EX200 Quick Quiz — 10 Questions

Question 1

A system administrator needs to create a shell script that checks if the user 'jdoe' exists in the system and, if not, creates the user with a home directory. The script should also verify that the creation was successful. Which of the following script snippets correctly implements this logic?

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

Accepted Answer

if id 'jdoe' &>/dev/null; then echo 'Exists'; else useradd -m 'jdoe' && echo 'Created' || echo 'Failed'; fi. It uses `id` to check for the user's existence (redirecting output to /dev/null to suppress messages), then uses `useradd -m` to create the user with a home directory. The `&&` and `||` operators ensure that success or failure of the creation is explicitly reported, fulfilling the requirement to verify successful creation.

Answer

if grep -q '^jdoe:' /etc/passwd; then echo 'Exists'; else useradd 'jdoe' && echo 'Created'; fi

Answer

if ! id 'jdoe' &>/dev/null; then useradd -m 'jdoe'; else echo 'Exists'; fi

Answer

[ -z $(id 'jdoe' 2>/dev/null) ] && useradd -m 'jdoe' && echo 'Created'

Question 2

A system administrator needs to restore the default SELinux security context on all files under /var/www/html after a misconfiguration. Which command should be used?

Accepted Answer

restorecon -R /var/www/html. The `restorecon -R /var/www/html` command restores the default SELinux security contexts on all files under /var/www/html by reading the file contexts defined in the SELinux policy (typically from /etc/selinux/targeted/contexts/files/file_contexts). The `-R` flag ensures recursive operation, making it the correct tool to fix misconfigured contexts without manually specifying a type.

Answer

setfiles -R /var/www/html

Answer

fixfiles -R /var/www/html

Answer

chcon -R -t httpd_sys_content_t /var/www/html

Question 3

A storage administrator is asked to increase the size of an ext4 filesystem mounted at /data. The underlying logical volume /dev/mapper/vg01-lv01 is currently 10GB and the volume group has 5GB of free extents. After extending the logical volume by 2GB using lvextend -L +2G /dev/mapper/vg01-lv01, what command must be run to resize the filesystem?

Accepted Answer

resize2fs /dev/mapper/vg01-lv01. After extending the logical volume with `lvextend`, the filesystem does not automatically recognize the new space. For ext4 filesystems, the `resize2fs` command must be run to resize the filesystem to use the additional logical volume capacity. This command can be executed online (while the filesystem is mounted) and will expand the filesystem to fill the available space in the logical volume.

Answer

lvextend -r -L +2G /dev/mapper/vg01-lv01

Answer

xfs_growfs /data

Answer

fsck -f /dev/mapper/vg01-lv01

Question 4

An administrator wants to add the user 'jane' to the supplementary groups 'wheel' and 'docker' without removing her from other groups. Which command should be used?

Accepted Answer

usermod -aG wheel,docker jane. Both `usermod -aG wheel,docker jane` and `usermod -a -G wheel,docker jane` are valid commands to append the user to the specified supplementary groups without removing her from other groups. The `-a` (append) flag can be combined with `-G` as `-aG` or provided separately (`-a -G`); both forms work identically. Option D (`usermod -G`) without `-a` would overwrite all supplementary groups, which is incorrect. Option A uses `groupmems`, which is not the standard command for this task and has incorrect syntax.

Answer

groupmems -a jane -g wheel,docker

Answer

usermod -G wheel,docker jane

Question 5

A server's firewall is managed by firewalld. The admin adds a rule to allow HTTPS traffic to the public zone, but clients still cannot connect. What is the most likely cause?

Accepted Answer

The rule was added with --permanent but firewall-cmd --reload was not run.. When a rule is added with the `--permanent` flag in firewalld, it is written to the configuration files but not applied to the runtime firewall. Until `firewall-cmd --reload` is executed, the runtime configuration remains unchanged, so the new rule allowing HTTPS traffic is not active. Clients cannot connect because the firewall is still blocking HTTPS based on the old runtime rules.

Answer

The rule must be added as a rich rule, not a simple service.

Answer

The default zone is not set to public.

Answer

firewalld is just a wrapper for iptables, so iptables rules must be cleared.

Question 6

Which TWO commands can be used to display available disk space on mounted filesystems in a human-readable format?

Accepted Answer

df -h. The `df -h` command displays disk space usage for mounted filesystems, with the `-h` flag converting sizes into human-readable units (e.g., KB, MB, GB). This directly meets the requirement of showing available disk space on mounted filesystems in a human-readable format. The `du -sh` command shows the total disk usage of a specific directory or file, not available space on filesystems, so it does not satisfy the question's requirement.

Answer

blkid

Answer

ls -lh

Answer

du -sh

Answer

fdisk -l

Question 7

A system administrator wants to find all files in /var that are larger than 100MB and have been modified within the last 7 days. The output should be a list of file paths with sizes in human-readable format, sorted by size descending. Which command pipeline accomplishes this?

Accepted Answer

find /var -type f -size +100M -mtime -7 -exec du -h {} + | sort -rh. It uses `find` with `-size +100M` and `-mtime -7` to match files larger than 100MB modified within 7 days, then `-exec du -h {} +` aggregates sizes in human-readable format, and `sort -rh` sorts by the first field (size) in reverse human-numeric order, producing the required descending list.

Answer

find /var -type f -size +100M -mtime -7 -ls | sort -k7 -n

Answer

find /var -type f -size +100M -mtime -7 -exec ls -lh {} \; | sort -k5 -h

Answer

find /var -type f -size +100M -mtime -7 -printf '%s %p
' | sort -n -r | head -20

Question 8

A system administrator needs to create a shell script that processes a list of hostnames stored in a file, one per line, and runs a command on each host. Which loop construct is most appropriate?

Accepted Answer

while read host; do ... done < hosts. The `while read host; do ... done < hosts` construct reads the file line by line, preserving each hostname exactly as it appears, including spaces or special characters. This is the safest and most idiomatic way to process a list of hostnames in a shell script, as it avoids word splitting and glob expansion issues that can occur with other methods.

Answer

for i in $(seq 1 $(wc -l < hosts)); do ... done

Answer

for host in $(cat hosts); do ... done

Answer

until read host; do ... done < hosts

Question 9

A developer wants to create a script that accepts a directory path as an argument and creates a timestamped backup of that directory. If no argument is provided, it should back up the current directory. How should the script handle the argument?

Accepted Answer

dir=${1:-.}. `${1:-.}` uses the default value substitution syntax in bash: if parameter `$1` (the first positional argument) is unset or null, it expands to `.` (the current directory). This ensures the script backs up the supplied directory path or defaults to the current directory when no argument is provided, exactly matching the requirement.

Answer

dir=${@:-.}

Answer

dir=${0:-.}

Answer

dir=${?:-.}

Question 10

A Red Hat Enterprise Linux 9 system enforces a security policy that user accounts must be disabled after 90 days of inactivity. The system administrator has configured /etc/shadow accordingly with the proper fields. User 'bob' has been on leave for 95 days. When bob returns and tries to log in, he is unable to do so. The administrator checks the shadow file and sees that bob's password expiration date has passed and the account is locked due to inactivity (the inactivity period has exceeded). The administrator wants to immediately reactivate bob's account without changing the password, and also wants to set the account to expire in 30 days from now (relative to the current date). Which set of commands should the administrator run to achieve this goal?

Accepted Answer

chage -E $(date -d +30days +%Y-%m-%d) bob; chage -I -1 bob. `chage -E $(date -d +30days +%Y-%m-%d) bob` sets the account expiration date to 30 days from now, and `chage -I -1 bob` disables the inactivity period (sets it to -1, meaning no inactivity lockout), which immediately reactivates the account without changing the password. This directly addresses the requirement to unlock the account (which was locked due to exceeding the inactivity period) and set a new expiration date.

Answer

usermod -e 2024-12-31 bob; passwd -S bob

Answer

chage -d 0 bob; usermod -L bob

Answer

usermod -e $(date -d +30days +%Y-%m-%d) bob; passwd -u bob