LFCS Essential Commands Practice Test 1 — 15 Questions

Question 1

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. `-size +100M` matches files larger than 100 megabytes (where M stands for mebibytes, 1024*1024 bytes). Option D is correct because `-size +102400k` matches files larger than 100 megabytes (since 100*1024 = 102400 kilobytes). Option B is incorrect because `-size +100000000c` matches files larger than approximately 95.4 MB (100,000,000 bytes), not 100 MB. Option C is incorrect because `MB` is not a valid size suffix in find. Option E is incorrect because it omits the `+` sign, matching files exactly 100 MB rather than larger than 100 MB.

Answer

find /home -type f -size +100000000c

Answer

find /home -type f -size +100MB

Answer

find /home -type f -size 100M

Question 2

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. The `chown alice:staff file.txt` command changes both the user owner to `alice` and the group owner to `staff` in a single operation. Option C is correct because `chgrp staff file.txt` changes only the group ownership of the file to `staff`. Option D is incorrect because `usermod -G staff alice` modifies the group membership of the user `alice`, not the ownership of any file.

Answer

chmod 755 file.txt

Answer

usermod -G staff alice

Answer

passwd alice

Question 3

A user reports that a script fails with 'Permission denied' when executed. The script has permissions -rw-r--r-- and is owned by the user. Which command should the user run to make the script executable for the owner only?

Accepted Answer

chmod u+x script.sh. The script currently has permissions `-rw-r--r--`, meaning the owner has read and write but not execute permission. The `chmod u+x` command adds the execute permission for the owner only, which is exactly what the user needs to run the script without affecting group or others.

Answer

chmod u+s script.sh

Answer

chown :users script.sh

Answer

chmod +x script.sh

Question 4

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 -type f -mtime -7. The `find` command with `-mtime -7` searches for files whose modification time (content change) is less than 7 days ago, which matches the requirement of 'modified in the last 7 days'. The `-type f` restricts the search to regular files, and `/var/log` is the target directory.

Answer

find /var/log -type f -atime -7

Answer

find /var/log -type f -ctime -7

Answer

find /var/log -type f -mtime +7

Question 5

An administrator wants to ensure that a background process continues running after logout. Which command should be used to start the process?

Accepted Answer

nohup sleep 100 &. `nohup` allows a process to ignore the SIGHUP signal that is sent to background processes when the parent shell exits, ensuring it continues running after logout. The `&` places the command in the background, and `nohup` redirects output to `nohup.out` by default, making it the standard way to run a process immune to hangups.

Answer

runproc sleep 100 &

Answer

sleep 100 &

Answer

sleep 100 & disown

Question 6

A technician needs to display the contents of a compressed file named archive.tar.gz without extracting it. Which command should be used?

Accepted Answer

zcat archive.tar.gz | tar -t. It uses `zcat` to decompress the `.gz` layer on the fly and pipes the resulting uncompressed tar archive into `tar -t`, which lists the contents without extracting. This allows viewing the file listing without first decompressing to disk, satisfying the requirement to display contents without extraction.

Answer

tar -tf archive.tar

Answer

tar -xzf archive.tar.gz

Answer

zcat archive.tar.gz

Question 7

A user wants to find the location of the 'grep' binary. Which command should they use?

Accepted Answer

which grep. The 'which' command is specifically designed to locate the binary (executable) of a command by searching the directories listed in the user's PATH environment variable. Option B, 'which grep', will output the full path to the grep binary, such as '/usr/bin/grep', directly answering the user's request.

Answer

man grep

Answer

uname -a

Answer

grep -r 'grep' /usr/bin

Question 8

Which TWO commands can be used to create a new empty file?

Accepted Answer

touch file. The `touch` command is specifically designed to create an empty file if it does not already exist, or update its timestamps if it does. Option D is correct because using the shell redirection operator `>` with no command before it (or with a null command) creates an empty file by truncating any existing content or creating a new zero-byte file.

Answer

mkdir file

Answer

cat file

Answer

echo 'text' > file

Question 9

Which THREE commands can be used to view the contents of a file?

Accepted Answer

cat. The `cat` command (option C) is a standard Unix utility that reads files sequentially and outputs their contents to the standard output. It is one of the most basic and direct ways to view the entire content of a file in the terminal.

Answer

grep

Answer

find

Question 10

What is the purpose of the chmod 755 command in this exhibit?

Accepted Answer

Set permissions to rwxr-xr-x. The chmod 755 command sets the file permissions to rwxr-xr-x, meaning the owner has read, write, and execute permissions (7), while the group and others have read and execute permissions (5). This is a common permission set for executable scripts and directories to allow execution without granting write access to non-owners.

Answer

Add execute permission for the owner only

Answer

Remove write permission for others

Answer

Set the setuid bit

Question 11

Based on the exhibit, which process will be affected if the root user runs 'kill 5678'?

Accepted Answer

The www-data process with PID 5678. The 'kill 5678' command sends the default SIGTERM (signal 15) to the process with PID 5678. Since the root user has the CAP_KILL capability and is not subject to the ordinary permission checks that restrict non-root users, root can send signals to any process, including those owned by www-data. Therefore, the www-data process with PID 5678 will be terminated.

Answer

The root process (PID 1234)

Answer

All www-data processes

Answer

No process, because root cannot kill www-data processes

Question 12

A developer accidentally deleted a critical file /var/log/app.log. The system administrator knows that the file was recently backed up using a cron job that runs 'tar -czf /backup/logs.tar.gz /var/log/'. Which command should the administrator use to restore the file from the backup without extracting the entire archive?

Accepted Answer

tar -xzf /backup/logs.tar.gz --to-stdout var/log/app.log > /var/log/app.log. `tar -xzf` extracts the specified file (`var/log/app.log`) from the compressed archive and `--to-stdout` sends its content to standard output, which is then redirected to recreate the file at `/var/log/app.log`. This restores the single file without extracting the entire archive, matching the requirement precisely.

Answer

tar -xf /backup/logs.tar.gz var/log/app.log

Answer

tar -tf /backup/logs.tar.gz | grep app.log

Answer

cp /backup/logs.tar.gz:/var/log/app.log /var/log/app.log

Question 13

A system administrator needs to find all files in /home that are owned by user 'alice' and have been modified in the last 7 days. The administrator then wants to compress those files into a single archive named alice_recent.tar.gz. Which of the following commands accomplishes this?

Accepted Answer

tar -czf alice_recent.tar.gz -T <(find /home -user alice -mtime -7). It uses `tar -czf` with process substitution to compress the files found by `find` into a gzipped tar archive named alice_recent.tar.gz. The `-z` flag enables gzip compression, and `-T <(...)` reads the list of files from the process substitution, which runs `find` to locate files owned by alice modified within the last 7 days. Options A, B, and D either do not compress or use incompatible formats.

Answer

find /home -user alice -mtime -7 -exec tar -rf alice_recent.tar.gz {} +

Answer

find /home -user alice -mtime -7 -print | cpio -o > alice_recent.tar.gz

Answer

find /home -user alice -mtime -7 | tar -cvf alice_recent.tar.gz

Question 14

A junior administrator needs to display the first 10 lines of a file named 'data.csv'. Which command should they use?

Accepted Answer

head data.csv. The `head` command is specifically designed to display the first 10 lines of a file by default. Running `head data.csv` will output the first 10 lines of the CSV file, making it the correct choice for this task.

Answer

less data.csv

Answer

tail data.csv

Answer

cat data.csv

Question 15

A system administrator is troubleshooting a user's report that a command 'myapp' is not found. The administrator checks the PATH variable and sees it includes /usr/local/bin. The administrator verifies that the binary 'myapp' exists in /usr/local/bin with permissions 755. However, running 'myapp' still fails with 'command not found'. What is the most likely cause?

Accepted Answer

The shell's hash table is stale; run 'hash -r'. The shell caches the locations of executables in a hash table to avoid searching PATH repeatedly. When a new binary is added to a directory already in PATH, the shell may still have a stale entry (or no entry) for that command, causing it to report 'command not found' even though the binary exists. Running 'hash -r' clears the entire hash table, forcing the shell to re-scan PATH on the next invocation.

Answer

The user's PATH does not include /usr/local/bin

Answer

The binary is a shell script missing a shebang

Answer

The binary does not have execute permission for the user