EX200 Practice Questions 1 — 50 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

Question 11

A developer needs to search for the string 'ERROR' in all files under /var/log, but wants to exclude files ending with '.gz'. Which command is correct?

Accepted Answer

grep -r --exclude='*.gz' 'ERROR' /var/log. `grep -r` performs a recursive search through all files under /var/log, and the `--exclude='*.gz'` option tells grep to skip any files matching the glob pattern '*.gz'. This combination ensures that only non-compressed log files are searched for the string 'ERROR', meeting the requirement exactly.

Option B uses `-R` instead of `-r`. In GNU grep, `-R` implies `--dereference-recursive`, which follows symbolic links into other directories. This could lead to searching outside `/var/log` if any symlinks point elsewhere, making it less precise for the stated requirement. While `-r` and `-R` are often conflated, `-R` is not equivalent to `-r` when symlinks are present, and the standard recursive option is `-r`. Therefore, B is incorrect.

Answer

grep -R --exclude='*.gz' 'ERROR' /var/log

Answer

grep -l 'ERROR' /var/log/*.gz

Answer

grep -v '*.gz' -r 'ERROR' /var/log

Question 12

A Red Hat Enterprise Linux server has been configured with a custom repository for offline updates. The administrator runs 'yum repolist' and the custom repository is not listed. Which command should be used to verify that the repository configuration file is valid and located in the correct directory?

Accepted Answer

cat /etc/yum.repos.d/custom.repo. The most direct way to verify that a repository configuration file is valid and located in the correct directory is to check its presence and syntax using 'cat /etc/yum.repos.d/custom.repo'. The repository configuration files must reside in /etc/yum.repos.d/ and have a .repo extension; if the file is missing or malformed, 'yum repolist' will not list the repository. This command simply reads the file, allowing the administrator to confirm its location and inspect its contents for errors.

Answer

yum repoinfo

Answer

yum check-repo

Answer

yum-config-manager --dump

Question 13

The administrator wants to mount a new filesystem on /dev/sdb1 with the label 'backup' and mount it at /mnt/backup. Which commands achieve this?

Accepted Answer

mkfs.xfs /dev/sdb1 && xfs_admin -L backup /dev/sdb1 && mount -L backup /mnt/backup. Both options B and C correctly create an XFS filesystem with the label 'backup' on /dev/sdb1 and mount it to /mnt/backup. Option B uses mkfs.xfs, then sets the label with xfs_admin, then mounts by label (mount -L works without fstab). Option C creates the filesystem with the label in one step and mounts by device path. Options A and D are incorrect: A includes an unnecessary parted command and uses ext4? Actually A creates an XFS partition but then mounts? Wait A: parted ... mkpart primary xfs ... && mkfs.xfs -L backup /dev/sdb1. It doesn't mount, so incomplete. D uses ext4, not XFS. Thus B and C are both valid.

Answer

parted /dev/sdb mkpart primary xfs 0% 100% && mkfs.xfs -L backup /dev/sdb1

Answer

mkfs.ext4 -L backup /dev/sdb1 && echo '/dev/sdb1 /mnt/backup ext4 defaults 0 0' >> /etc/fstab

Question 14

Refer to the exhibit. A container named 'db' is running on the host. An administrator runs `podman inspect db` and sees the above output snippet. What can be concluded about the container's network configuration?

Accepted Answer

The container's port 3306 is bound to all host interfaces.. The output snippet from `podman inspect db` shows `"Ports": {"3306/tcp": [{"HostIp": "0.0.0.0", "HostPort": "3306"}]}`. This indicates that the container's port 3306 is mapped to port 3306 on all host interfaces (0.0.0.0), which is the default bridge networking port binding behavior. Therefore, option C is correct.

Answer

The container is using host networking mode.

Answer

The container cannot be reached from other containers.

Answer

The container is using bridge networking with a static IP.

Question 15

A database server experiences high disk I/O wait times. The administrator runs 'iostat -x 1' and sees that the avgqu-sz for /dev/sda is 25 and await is 200 ms. The disk is a single 7200 RPM SATA drive. Which action is most likely to improve performance?

Accepted Answer

Replace the drive with an SSD or add additional drives in RAID 10. The high avgqu-sz (25) and await (200 ms) indicate the single 7200 RPM SATA drive is saturated, as its maximum IOPS is typically around 75-100 random I/O operations per second. Replacing it with an SSD (which can handle thousands of IOPS) or adding drives in RAID 10 (which increases IOPS through parallelism) directly addresses the hardware bottleneck. No software tuning can overcome the physical limitations of a single spinning disk under heavy I/O load.

Answer

Increase the read-ahead buffer using blockdev --setra

Answer

Change the I/O scheduler from CFQ to noop

Answer

Run 'fsck -f' on the filesystem to check for fragmentation

Question 16

A system administrator has created a new group named 'ops'. The administrator wants to add the existing user 'alice' to this group as a supplementary group without affecting her current group memberships. Which command should be used?

Accepted Answer

usermod -aG ops alice. The `-a` (append) flag combined with `-G` (supplementary groups) in `usermod` adds the user 'alice' to the 'ops' group without removing her from any existing supplementary groups. Without `-a`, the `-G` flag alone would replace the user's current supplementary group list with only the specified groups, which would remove her from any other groups she already belongs to.

Answer

usermod -G ops alice

Answer

groupadd ops alice

Answer

usermod -g ops alice

Question 17

Refer to the exhibit. An administrator wants to mount /dev/sdc1 on /mnt/storage. What must be done first?

Accepted Answer

Create a partition on /dev/sdc. The exhibit shows that /dev/sdc has no partition table (it is a raw disk). Before you can mount a filesystem on /dev/sdc1, you must first create a partition on /dev/sdc using a tool like fdisk or parted. Without a partition, the block device /dev/sdc1 does not exist, so any mount attempt would fail with a 'no such device' error.

Answer

Mount /dev/sdc directly

Answer

Add an entry to /etc/fstab

Answer

Run mkfs.xfs /dev/sdc1

Question 18

An administrator wants to mount an existing ext4 filesystem from /dev/sdb1 to /mnt/data at boot time. What entry should be added to /etc/fstab?

Accepted Answer

/dev/sdb1  /mnt/data  ext4  defaults  0  0. It specifies the correct device (/dev/sdb1), the correct mount point (/mnt/data), the correct filesystem type (ext4), and the correct mount options (defaults) for an ext4 filesystem to be mounted at boot. The /etc/fstab entry must include all six fields in order: device, mount point, filesystem type, options, dump, and pass.

Answer

/dev/sdb1  /mnt/data  xfs  defaults  0  0

Answer

LABEL=data  ext4  defaults  0  0

Answer

/dev/sdb1  /data  ext4  defaults  0  0

Question 19

A system administrator is configuring a new RHEL 9 server with two 500GB SSDs. The requirement: create a 200GB XFS filesystem for /srv/data that is resilient to disk failure. The admin decides to create a RAID 1 (mirror) using mdadm with partitions on each disk: /dev/sda1 and /dev/sdb1, each 200GB. He creates the partitions with fdisk, then runs: mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1. The array is created and synced. He then creates a physical volume, volume group, and logical volume on top of /dev/md0, formats with XFS, and mounts. Later, a disk fails. After replacing the failed disk, he recreates the partition with identical size and runs: mdadm /dev/md0 --add /dev/sdb1. The command fails with 'Device /dev/sdb1 is busy'. What is the most likely cause?

Accepted Answer

The kernel still sees the old partition table; need to run partprobe to reread the partition table.. After replacing a failed disk and recreating the partition, the kernel's in-memory partition table still reflects the old state. The `mdadm --add` command fails with 'Device busy' because the kernel sees the old partition layout and may still hold references to the old partition. Running `partprobe` (or `partx -a`) forces the kernel to reread the partition table from the disk, clearing the stale state and allowing the new partition to be added to the RAID array.

Answer

The replacement disk was not initialized with an mdadm superblock before adding.

Answer

The /dev/md0 array is still in a clean state and does not need the disk yet.

Answer

The /dev/sdb1 partition is already part of another md array.

Question 20

A server uses firewalld with the default zone set to 'drop'. SSH is allowed only for the 192.168.1.0/24 subnet via a rich rule in the 'internal' zone. After a reboot, SSH connections from that subnet are refused. What is the most likely cause?

Accepted Answer

The network interface is not assigned to the 'internal' zone.. After a reboot, firewalld applies the default zone to all interfaces not explicitly assigned to another zone. Since the rich rule allowing SSH from 192.168.1.0/24 is defined in the 'internal' zone, the network interface must be assigned to that zone for the rule to take effect. If the interface is not assigned (e.g., it remains in the default 'drop' zone), all incoming traffic, including SSH from the allowed subnet, is dropped by default.

Answer

The subnet 192.168.1.0/24 is not a valid source for rich rules.

Answer

The rich rule was not made permanent.

Answer

The SSH service is not enabled in the default zone.