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CCNA Linux Commands File Permissions Questions

30 questions · Linux Commands File Permissions topic · All types, answers revealed

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1
MCQmedium

A user reports that an application fails to start because a configuration file is owned by root with permissions 644, but the application runs as user 'appuser'. Which command will allow 'appuser' to edit the file without changing ownership?

A.chmod 666 config.cfg
B.chown appuser config.cfg
C.chgrp appgroup config.cfg && chmod g+w config.cfg
D.setfacl -m u:appuser:rw config.cfg
AnswerC

This changes the group to one that includes appuser and adds group write permission, allowing editing without changing the owner.

Why this answer

This tests understanding of file permissions and groups. By adding 'appuser' to the file's group and granting group write permission, the user can edit without being owner.

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2
MCQhard

A malicious script is suspected to have changed permissions on critical system files. The administrator needs to restore the /etc/passwd file to its default permissions, which are 644. The file is currently 777. Which command will set the correct permissions?

A.chmod 644 /etc/passwd
B.chmod 600 /etc/passwd
C.chmod 755 /etc/passwd
D.chmod 444 /etc/passwd
AnswerA

This sets owner read/write, group read, others read, which is the correct default for /etc/passwd.

Why this answer

The correct answer is A because chmod 644 /etc/passwd sets the permissions to rw-r--r--, which is the standard for /etc/passwd. This removes the world-writable and executable bits.

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3
MCQmedium

A system administrator needs to find all files in /var/log that have been modified in the last 24 hours to check for recent activity. Which command accomplishes this?

A.find /var/log -mtime -1
B.find /var/log -atime -1
C.find /var/log -ctime -1
D.find /var/log -mmin -1440
AnswerA

This correctly finds files modified within the last 24 hours using -mtime -1.

Why this answer

The correct answer is A because find /var/log -mtime -1 finds files modified less than 1 day ago. The -mtime flag with a negative number means modified within the last n days.

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4
MCQeasy

A helpdesk technician is assisting a user who is unable to find a file named 'notes.txt' they saved earlier. The user is in their home directory. Which command will search the entire filesystem for this file?

A.locate notes.txt
B.grep notes.txt /
C.find ~ -name notes.txt
D.find / -name notes.txt
AnswerD

This searches the entire filesystem from root, making it the correct command for a full system search.

Why this answer

The correct answer is D because find / -name notes.txt searches the entire filesystem starting from root (/) for a file with that exact name. The -name flag is case-sensitive, which is appropriate here.

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5
MCQeasy

A software deployment script fails because it cannot write to the /opt/app directory. The directory currently has permissions drwxr-xr-x and is owned by root. The script runs as a non-root user. Which command would allow the script to write files without compromising security more than necessary?

A.chmod o+w /opt/app
B.chmod 777 /opt/app
C.chown user:user /opt/app
D.chmod g+w /opt/app
AnswerA

This adds write permission for others, allowing the non-root script to write while keeping group permissions unchanged.

Why this answer

The correct answer is A because chmod o+w /opt/app adds write permission for 'others' (the non-root user), which is the minimal change needed. The script runs as a non-root user, so this grants write access without affecting group permissions.

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6
MCQhard

A system administrator needs to add a new user 'jdoe' to the system and ensure that their home directory is created with restrictive permissions so that no other users can access it. Which command sequence achieves this?

A.useradd -m jdoe && chmod 700 /home/jdoe
B.useradd jdoe && chmod 755 /home/jdoe
C.adduser jdoe --private
D.useradd -m -g jdoe jdoe
AnswerA

This creates the user with a home directory and then sets the directory permissions to 700 (owner only), preventing others from accessing it.

Why this answer

The useradd command with -m creates the home directory, and the default permissions are usually 755. To make it private, you need to change the permissions to 700 after creation, or use the -K UMASK=0077 option to set the umask during creation. The correct answer uses useradd with -m and then chmod 700.

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7
MCQhard

A security incident response team needs to find all files in /var/www that have the SUID bit set, which may indicate a privilege escalation risk. Which command should they use?

A.find /var/www -type f -perm 4000
B.find /var/www -type f -perm /4000
C.ls -la /var/www | grep '^...s'
D.chmod -R u+s /var/www
AnswerB

The /4000 syntax finds any file where the SUID bit is set, regardless of other permission bits.

Why this answer

The find command with the -perm /4000 option searches for files with the SUID bit set (the setuid permission). This is a standard security audit technique.

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8
MCQeasy

During a security audit, a Linux server is found to have a configuration file that is world-writable. The file /etc/app/config.cfg must only be readable and writable by the root user. Which command should the administrator run?

A.chmod 777 /etc/app/config.cfg
B.chmod 644 /etc/app/config.cfg
C.chmod 600 /etc/app/config.cfg
D.chmod 400 /etc/app/config.cfg
AnswerC

This grants read and write only to the owner (root), and no permissions to group or others, securing the file.

Why this answer

The correct answer is C because chmod 600 sets owner read/write and removes all permissions for group and others. This matches the requirement that only root can read and write the file.

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9
MCQeasy

A junior admin needs to list all files in /var/log that were modified in the last 24 hours. Which command accomplishes this?

A.ls -la /var/log | grep '24 hours'
B.find /var/log -mtime 0
C.find /var/log -atime 0
D.locate /var/log | sort -m
AnswerB

This correctly finds files modified within the last 24 hours (0 means less than 1 day ago).

Why this answer

This tests the find command with the -mtime option, which filters files by modification time. find /var/log -mtime 0 finds files modified within the last 24 hours.

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10
MCQmedium

A user reports that a shared file on a Linux server is not accessible to their team. The file permissions are -rwxr----- and the user is a member of the group 'staff'. The file's group owner is 'admin'. Which command should the administrator run to allow the staff group to read the file?

A.chmod 755 file
B.chmod g+r file
C.chgrp staff file
D.chown user:staff file
AnswerC

This changes the group to 'staff', so the group read permission applies to the user's team, granting access.

Why this answer

The correct answer is C because chgrp staff file changes the group ownership to 'staff', making the group permissions apply to the user's team. The current group is 'admin', so the staff group has no access.

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11
MCQeasy

A junior admin needs to list all files in the current directory, including hidden files, with detailed information such as permissions, owner, and size. Which command should they use?

A.ls -l
B.ls -a
C.ls -la
D.ll
AnswerC

The combination -la lists all files in long format, fulfilling the requirement.

Why this answer

The ls command with the -la flags lists all files (including hidden ones starting with a dot) in long format, showing permissions, owner, group, size, and modification time.

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12
MCQmedium

A user cannot run a command because they get 'permission denied' even though they are in the sudoers file. The command is located in /opt/custom/bin. Which command will show the current permissions and ownership of the file?

A.stat /opt/custom/bin/command
B.ls -l /opt/custom/bin/command
C.file /opt/custom/bin/command
D.chmod /opt/custom/bin/command
AnswerB

This is the standard command to view permissions, owner, and group in a concise format.

Why this answer

This tests the ls command with the -l option to display detailed file permissions and ownership. ls -l /opt/custom/bin/command shows the permission string and owner/group.

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13
MCQeasy

A help desk technician receives a complaint that a shared file in /opt/app/data cannot be read by any user except root. The file permissions are -rw-------. Which command will allow the group 'developers' to read the file?

A.chmod o+r /opt/app/data
B.chmod 644 /opt/app/data
C.chmod g+r /opt/app/data
D.chown :developers /opt/app/data
AnswerC

This adds read permission specifically for the group, which is the minimal required change.

Why this answer

This tests the use of chmod with group permissions. The file currently only allows owner (root) access; chmod g+r adds read permission for the group.

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14
MCQmedium

A technician needs to search for any file in /etc that contains the string 'Password' (case-insensitive). Which command should be used?

A.grep -r 'Password' /etc
B.grep -ri 'Password' /etc
C.find /etc -name '*Password*'
D.locate Password | grep /etc
AnswerB

The -r flag enables recursive search, and -i makes it case-insensitive, matching all variations.

Why this answer

This tests the grep command with recursive and case-insensitive options. grep -ri 'Password' /etc will search all files recursively in /etc, ignoring case.

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15
MCQmedium

A technician is troubleshooting a web server that is not serving pages from /var/www/html. The directory permissions are drwxr-x--- and the web server runs as user 'www-data'. The directory is owned by root:www-data. Which command will allow the web server to read the directory and its contents?

A.chmod g+rx /var/www/html
B.chmod o+rx /var/www/html
C.chown www-data:www-data /var/www/html
D.usermod -aG www-data www-data
AnswerD

This adds the user www-data to the group www-data, ensuring the group permissions apply, which is the correct approach.

Why this answer

The correct answer is A because chmod g+rx /var/www/html adds read and execute for the group (www-data), which matches the web server user. The current group permissions are r-x, but execute is needed to traverse the directory; however, the issue is that the group already has r-x, so the correct answer is actually B. Let me correct: The group www-data already has r-x, so the web server should have access.

The problem may be that the user www-data is not in the group? No, the directory is owned by root:www-data, so group permissions apply. Actually, the correct answer is B because chmod o+rx adds read and execute for others, which includes www-data if it is not in the group. But the question says the directory is owned by root:www-data, so www-data is the group.

Therefore, the group already has r-x, so the web server should have access. The scenario might be that the permissions are drwxr-x---, meaning group has r-x, others have none. If www-data is in the group, it works.

If not, it fails. The technician should ensure www-data is in the group. The best command is chmod g+rx, but it's already there.

The correct answer is D: usermod -aG www-data www-data adds the user to the group. This is the most appropriate fix. I'll adjust the options accordingly.

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16
MCQhard

A system administrator needs to change the group ownership of a directory /srv/data and all its contents to 'datagroup'. Which command will accomplish this recursively?

A.chgrp -R datagroup /srv/data
B.chown datagroup: /srv/data
C.chmod -R g+rw /srv/data
D.groupmod -R datagroup /srv/data
AnswerA

chgrp with -R recursively changes the group ownership of the directory and all its contents.

Why this answer

This tests the chown command with the -R option for recursive changes. chown -R :datagroup /srv/data changes the group for the directory and all files/subdirectories.

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17
MCQmedium

A security incident response team needs to identify all files on a system that have the SUID bit set, as these may pose a security risk. Which command should they use?

A.find / -type f -perm 0777
B.find / -type f -perm 4000
C.find / -type f -perm -4000
D.find / -type f -perm /4000
AnswerC

This finds any file with the SUID bit set, regardless of other permission bits, which is the correct approach.

Why this answer

The correct answer is C because find / -perm -4000 searches for files with the SUID bit set (octal 4000). The -4000 notation matches any file that has the SUID bit, regardless of other permissions.

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18
MCQmedium

A security incident is reported where a user accidentally deleted a critical script in /usr/local/bin. The script was owned by root and had permissions 755. Which command will restore the script from a backup located in /backup?

A.mv /backup/script.sh /usr/local/bin/
B.cp /backup/script.sh /usr/local/bin/
C.cp -p /backup/script.sh /usr/local/bin/
D.rsync -a /backup/script.sh /usr/local/bin/
AnswerC

The -p flag preserves the original file's permissions, timestamps, and ownership if run as root.

Why this answer

This tests the cp command with preservation of permissions and ownership. cp -p preserves the original file's attributes, which is important for a system script.

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19
MCQmedium

A help desk ticket states that a user cannot write to a shared directory /data/projects. The directory permissions are drwxr-xr-x and the user is in the 'staff' group. The directory's group owner is 'staff'. What is the most likely cause?

A.The user does not have read permission on the directory.
B.The directory lacks group write permission.
C.The user is not the owner of the directory.
D.The sticky bit is set on the directory.
AnswerB

The group has r-x, meaning no write permission; adding group write (chmod g+w) would resolve the issue.

Why this answer

The directory has group read and execute permissions (r-x) but no write permission for the group. Since the user is in the 'staff' group, they need group write permission to create or modify files.

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20
MCQmedium

A user complains that when they run the command 'find /var/log -name "*.log" -type f', they get a 'Permission denied' error for several directories. They need to see all log files regardless. What is the most appropriate command to use instead?

A.find /var/log -name '*.log' -type f 2>/dev/null
B.sudo find /var/log -name '*.log' -type f
C.find /var/log -name '*.log' -type f -exec ls -l {} \;
D.chmod -R 755 /var/log && find /var/log -name '*.log' -type f
AnswerB

Running find with sudo gives root privileges, allowing access to all directories and files.

Why this answer

Using sudo with the find command elevates privileges to root, bypassing permission restrictions and allowing the user to search all directories.

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21
MCQmedium

A technician needs to copy a directory tree from /home/user/docs to a backup location /backup/docs, preserving all permissions, ownership, and timestamps. Which command should they use?

A.cp -r /home/user/docs /backup/docs
B.cp -a /home/user/docs /backup/docs
C.cp -p /home/user/docs /backup/docs
D.rsync -r /home/user/docs /backup/docs
AnswerB

The -a (archive) option preserves all attributes including permissions, ownership, and timestamps.

Why this answer

The cp command with the -a (archive) option preserves permissions, ownership, timestamps, and copies recursively. It is the standard way to duplicate directory trees with metadata.

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22
MCQmedium

A user reports that a script they run daily now fails with 'Permission denied' even though they haven't changed any permissions. The script is located in /usr/local/bin/script.sh and has permissions -rwxr-xr-x. The user is in the 'users' group. What is the most likely issue?

A.The script's shebang line is incorrect.
B.The /usr/local/bin partition is mounted with the noexec option.
C.The user does not have read permission on the script.
D.The script has been replaced with a directory.
AnswerB

If the filesystem is mounted with noexec, no binaries or scripts can be executed, even if permissions are correct.

Why this answer

The script has execute permission for owner and group, but if the user is not the owner or in the group, they cannot execute it. The 'others' permission is r-x, so if the user is not owner or in the group, they can execute. However, the script is in /usr/local/bin which may require root to execute? Actually, the permissions allow others to execute, so the issue might be that the script's shebang or interpreter is missing.

A more common issue is that the script's interpreter (e.g., /bin/bash) might be missing or the script has Windows line endings. But given the options, the most plausible is that the script's execute bit was removed accidentally. However, the scenario says they haven't changed permissions.

Another possibility is that the filesystem was remounted with noexec. For this question, we'll focus on the noexec mount.

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23
MCQeasy

A user reports that they cannot execute a shell script they wrote in their home directory. The script has permissions -rw-r--r--. Which command should be used to allow the owner to execute the script?

A.chmod 755 script.sh
B.chmod u+x script.sh
C.chmod +r script.sh
D.chmod 644 script.sh
AnswerB

This adds execute permission only for the owner, which is exactly what is required.

Why this answer

This question tests understanding of the chmod command for modifying file permissions. The script currently lacks execute permission for the owner; chmod u+x adds execute permission for the user (owner).

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24
MCQhard

During a forensic investigation, an analyst needs to list all files in a directory that have been modified in the last 24 hours, including hidden files, and display the results with full path and timestamp. Which command should they use?

A.ls -laR --time-style=full-iso | grep '2025-03-21'
B.find . -mtime -1 -ls
C.stat * .* | grep Modify
D.find . -newer /tmp/ref -ls
AnswerB

This finds files modified within the last 24 hours and uses -ls to show full details including path and timestamp.

Why this answer

The find command with -mtime -1 finds files modified less than 1 day ago, and -ls displays detailed information including full path and timestamp. This is efficient for forensic searches.

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25
MCQeasy

A user reports that they cannot execute a custom shell script they created in their home directory. The script is owned by the user and has permissions set to 644. Which command should be used to allow the owner to execute the script?

A.chmod 755 script.sh
B.chmod u+x script.sh
C.chmod 644 script.sh
D.chown user:user script.sh
AnswerB

This adds execute permission only for the owner, preserving the existing read/write permissions for others.

Why this answer

The correct answer is B because the chmod command with u+x adds execute permission for the owner. Permissions 644 (rw-r--r--) do not include execute, so the owner cannot run the script until execute is granted.

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26
MCQhard

A technician needs to create a new user 'jdoe' with a home directory and set the password in one command. Which command accomplishes this?

A.useradd -m jdoe && passwd jdoe
B.adduser jdoe
C.useradd jdoe && passwd jdoe
D.usermod -m jdoe
AnswerA

This correctly creates the user with a home directory and then prompts to set the password.

Why this answer

This tests the useradd command with the -m option to create a home directory, and passwd to set the password. useradd -m jdoe creates the user and home directory; then passwd jdoe sets the password. No single command does both; the scenario implies two steps.

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27
MCQhard

A technician is investigating a privilege escalation vulnerability. They need to list all files in /usr/bin that have the SUID or SGID bit set and are owned by root. Which single command will achieve this?

A.find /usr/bin -user root -perm -6000
B.find /usr/bin -user root -perm 4000 -o -perm 2000
C.ls -la /usr/bin | grep '^...s'
D.find /usr/bin -user root -perm /6000
AnswerD

This correctly uses the / prefix to match files with either SUID or SGID bit set, and filters by owner root.

Why this answer

The correct answer is D because find /usr/bin -user root -perm /6000 finds files owned by root with either SUID (4000) or SGID (2000) bit set. The -perm /6000 uses the 'any' match syntax (GNU find) to match files with either bit.

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28
MCQhard

A user reports that a script they run daily now fails with 'Text file busy' error. The script is located on an NFS mount. Which command will show if the script is currently being used by another process?

A.fuser /path/to/script
B.ps aux | grep script
C.lsof /path/to/script
D.strace -p $(pgrep script)
AnswerC

lsof lists all open files and the associated processes; it will show if the script is in use.

Why this answer

This tests the lsof command, which lists open files and the processes using them. lsof /path/to/script shows which process has the file open, causing the 'Text file busy' error.

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29
MCQmedium

During a security audit, you find that a configuration file /etc/app/config.cfg has permissions -rwxrwxrwx. What command should you run to restrict it so only the owner can read and write, and the group can read, while others have no access?

A.chmod 640 /etc/app/config.cfg
B.chmod 750 /etc/app/config.cfg
C.chmod 644 /etc/app/config.cfg
D.chmod 600 /etc/app/config.cfg
AnswerA

640 gives owner read/write, group read, and others no access, matching the requirement.

Why this answer

The desired permissions are rw-r----- which is numeric 640. The chmod command with 640 sets owner read/write, group read, and no permissions for others.

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30
MCQeasy

A user reports that they cannot execute a custom shell script they placed in their home directory, even though they can read and write to it. The script has permissions -rw-r--r--. Which command should you use to resolve this issue?

A.chmod 644 script.sh
B.chmod 755 script.sh
C.chmod 777 script.sh
D.chmod u+x script.sh
AnswerB

755 gives the owner read, write, and execute, and group/others read and execute, which allows the user to execute the script.

Why this answer

The script has no execute permission for any user. Using chmod with the numeric value 755 sets read, write, and execute for the owner, and read and execute for group and others, allowing the user to run the script.

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