EX200 Practice Exam 3 — 20 Questions

Question 1

The root filesystem is at 90% capacity. Which command increases available space without unmounting?

Accepted Answer

lvextend -L +5G /dev/mapper/vg_root-lv_root && xfs_growfs /. It first extends the logical volume with `lvextend -L +5G`, then grows the XFS filesystem online with `xfs_growfs /` to utilize the new space without unmounting. This is the proper procedure for XFS filesystems, which require `xfs_growfs` (not `resize2fs`) to expand while mounted.

Answer

fstrim /

Answer

resize2fs /dev/mapper/vg_root-lv_root

Answer

lvextend -L +5G /dev/mapper/vg_root-lv_root

Question 2

An administrator receives an alert that a process named 'apache2' is consuming excessive CPU. The administrator needs to identify the PID of the process and then change its priority to the lowest possible value (least favorable scheduling). Which sequence of commands should be used?

Accepted Answer

pidof apache2; renice -n 19 -p . `pidof apache2` retrieves the PID of the apache2 process, and `renice -n 19 -p ` sets the priority to the lowest possible (least favorable) scheduling value. In Linux, `renice` accepts nice values from -20 (highest priority) to 19 (lowest priority), so 19 is the correct value for the least favorable scheduling.

Answer

pidof apache2; renice -n 20 -p <PID>

Answer

ps -C apache2 -o pid=; renice -n -20 -p <PID>

Answer

ps aux | grep apache2; nice -n 19 <PID>

Question 3

A production server runs RHEL 8 with a software RAID 5 array (/dev/md0) composed of three disks: /dev/sda, /dev/sdb, /dev/sdc. The array is used to store database files. The server experiences a disk failure on /dev/sdc. The admin replaces /dev/sdc with an identical disk and wants to rebuild the array. He runs: mdadm /dev/md0 --add /dev/sdc. The command completes without error, but the array shows a degraded state after several hours. What should the admin do next?

Accepted Answer

Run mdadm --detail /dev/md0 to check the status and rebuild progress.. After adding a replacement disk to a RAID 5 array, the rebuild process begins automatically but may take hours depending on disk size and I/O load. Running `mdadm --detail /dev/md0` allows the admin to check the current state, rebuild progress (e.g., percentage complete), and any errors that might have stalled the rebuild. This is the first diagnostic step to determine if the rebuild is still ongoing, has failed, or is degraded for another reason.

Answer

Rebuild will happen automatically; just wait longer.

Answer

Recreate the array using mdadm --create with the same parameters.

Answer

Format /dev/sdc with a filesystem before adding to the array.

Question 4

A junior admin receives a ticket: 'The /var partition is filling up quickly. The server has an extra 100GB disk /dev/sdb. The /var filesystem is on logical volume lv_var in volume group vg_system. Currently, vg_system has no free extents. The admin's plan: create a new physical volume on /dev/sdb, extend vg_system, extend lv_var, and resize the filesystem. He runs: pvcreate /dev/sdb; vgextend vg_system /dev/sdb; lvextend -L+100G /dev/vg_system/lv_var; resize2fs /dev/vg_system/lv_var. The system reports error: 'resize2fs: Invalid argument while trying to open /dev/vg_system/lv_var'. What is the most likely mistake?

Accepted Answer

He used resize2fs instead of xfs_growfs because /var is typically XFS.. The error 'resize2fs: Invalid argument while trying to open /dev/vg_system/lv_var' indicates that the filesystem on lv_var is not ext2/3/4 but likely XFS. RHEL 8/9 defaults to XFS for /var, and XFS requires xfs_growfs (which operates on a mount point, not a block device) instead of resize2fs. Using resize2fs on an XFS filesystem produces this exact error.

Answer

He should have used lvresize instead of lvextend.

Answer

He forgot to run partprobe after pvcreate.

Answer

The lvextend command failed because vg_system has no free extents.

Question 5

A system has a new disk /dev/sdb that needs to be used as an LVM physical volume for an existing volume group 'vg_data'. Which sequence of commands is correct?

Accepted Answer

pvcreate /dev/sdb; vgextend vg_data /dev/sdb. The disk /dev/sdb must first be initialized as a physical volume using pvcreate, then added to the existing volume group vg_data using vgextend. This sequence properly extends the volume group with the new physical volume, as required by LVM.

Answer

vgcreate vg_data /dev/sdb; pvcreate /dev/sdb

Answer

lvextend vg_data /dev/sdb

Answer

pvcreate /dev/sdb; vgcreate vg_data /dev/sdb

Question 6

Which TWO LVM commands can be used to reduce the size of a logical volume?

Accepted Answer

lvresize. Both `lvresize` and `lvreduce` can reduce the size of a logical volume. `lvresize` is the general-purpose command for resizing LVs, and when used with the `-L` or `--size` option to specify a smaller size, it shrinks the volume. `lvreduce` is a dedicated command that specifically reduces the size of a logical volume, offering the same functionality as `lvresize --size` but with a more explicit name. Both commands require the filesystem to be shrunk first (if it contains data) using tools like `resize2fs` or `xfs_growfs` (though XFS cannot be shrunk).

Answer

lvchange

Answer

lvdisplay

Answer

lvextend

Question 7

After restoring files from backup, an SELinux context of a directory is not correct. Which command will restore the file contexts to the system defaults?

Accepted Answer

restorecon -R /directory. The `restorecon -R /directory` command reads the default SELinux contexts from the policy (stored in the file_contexts database) and applies them recursively to the specified directory. This is the standard method to reset file contexts to system defaults after a restore or misconfiguration.

Answer

chcon -R default_t /directory

Answer

semanage fcontext -R /directory

Answer

setfiles -v /directory

Question 8

An administrator has a logical volume 'lv_data' in a volume group 'vg_data' with a filesystem. The administrator needs to reduce the size of 'lv_data' by 2GB. Which sequence of commands should be performed?

Accepted Answer

umount, e2fsck -f, resize2fs, lvreduce. Reducing a logical volume with a filesystem requires a specific sequence: first unmount the filesystem to ensure no writes occur, then run e2fsck -f to force a filesystem check and ensure consistency, then use resize2fs to shrink the filesystem to the desired size, and finally lvreduce to shrink the logical volume itself. This order prevents data corruption by resizing the filesystem before the underlying block device.

Answer

lvreduce, resize2fs, e2fsck, umount

Answer

resize2fs, lvreduce, umount, e2fsck

Answer

umount, lvreduce, resize2fs, e2fsck

Question 9

A user wants to display the contents of a file in reverse line order. Which command should be used?

Accepted Answer

tac file. The `tac` command is the standard Linux utility for displaying a file in reverse line order. It reads the file from the last line to the first, effectively reversing the line sequence. This is the correct tool for the task described.

Answer

tail -r file

Answer

sort -r file

Answer

rev file

Question 10

A filesystem reports 0% free space in df -h, but when checking the directory size with du -sh, it shows much less usage. What is the most likely cause?

Accepted Answer

Deleted files still held open by processes. When a file is deleted while a process still holds an open file descriptor to it, the file's data blocks remain allocated on disk and are not freed until the process closes the descriptor. The `df` command reports disk usage based on the filesystem's block allocation, which still counts those blocks as used, while `du` calculates usage by walking the directory tree and cannot see the deleted file's data, leading to the discrepancy.

Answer

Filesystem is corrupted

Answer

The disk has bad sectors

Answer

Filesystem is mounted with noexe

Question 11

A web server is running in enforcing mode with SELinux, but Apache cannot read content in a custom directory /web. The directory has been labeled correctly with httpd_sys_content_t. However, access is still denied. What is the most likely cause?

Accepted Answer

The directory has incorrect permissions of 700.. Even though the SELinux context is correctly set to httpd_sys_content_t, the directory has permissions of 700 (rwx------). This means only the owner (typically root) can read, write, or execute the directory. The Apache httpd process runs as the 'apache' or 'httpd' user, which is not the owner, so it is denied read access. SELinux enforces its own policy, but DAC (Discretionary Access Control) permissions are checked first; if DAC denies access, SELinux never gets to evaluate the context match.

Answer

SELinux boolean httpd_enable_homedirs is off.

Answer

The httpd process is running in permissive mode.

Answer

The files are labeled with default_t.

Question 12

Refer to the exhibit. A web server must also accept HTTPS traffic on port 8443. Which command should the administrator run to permanently open this port?

Accepted Answer

firewall-cmd --add-port=8443/tcp --permanent && firewall-cmd --reload. It uses `--add-port=8443/tcp` to open a non-standard port (8443) for HTTPS traffic, applies the `--permanent` flag to persist the rule across reboots, and then runs `--reload` to activate the change immediately without restarting the firewall service. Without `--reload`, the permanent rule would not take effect until the next firewall reload or system restart.

Answer

firewall-cmd --add-service=8443/tcp --permanent

Answer

firewall-cmd --add-port=8443/tcp

Answer

firewall-cmd --add-port=8443/tcp --zone=public

Question 13

A user complains that the 'ls' command no longer outputs colors. The administrator suspects a change in environment variables. Which command would help diagnose the issue?

Accepted Answer

env. The `env` command displays all current environment variables, which directly affect the behavior of commands like `ls`. The `ls` command uses the `LS_COLORS` environment variable to determine color output; if this variable is missing or altered, colors will not appear. Running `env` allows the administrator to inspect the current environment and identify if `LS_COLORS` has been changed or unset.

Answer

set

Answer

declare

Answer

alias

Question 14

A system administrator needs to allow members of the 'developers' group to run any command as root without being prompted for a password. Which sudoers configuration line should be added?

Accepted Answer

%developers ALL=(ALL) NOPASSWD: ALL. The line `%developers ALL=(ALL) NOPASSWD: ALL` grants all members of the 'developers' group (indicated by the `%` prefix) permission to run any command as any user (including root) via sudo without being prompted for a password. The `NOPASSWD` tag is the key directive that bypasses password authentication, which directly matches the requirement to run commands as root without a password.

Answer

%developers ALL=(root) PASSWD: ALL

Answer

developers ALL=(ALL) NOPASSWD: ALL

Answer

%developers ALL=(ALL) ALL

Question 15

What is the default filesystem type in Red Hat Enterprise Linux 8?

Accepted Answer

XFS. In Red Hat Enterprise Linux 8, the default filesystem type is XFS. XFS is a high-performance 64-bit journaling filesystem that supports large files and filesystems, and it has been the default since RHEL 7. The Anaconda installer selects XFS by default for the root filesystem during a standard installation.

Answer

btrfs

Answer

ZFS

Answer

ext4

Question 16

Which command displays the current system time, timezone, and whether NTP synchronization is active?

Accepted Answer

timedatectl. The `timedatectl` command (option C) is the correct tool in Red Hat Enterprise Linux (RHEL) for querying and configuring system time, timezone, and NTP synchronization status. It displays the current local time, timezone, and whether NTP is active or enabled in a single, clear output, making it the standard utility for these tasks in systemd-based systems.

Answer

ntpq -p

Answer

date

Answer

cal

Question 17

An administrator has an XFS filesystem on a logical volume /dev/vg_data/lv_data mounted at /data. To extend the filesystem by 10GB, which sequence of commands is correct?

Accepted Answer

lvextend -L +10G /dev/vg_data/lv_data; xfs_growfs /data. For XFS filesystems, the logical volume must be extended first with `lvextend`, then the filesystem must be grown online using `xfs_growfs` with the mount point as the argument. XFS does not support shrinking and requires this specific order; `resize2fs` is only for ext2/3/4 filesystems.

Answer

lvextend -L +10G /dev/vg_data/lv_data; resize2fs /dev/vg_data/lv_data

Answer

xfs_growfs /data; lvextend -L +10G /dev/vg_data/lv_data

Answer

resize2fs /dev/vg_data/lv_data; lvextend -L +10G /dev/vg_data/lv_data

Question 18

Which THREE of the following are valid and recommended practices when writing shell scripts for RHEL?

Accepted Answer

Using 'local' keyword for variable declarations inside functions.. The 'local' keyword restricts a variable's scope to the function where it is declared, preventing unintended side effects on global variables. This is a recommended practice in RHEL shell scripting to maintain modularity and avoid namespace pollution.

Answer

Using 'set -e' to exit on non-zero exit codes.

Answer

Using the 'source' command instead of '.' for readability.

Question 19

During boot, a custom application fails because the /data file system is not mounted. Upon investigation, the administrator sees an error 'UUID=abc123 not found' in the logs. Which command should the administrator use to correct the /etc/fstab entry?

Accepted Answer

blkid /dev/sdb1. The error 'UUID=abc123 not found' indicates that the /etc/fstab entry for /data references a UUID that does not match any block device. The administrator needs to find the correct UUID of the actual partition (e.g., /dev/sdb1) and update the fstab entry. The `blkid /dev/sdb1` command displays the UUID (and filesystem type) of that specific device, allowing the administrator to copy the correct UUID into /etc/fstab.

Answer

mount -a

Answer

xfs_info /dev/sdb1

Answer

fdisk -l /dev/sdb1

Answer

lsblk -f /dev/sdb1

Question 20

A Red Hat Enterprise Linux system has a second disk /dev/sdb with a single partition /dev/sdb1 that was formatted as XFS and mounted at /mnt/backup. The administrator wants to change the filesystem on /dev/sdb1 to ext4 without losing existing data. Which steps should be taken in order?

Accepted Answer

Backup data, unmount, mkfs.ext4, remount, restore data. You cannot convert an XFS filesystem to ext4 in place; the only safe method is to back up the data, unmount the partition, create a new ext4 filesystem with mkfs.ext4, remount, and then restore the data. XFS and ext4 have fundamentally different on-disk structures (e.g., allocation groups vs. block groups, different journaling formats), so no in-place conversion tool exists.

Answer

Unmount, mkfs.ext4 /dev/sdb1, then mount

Answer

Use xfs_admin to change type

Answer

Use fsck.ext4 to convert in place