220-1202 Linux Commands and File Permissions — Timed 20 Questions

Question 1

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?

Accepted Answer

chmod 644 /etc/passwd. 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.

Answer

chmod 600 /etc/passwd

Answer

chmod 755 /etc/passwd

Answer

chmod 444 /etc/passwd

Question 2

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?

Accepted Answer

find /var/log -mtime -1. 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.

Answer

find /var/log -atime -1

Answer

find /var/log -ctime -1

Answer

find /var/log -mmin -1440

Question 3

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?

Accepted Answer

find / -name notes.txt. 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.

Answer

locate notes.txt

Answer

grep notes.txt /

Answer

find ~ -name notes.txt

Question 4

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?

Accepted Answer

chmod o+w /opt/app. 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.

Answer

chmod 777 /opt/app

Answer

chown user:user /opt/app

Answer

chmod g+w /opt/app

Question 5

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?

Accepted Answer

chmod 600 /etc/app/config.cfg. 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.

Answer

chmod 777 /etc/app/config.cfg

Answer

chmod 644 /etc/app/config.cfg

Answer

chmod 400 /etc/app/config.cfg

Question 6

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?

Accepted Answer

chgrp staff file. 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.

Answer

chmod 755 file

Answer

chmod g+r file

Answer

chown user:staff file

Question 7

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?

Accepted Answer

usermod -aG www-data www-data. 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.

Answer

chmod g+rx /var/www/html

Answer

chmod o+rx /var/www/html

Answer

chown www-data:www-data /var/www/html

Question 8

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?

Accepted Answer

find / -type f -perm -4000. 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.

Answer

find / -type f -perm 0777

Answer

find / -type f -perm 4000

Answer

find / -type f -perm /4000

Question 9

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?

Accepted Answer

chmod u+x script.sh. 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.

Answer

chmod 755 script.sh

Answer

chmod 644 script.sh

Answer

chown user:user script.sh

Question 10

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?

Accepted Answer

find /usr/bin -user root -perm /6000. 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.

Answer

find /usr/bin -user root -perm -6000

Answer

find /usr/bin -user root -perm 4000 -o -perm 2000

Answer

ls -la /usr/bin | grep '^...s'

Question 11

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?

Accepted Answer

chgrp appgroup config.cfg && chmod g+w config.cfg. 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.

Answer

chmod 666 config.cfg

Answer

chown appuser config.cfg

Answer

setfacl -m u:appuser:rw config.cfg

Question 12

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

Accepted Answer

find /var/log -mtime 0. 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.

Answer

ls -la /var/log | grep '24 hours'

Answer

find /var/log -atime 0

Answer

locate /var/log | sort -m

Question 13

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?

Accepted Answer

ls -l /opt/custom/bin/command. 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.

Answer

stat /opt/custom/bin/command

Answer

file /opt/custom/bin/command

Answer

chmod /opt/custom/bin/command

Question 14

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?

Accepted Answer

chmod g+r /opt/app/data. 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.

Answer

chmod o+r /opt/app/data

Answer

chmod 644 /opt/app/data

Answer

chown :developers /opt/app/data

Question 15

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

Accepted Answer

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

Answer

grep -r 'Password' /etc

Answer

find /etc -name '*Password*'

Answer

locate Password | grep /etc

Question 16

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?

Accepted Answer

chgrp -R datagroup /srv/data. 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.

Answer

chown datagroup: /srv/data

Answer

chmod -R g+rw /srv/data

Answer

groupmod -R datagroup /srv/data

Question 17

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?

Accepted Answer

cp -p /backup/script.sh /usr/local/bin/. 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.

Answer

mv /backup/script.sh /usr/local/bin/

Answer

cp /backup/script.sh /usr/local/bin/

Answer

rsync -a /backup/script.sh /usr/local/bin/

Question 18

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?

Accepted Answer

chmod u+x script.sh. 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).

Answer

chmod 755 script.sh

Answer

chmod +r script.sh

Answer

chmod 644 script.sh

Question 19

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

Accepted Answer

useradd -m jdoe && passwd jdoe. 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.

Answer

adduser jdoe

Answer

useradd jdoe && passwd jdoe

Answer

usermod -m jdoe

Question 20

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?

Accepted Answer

lsof /path/to/script. 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.

Answer

fuser /path/to/script

Answer

ps aux | grep script

Answer

strace -p $(pgrep script)