LFCS Essential Commands Practice Test 2 — 15 Questions

Question 1

An administrator needs to find the process ID of the cron daemon. Which combination of commands is most effective?

Accepted Answer

pidof cron. `pidof cron` directly returns the numeric process ID(s) of the cron daemon by searching the process name in the `/proc` filesystem. It is the most straightforward command for this specific task, as it outputs only the PID without additional formatting or filtering.

Answer

top -p $(pgrep cron)

Answer

pgrep cron

Answer

ps -C cron -o pid=

Question 2

An administrator wants to find all files larger than 100MB in the /home directory. Which two commands or command sequences achieve this? (Choose two.)

Accepted Answer

find /home -type f -size +100M. Option A is correct because GNU find's -size +100M uses the M suffix to mean 1,048,576-byte units (MiB), so +100M matches regular files strictly larger than 100 MiB in /home. Option D is correct because the k suffix means 1,024-byte units, so +102400k equals 102400 × 1024 = 104,857,600 bytes, the same threshold as 100 MiB, and -type f restricts results to regular files. Option B is wrong because +100000000c compares against 100,000,000 bytes (about 95.4 MiB), not 100 MiB. Option C is wrong because find does not accept the MB suffix; valid size suffixes are b, c, w, k, M, and G. Option E is wrong because the size 100M (without +) matches files of exactly 100 MiB, not files larger than 100MB.

Answer

find /home -type f -size +100000000c

Answer

find /home -type f -size +100MB

Answer

find /home -type f -size 100M

Question 3

Refer to the exhibit.

A user attempts to read /etc/passwd and receives "Permission denied". What is the most likely reason?

Accepted Answer

The user does not have execute permission on the /etc directory.. To read a file, a user needs both read permission on the file itself and execute permission on every directory in the path leading to it. The /etc directory typically has permissions 755 (drwxr-xr-x), which grants execute permission to the owner and group but not to others. If the user is not the owner and not in the group, they lack execute (x) on /etc, which prevents them from traversing into the directory to access /etc/passwd, even if the file's permissions would otherwise allow reading.

Answer

The user is not in the root group.

Answer

The file has the immutable attribute set.

Answer

The user does not have read permission on the file.

Question 4

Refer to the exhibit.

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

Accepted Answer

The /backup filesystem is mounted read-only.. The error occurs because the /backup filesystem is mounted read-only, which prevents any write operations, including file creation, regardless of directory permissions or available space. This is a common scenario when a filesystem is intentionally mounted with the 'ro' option in /etc/fstab or via the mount command to protect data integrity.

Answer

The /backup directory does not exist.

Answer

The user does not have write permission on /backup.

Answer

The /backup filesystem is full.

Question 5

Refer to the exhibit.

The /data directory needs to be resized to 15GB. What is the first step?

Accepted Answer

Unmount the filesystem.. The first step to resize a filesystem is to unmount it, because most filesystem resizing tools (such as resize2fs for ext4) require the filesystem to be unmounted to safely modify the underlying block device without risking data corruption. Attempting to resize a mounted filesystem can lead to inconsistent metadata and data loss. Unmounting ensures no processes are actively writing to the filesystem during the resize operation.

Answer

Resize the partition using fdisk.

Answer

Create a new partition and copy data.

Answer

Resize the filesystem using resize2fs.

Question 6

A system administrator needs to find all files in /var/log that have been modified in the last 7 days. Which command accomplishes this?

Accepted Answer

find /var/log -mtime -7. The `-mtime -7` option in the `find` command matches files whose content was modified less than 7 days ago (i.e., within the last 7 days). The minus sign before the number indicates 'less than' or 'within the last N days', which is exactly what the system administrator needs to find files modified in the last 7 days.

Answer

find /var/log -mtime +7

Answer

find /var/log -mtime 7

Answer

find /var/log -atime -7

Question 7

A user is unable to execute a script in their home directory. The script has permissions -rw-r--r--. Which command will allow the user to execute the script?

Accepted Answer

chmod u+x script.sh. The script's permissions -rw-r--r-- indicate the owner has read and write but not execute. Both `chmod u+x script.sh` (adds execute for owner) and `chmod 755 script.sh` (sets owner to rwx, group/others to r-x) grant the user execute permission, allowing them to run the script. Option B is the minimal change, but option D also works; thus both are correct. Options A and C are incorrect because they would either remove execute or only add it for 'others', not the user.

Answer

chmod a-x script.sh

Answer

chmod o+x script.sh

Question 8

A script needs to search for lines containing 'ERROR' in /var/log/syslog and count them. Which command pipeline achieves this?

Accepted Answer

grep ERROR /var/log/syslog | wc -l. It uses `grep` to filter lines containing 'ERROR' from `/var/log/syslog` and pipes the output to `wc -l`, which counts the number of lines. This pipeline accurately counts the lines that match the pattern, which is the required task.

Answer

wc -l /var/log/syslog

Answer

grep ERROR /var/log/syslog | wc -c

Answer

grep -c ERROR /var/log/syslog

Question 9

Based on the exhibit, what is the average CPU idle percentage over the last 15 minutes?

Accepted Answer

65.0%. The average CPU idle percentage over the last 15 minutes is calculated from the 'idle' value in the 'average' row of the 'mpstat' output. In the exhibit, the 'average' row shows an 'idle' value of 65.0, meaning the CPU was idle 65.0% of the time on average across all CPUs over the 15-minute interval. Therefore, the correct answer is 65.0%.

Answer

2.0

Answer

1.5

Answer

2.5

Question 10

The backup script fails to run as user 'backup' with sudo. What is the issue?

Accepted Answer

The script does not have execute permission for the 'backup' user.. For a script to be executed via sudo, the user (backup) must have execute permission on the script file. Even if sudo is configured to allow the user to run the script, the operating system enforces file permission checks at execution time. Without the execute bit set for the backup user (or for others, depending on the sudo runas context), the kernel will refuse to execve() the script, resulting in a 'Permission denied' error.

Answer

The script has a restrictive umask.

Answer

The script is not owned by 'backup'.

Answer

The 'backup' user is not in the sudoers file.

Question 11

Which TWO commands can be used to change the ownership of a file to a specific user and group? (Select two.)

Accepted Answer

chown alice:staff file.txt. Option A, `chown alice:staff file.txt`, is correct because chown changes both the owning user and the owning group in a single command, setting the owner to alice and the group to staff. Option C, `chgrp staff file.txt`, is correct because chgrp changes the group ownership of the file to staff, which is one of the ownership attributes being modified. Option B, `chmod 755 file.txt`, is incorrect because chmod changes permission bits (read/write/execute), not ownership. Option D, `usermod -G staff alice`, is incorrect because it modifies alice's supplementary group membership, not file ownership. Option E, `passwd alice`, is incorrect because it changes alice's password, not file ownership.

Answer

chmod 755 file.txt

Answer

usermod -G staff alice

Answer

passwd alice

Question 12

Which THREE commands can be used to view the contents of a compressed archive file without extracting it? (Select three.)

Accepted Answer

tar -tvf archive.tar.gz. Option A, `tar -tvf archive.tar.gz`, is correct because the `-t` flag lists the contents of the archive and `-v` provides a verbose listing, while `-f` specifies the archive file, all without extracting anything. Option B, `zcat archive.gz`, is correct because `zcat` decompresses the gzip file and writes the uncompressed data to standard output, letting you view the contents without creating an extracted file on disk. Option D, `less archive.gz`, is correct because `less` transparently decompresses gzip files and displays them in a pager, so you can read the contents without extracting. Option C, `gunzip archive.gz`, is not correct because it decompresses the file and replaces the .gz with the uncompressed file, which is extraction rather than viewing. Option E, `bunzip2 archive.bz2`, is not correct because it decompresses the bzip2 file to disk, again performing extraction instead of just viewing the contents.

Answer

gunzip archive.gz

Answer

bunzip2 archive.bz2

Question 13

A system administrator is troubleshooting a performance issue. They need to identify which process is consuming the most CPU time over the last 24 hours. Which command should be used?

Accepted Answer

ps aux --sort=-%cpu. The most appropriate among the given choices because `ps aux --sort=-%cpu` lists all processes sorted by the current CPU usage percentage. While this shows a snapshot of current CPU consumption, the `%cpu` field represents the percentage of CPU time used since the process started, giving an approximation of the process's cumulative CPU usage. For historical data over the last 24 hours, process accounting (e.g., `sa` command) would be needed, but among the options, only A provides per-process CPU data.

Answer

sar -u -f /var/log/sa/sa$(date +%d)

Answer

top -b -n1

Answer

uptime

Question 14

A developer needs to extract the third column from a CSV file where columns are separated by commas, but some fields contain commas within double quotes. Which command correctly handles this?

Accepted Answer

awk 'BEGIN { FPAT = "[^,]*|\"[^\"]+\"" } { print $3 }' file.csv. It uses `awk` with the `FPAT` variable to define a field pattern that correctly handles commas inside double-quoted fields. The pattern `[^,]*|"[^"]+"` matches either a sequence of non-comma characters or a double-quoted string (including any commas within it), ensuring that the third column is extracted accurately even when fields contain embedded commas.

Answer

cut -d',' -f3 file.csv

Answer

awk -F',' '{ print $3 }' file.csv

Answer

sed 's/[^,]*,[^,]*,$[^,]*$.*/\1/' file.csv

Question 15

A security policy requires that all users in the 'webadmin' group should have read and write access to files in /var/www/html. New files created in that directory should automatically be assigned to the 'webadmin' group and have group read/write permissions. Which combination of permissions and group ownership should be set on /var/www/html?

Accepted Answer

chmod g+s /var/www/html; chmod 2775 /var/www/html; chown root:webadmin /var/www/html. Setting the setgid bit (g+s) on /var/www/html ensures that new files inherit the directory's group ('webadmin'), and the 2775 permissions grant group read/write/execute (rwx) while the setgid bit is represented by the leading 2. This combination satisfies the security policy: group ownership inheritance and group read/write access for all new files.

Answer

chmod o+t /var/www/html; chmod 1775 /var/www/html; chown root:webadmin /var/www/html

Answer

chmod g+s /var/www/html; chmod 2755 /var/www/html; chown root:webadmin /var/www/html

Answer

chmod u+s /var/www/html; chown root:webadmin /var/www/html