EX200 Hard Questions — 25 Difficult Questions

Question 1

Which TWO methods are considered best practices for securing SSH access to a server? (Select exactly two.)

Accepted Answer

Disable root login by setting PermitRootLogin no.. Disabling root login by setting `PermitRootLogin no` in `/etc/ssh/sshd_config` prevents direct SSH access as the root user, forcing administrators to log in as a regular user and then use `sudo` or `su` to escalate privileges. This reduces the attack surface by eliminating a high-value target for brute-force attacks and ensures all actions are auditable via the regular user's session.

Answer

Use only password authentication for simplicity.

Answer

Change the default SSH port to a high-numbered port.

Answer

Allow SSH access for all users in the system.

Question 2

A system fails to boot with an error about a missing ext4 filesystem. From the rescue environment, which command should be run to attempt automatic repair of all filesystems?

Accepted Answer

fsck -A -y. `fsck -A -y` automatically checks all filesystems listed in `/etc/fstab` (the `-A` flag) and answers 'yes' to any repair prompts (the `-y` flag), making it the most appropriate command for automatic repair of all filesystems from a rescue environment. The error indicates a missing ext4 filesystem, and this command will attempt to repair any ext4 (or other) filesystem issues without manual intervention.

Answer

fsck /dev/sda1

Answer

debugfs -R 'repair'

Answer

e2fsck -p

Question 3

Refer to the exhibit. After extending the logical volume, why does the df output still show 5.0G?

Accepted Answer

The filesystem needs to be resized with xfs_growfs.. The output shows the logical volume was extended (e.g., from 5G to 10G), but the filesystem itself has not been resized to use the new space. For XFS filesystems, the `xfs_growfs` command must be run to expand the filesystem to match the logical volume size. The `df` command reports filesystem usage, not block device size, so it still shows 5.0G until the filesystem is grown.

Answer

The lvextend command failed silently.

Answer

The filesystem type is ext4 and requires resize2fs.

Answer

The mount point /data is not accessible.

Question 4

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 5

The /data filesystem is at 99% capacity. The LVM setup shows that the volume group has 50GB free space, but the logical volume is only 100GB. What is the correct sequence of commands to increase the filesystem to use all available space in the volume group?

Accepted Answer

lvextend -L +50G /dev/mapper/vg01-data && xfs_growfs /data. The volume group has 50GB free space, so you need to extend the logical volume by +50GB (not to 50GB) using `lvextend -L +50G`, and then grow the XFS filesystem with `xfs_growfs /data` (the mount point, not the block device). The `+` sign indicates an addition to the current size, while omitting it would set an absolute size.

Answer

lvextend -L 50G /dev/mapper/vg01-data && xfs_growfs /dev/mapper/vg01-data

Answer

lvextend -L +50G /dev/mapper/vg01-data && resize2fs /dev/mapper/vg01-data

Answer

xfs_growfs /dev/mapper/vg01-data && lvextend -L +50G /dev/mapper/vg01-data

Question 6

A production server running Red Hat Enterprise Linux 9 hosts multiple Podman containers. The system administrator wants to ensure that a critical container named 'payments' automatically starts when the host boots, even if no user is logged in. The administrator has already created a systemd service file at /etc/systemd/system/container-payments.service. The service file contains: [Unit] Description=Payments container [Service] ExecStart=/usr/bin/podman start -a payments ExecStop=/usr/bin/podman stop payments Type=forking Restart=always [Install] WantedBy=multi-user.target. After enabling the service with 'systemctl enable container-payments.service' and rebooting, the container does not start. The administrator checks 'systemctl status container-payments.service' and sees that the service is inactive (dead). What is the most likely reason and the correct fix?

Accepted Answer

Remove the manual unit and instead use 'podman generate systemd --new --name payments payments:latest' to create a proper systemd unit that includes container creation, then enable the generated service. The existing systemd unit file uses `ExecStart=/usr/bin/podman start -a payments`, which assumes the container already exists. On a fresh boot, Podman containers are not automatically recreated unless the systemd unit includes container creation. Using `podman generate systemd --new` produces a unit that includes `ExecStartPre` directives to create the container from the image before starting it, ensuring the container exists and starts on boot.

Answer

Configure podman auto-update to automatically start the container on boot

Answer

Add --restart=always to the ExecStart line in the existing unit file

Answer

Set RestartSec=0 in the [Service] section to eliminate any delay

Question 7

Which TWO commands show detailed information about a container image, including layers and configuration? (Choose TWO.)

Accepted Answer

podman image tree . `podman image tree ` displays the image's layer hierarchy, showing parent-child relationships and layer sizes. Option E is correct because `podman inspect ` returns detailed metadata in JSON format, including the image's configuration (e.g., environment variables, entrypoint) and layer digests. Both commands provide the detailed information about layers and configuration that the question asks for.

Answer

podman ps -a

Answer

podman images <image>

Answer

podman history <image>

Question 8

A company requires that SSH access from the external network (10.0.1.0/24) only be allowed to port 2222, and all other incoming traffic on the firewall should be dropped. Which firewalld rule should be applied to the external zone?

Accepted Answer

firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" port port="2222" protocol="tcp" accept' --permanent. It uses a rich rule to explicitly allow incoming TCP traffic on port 2222 from the 10.0.1.0/24 source network, which matches the requirement. The default target for the external zone is 'drop', so only explicitly permitted traffic is allowed; this rule ensures SSH on port 2222 is accepted while all other incoming traffic is dropped.

Answer

firewall-cmd --zone=external --add-service=ssh --permanent

Answer

firewall-cmd --zone=external --add-port=2222/tcp --permanent

Answer

firewall-cmd --zone=external --add-rich-rule='rule family="ipv4" source address="10.0.1.0/24" service name="ssh" accept' --permanent

Question 9

A user executes the script shown in the exhibit with './export_script.sh' and then runs 'echo $MY_VAR' in the same terminal. The output is empty. Why does this happen?

Accepted Answer

The script runs in a sub-shell, so exported variables are not available to the parent shell. When a script is executed with './export_script.sh', it runs in a sub-shell (a child process). The 'export' command within the script makes the variable available to that sub-shell and its own child processes, but not to the parent shell that invoked the script. Therefore, after the script exits, the variable MY_VAR is not defined in the parent shell's environment, resulting in an empty output from 'echo $MY_VAR'.

Answer

The script lacks execute permissions

Answer

The 'export' command is incorrectly placed after the variable assignment

Answer

The variable name should be in uppercase for it to be inherited

Question 10

Refer to the exhibit. The script produces the error shown. What is the most likely cause?

Accepted Answer

The variable $var is empty or unset.. The error 'unary operator expected' occurs in bash when the `[ ]` test command encounters an empty or unset variable on the left side of a comparison operator. Since `$var` is empty, the expression `[ $var = 'value' ]` expands to `[ = 'value' ]`, which is syntactically invalid because the `=` operator expects a left operand. Option D correctly identifies this as the root cause.

Answer

The = operator should be == for string comparison.

Answer

The string 'value' contains spaces.

Answer

The script is missing a valid shebang.

Question 11

A developer needs to compile software from source and install it under /opt/custom. To avoid affecting the system package manager, which approach should be used?

Accepted Answer

Compile with './configure --prefix=/opt/custom' and then 'make install'. Using `./configure --prefix=/opt/custom` sets the installation root to `/opt/custom`, which keeps the compiled software completely separate from the system-managed directories (e.g., `/usr`, `/usr/local`). Running `make install` then installs all files under this custom prefix, ensuring the system package manager (RPM/YUM/DNF) is not affected by the manual installation.

Answer

Compile and install with default paths, then use 'make uninstall' to remove

Answer

Compile with './configure --prefix=/opt/custom' and use 'checkinstall' to create an RPM

Answer

Compile with './configure --prefix=/usr' and then install

Question 12

Which THREE options are valid when creating a new partition with the 'parted' command? (Choose three.)

Accepted Answer

Setting the partition's bootable flag. The 'parted' command can set the bootable flag on a partition using the 'set' command (e.g., 'set 1 boot on'). This flag is used by legacy BIOS bootloaders to identify the active partition, and it is a standard operation in MBR and GPT partition tables.

Answer

Setting the partition's UUID

Answer

Mounting the partition to a directory

Question 13

Which of the following is the correct way to persistently mount a filesystem using its UUID?

Accepted Answer

UUID=1234 /mnt xfs defaults 0 0. The /etc/fstab entry uses the 'UUID=' prefix followed by the actual UUID value to persistently mount a filesystem. The kernel reads this line at boot time and resolves the UUID to the corresponding block device, ensuring the mount is consistent regardless of device name changes.

Answer

LABEL=1234 /mnt xfs defaults 0 0

Answer

/dev/disk/by-uuid/1234 /mnt xfs defaults 0 0

Answer

PARTUUID=1234 /mnt xfs defaults 0 0

Question 14

A company policy requires that all cron jobs run by non-root users must be logged to a specific file /var/log/usercron.log. The system administrator decides to use rsyslog to capture these messages. Which configuration directive should be added to /etc/rsyslog.conf or a file in /etc/rsyslog.d/ to achieve this?

Accepted Answer

cron.* /var/log/usercron.log. The cron facility in rsyslog captures messages generated by the cron daemon, including cron jobs run by non-root users. By adding the directive `cron.* /var/log/usercron.log` to the rsyslog configuration, all cron messages (regardless of priority) are logged to the specified file, satisfying the policy requirement.

Answer

user.* /var/log/usercron.log

Answer

*.* /var/log/usercron.log

Answer

authpriv.* /var/log/usercron.log

Question 15

Which THREE commands can be used to monitor real-time process status and update the display every 2 seconds? (Choose three.)

Accepted Answer

htop. A is correct because `htop` is an interactive process viewer that by default updates in real-time (every ~1-2 seconds) and allows you to monitor processes dynamically. It provides a color-coded, user-friendly interface with CPU, memory, and swap usage bars, updating continuously without needing a separate interval flag.

Answer

ps aux

Answer

at 2

Question 16

A Red Hat Enterprise Linux 9 system has a logical volume 'lv_data' in the volume group 'vg_data' that needs to be resized from 10G to 15G. The underlying physical volumes have enough free space. Which sequence of commands correctly resizes the logical volume and the ext4 filesystem?

Accepted Answer

lvextend -L 15G /dev/vg_data/lv_data; resize2fs /dev/vg_data/lv_data. To resize an ext4 filesystem on a logical volume, you must first extend the logical volume with `lvextend -L 15G /dev/vg_data/lv_data` to allocate the additional 5G from the volume group, then use `resize2fs /dev/vg_data/lv_data` to grow the filesystem to fill the enlarged block device. This order ensures the underlying block device has sufficient capacity before the filesystem resize operation.

Answer

resize2fs /dev/vg_data/lv_data; lvextend -L 15G /dev/vg_data/lv_data

Answer

lvextend -L 15G /dev/vg_data/lv_data; xfs_growfs /dev/vg_data/lv_data

Answer

lvreduce -L 15G /dev/vg_data/lv_data; resize2fs /dev/vg_data/lv_data

Question 17

Refer to the exhibit. A web server runs as user 'apache'. The directory /var/www/html is owned by root:root with permissions 755. The administrator wants to allow the user 'webuser' to upload files to /var/www/html via SFTP. Which step is necessary to achieve this?

Accepted Answer

Change group ownership of /var/www/html to a group that includes webuser and add group write permission. Both options B and D are valid methods to grant write access to webuser without changing the ownership. Option B (changing group ownership and adding group write permission) works if a group including webuser is created and assigned. Option D (setting an ACL with setfacl -m u:webuser:w /var/www/html) provides the same result more flexibly, without modifying group permissions. Options A and C are incorrect because they do not directly address the permission issue.

Answer

Change webuser's shell to /bin/bash to allow SFTP login

Answer

Change the SELinux context of /var/www/html to httpd_sys_rw_content_t

Question 18

An administrator wants to enable user disk quotas on an XFS filesystem mounted at /home. Which steps are required?

Accepted Answer

Add 'uquota' to /etc/fstab, remount, then run xfs_quota -x -c 'limit -u bsoft=500m bhard=1g user1' /home. XFS uses its own quota management tools, not the traditional `quotacheck`/`edquota` tools used by ext4. The correct procedure is to add the `uquota` mount option to `/etc/fstab`, remount the filesystem, and then use `xfs_quota` to set limits. The `xfs_quota` command with the `-x` (expert) flag and `-c` (command) flag allows setting user quotas directly, and the path `/home` specifies the filesystem.

Answer

Add 'usrquota' to /etc/fstab, remount, then run quotacheck and edquota

Answer

Quotas are not supported on XFS filesystems

Answer

Use mount -o uquota /home, then setquota -u user1 500M 1G /home

Question 19

A system administrator notices that a RHEL 9 server's /var/log/messages is filling up the /var partition. The administrator wants to ensure log rotation runs daily and keeps 4 weeks of logs. Which configuration file should be modified?

Accepted Answer

/etc/logrotate.d/syslog. /etc/logrotate.d/syslog is the configuration file that controls log rotation for system log files such as /var/log/messages. By modifying this file, the administrator can set the rotation frequency to daily and specify the number of weeks (e.g., rotate 28 for 4 weeks) to retain logs, directly addressing the requirement.

Answer

/etc/systemd/journald.conf

Answer

/etc/rsyslog.conf

Answer

/etc/cron.daily/logrotate

Question 20

Which THREE of the following are common steps to configure a system to automatically mount an NFS share at boot?

Accepted Answer

Ensure nfs-utils is installed. B is correct because the NFS client functionality in Red Hat Enterprise Linux is provided by the nfs-utils package. Without this package installed, the system lacks the necessary tools (such as mount.nfs and rpcbind) to mount NFS shares, making it impossible to configure automatic mounting at boot.

Answer

Run 'mount -a' after boot

Answer

Configure /etc/exports