.

Answer

mkfs.ext4 -L data /dev/sdb1

Answer

mkfs.xfs -l data /dev/sdb1

Answer

xfs_admin -L data /dev/sdb1

Question 8

A complex script uses 'trap' to handle signals. The admin writes 'trap '' SIGINT' to ignore Ctrl+C, but later in the script they want to re-enable the default behavior. Which command restores the default behavior for SIGINT?

Accepted Answer

trap - SIGINT. `trap - SIGINT` resets the signal handler for SIGINT to its default behavior. The `trap '' SIGINT` command sets an empty action, which ignores the signal; using `trap - signal` removes that custom handler and restores the default action (typically terminating the process).

Answer

trap : SIGINT

Answer

trap 2

Answer

trap SIGINT

Question 9

Refer to the exhibit. When the system boots, which filesystem will be mounted after the root filesystem?

Accepted Answer

/boot. According to the default boot process in RHEL 8/9, the initramfs mounts the root filesystem first, then the systemd-based init process mounts the /boot filesystem (if it is a separate partition) as specified in the /etc/fstab file. The root filesystem is mounted by the kernel or initramfs, and subsequent filesystems like /boot are mounted by systemd based on fstab entries.

Answer

None

Answer

Swap

Answer

Both /boot and swap

Question 10

After creating a new partition on /dev/sdc, the administrator runs 'partprobe' to inform the kernel of the change. What is the primary purpose of partprobe?

Accepted Answer

To make the kernel re-read the partition table. The `partprobe` command is used to inform the operating system kernel of changes to the partition table without requiring a system reboot. After creating a new partition on `/dev/sdc`, running `partprobe` makes the kernel re-read the partition table from the disk, ensuring the new partition is recognized and accessible. This is essential for the kernel to update its in-memory representation of the disk's partitions.

Answer

To create a filesystem label

Answer

To repair a damaged partition table

Answer

To format the partition with a filesystem

Question 11

An administrator writes a script to check disk usage and send an alert if usage exceeds 80%. The script uses 'df -h /' and parses the output. To maintain portability and avoid common pitfalls, which approach is recommended?

Accepted Answer

Use 'df / | awk 'NR==2 {print $5}' | tr -d '%'. It uses `df /` (without `-h`) to produce a stable, machine-parseable output where the fifth field (`$5`) is always the percentage used, and `awk` reliably extracts it. The `tr -d '%'` removes the percent sign for numeric comparison. This approach avoids the portability issues of parsing human-readable output from `df -h`, which can vary in column spacing and ordering across different Unix/Linux systems.

Answer

Use 'df -h / | tail -1 | sed 's/.* //' | tr -d '%'

Answer

Use 'df -h / | tail -1 | cut -d' ' -f5'

Answer

Use 'df -h / | grep -oP '\d+%'

Question 12

Refer to the exhibit. After mounting /dev/sdb1 with the noexec option, a script located at /mnt/data/test.file cannot be executed. What change will allow execution while maintaining security?

Accepted Answer

Change the mount option to exec in /etc/fstab and remount. The noexec mount option prevents execution of any binaries or scripts on the filesystem, regardless of file permissions. To allow execution while maintaining security, you must change the mount option to exec in /etc/fstab and remount the filesystem (e.g., mount -o remount,exec /mnt/data). This approach preserves other mount options and avoids the security risks of removing noexec globally.

Answer

Copy the script to /tmp and run from there

Answer

Use chmod +x /mnt/data/test.file

Answer

Remount without noexec and add setuid bit

Question 13

A helpdesk ticket states that user 'bob' cannot write to his own home directory. The directory /home/bob has permissions drwxr-xr-x and is owned by root:root. What command will fix this?

Accepted Answer

chown bob:bob /home/bob. The home directory /home/bob is owned by root:root with permissions drwxr-xr-x, meaning only root can write to it. User 'bob' cannot write because he is not the owner. Option D (chown bob:bob /home/bob) changes the owner and group to bob, granting him write access via the owner 'w' permission.

Answer

setfacl -m u:bob:rwx /home/bob

Answer

usermod -d /home/bob bob

Answer

chmod 755 /home/bob

Question 14

A system administrator writes a shell script to monitor disk usage and send an alert if any partition exceeds 80%. Which TWO of the following are best practices for implementing this script?

Accepted Answer

Include error handling to check for missing commands and exit gracefully.. Robust shell scripts should always include error handling to verify that required commands (e.g., `df`, `awk`, `grep`) are available before proceeding. This prevents the script from failing silently or producing misleading output, and allows it to exit gracefully with a meaningful error message, which is a key best practice for production scripts.

Answer

Use `cat /proc/partitions` to retrieve partition sizes.

Answer

Send alerts only via syslog (logger command).

Answer

Use `du -h /` and parse the output.

Question 15

An administrator needs to compress a directory containing subdirectories and files into a single archive file, with maximum compression, and exclude all '*.tmp' files. Which command should be used?

Accepted Answer

tar -cjvf archive.tar.bz2 --exclude='*.tmp' /path/to/dir. The question specifies 'maximum compression'. Among common tar compression methods, bzip2 (via the -j flag) typically provides better compression ratios than gzip (-z), though it is slower. Option C uses `tar -cjvf` with the `--exclude` option placed correctly before the source directory, which is the proper syntax for tar exclusions. This command creates a .tar.bz2 archive with maximum compression while excluding all *.tmp files. Option A uses gzip, which offers faster compression but lower ratios, making it incorrect for 'maximum compression'. Options B and D also fail: B has incorrect syntax (--exclude after the directory), and D omits the exclude option entirely.

Answer

tar -czvf archive.tar.gz --exclude='*.tmp' /path/to/dir

Answer

tar -czvf archive.tar.gz /path/to/dir --exclude='*.tmp'

Answer

tar -czvf archive.tar.gz /path/to/dir