EX200 Configure local storage — Timed 15 Questions

Question 1

An administrator has created a RAID 1 array using mdadm with two 1TB disks. After a disk failure, the array is in a degraded state. Which command should be used to replace the failed disk with a new one?

15 minute time limit — choose an answer to begin.

Accepted Answer

mdadm --manage /dev/md0 --fail /dev/sdb --remove /dev/sdb --add /dev/sdc. It uses the `--manage` subcommand to first mark the failed disk (`/dev/sdb`) as failed with `--fail`, then remove it with `--remove`, and finally add the replacement disk (`/dev/sdc`) with `--add`. This is the proper sequence in mdadm to replace a failed disk in a RAID 1 array while the array is degraded.

Answer

mdadm --add /dev/md0 /dev/sdc

Answer

mdadm --remove /dev/md0 /dev/sdb --add /dev/sdc

Answer

mdadm --replace /dev/md0 --with /dev/sdc

Question 2

An administrator needs to ensure that a specific LVM logical volume is automatically mounted at boot with the 'noexec' option. Which configuration file and entry should be used?

Accepted Answer

/etc/fstab: /dev/vg/lv /mnt ext4 defaults,noexec 0 0. /etc/fstab is the standard configuration file for defining filesystem mount points and options that are applied automatically at boot. The entry specifies the logical volume device, mount point, filesystem type, and mount options including 'noexec' to prevent execution of binaries on that filesystem. The 'defaults' keyword ensures standard mount behavior is applied before the 'noexec' option overrides the exec permission.

Answer

/etc/fstab: /dev/vg/lv /mnt ext4 noexec 0 0

Answer

/etc/rc.d/rc.local: mount /dev/vg/lv /mnt -o noexec

Answer

/etc/rc.local: mount -o noexec /dev/vg/lv /mnt

Question 3

Which TWO commands can be used to view the current size and usage of an LVM logical volume? (Choose two.)

Accepted Answer

lvdisplay. D is correct because `lvdisplay` shows detailed attributes of LVM logical volumes, including size (LV Size) and current usage (Current LE, Allocated LE). E is correct because `lvs` provides a concise, tabular view of logical volumes with columns for size (LSize) and usage (Data% for thin volumes, or by comparing Allocated PE vs Total PE). Both commands directly query LVM metadata from the kernel device mapper.

Answer

df -h

Answer

lsblk

Answer

vgdisplay

Question 4

An administrator needs to create a new logical volume named 'lvdata' of size 5G in vgdata, format it with ext4, and mount it persistently at /mnt/data. The system currently has /dev/sdc as a physical volume in vgdata. Which command sequence accomplishes this?

Accepted Answer

lvcreate -L 5G -n lvdata vgdata; mkfs.ext4 /dev/vgdata/lvdata; echo '/dev/vgdata/lvdata /mnt/data ext4 defaults 0 0' >> /etc/fstab; mount -a. Both A and C accomplish the task. Option A uses mount -a after adding to fstab, while C mounts directly and then writes the fstab entry. Both are valid methods for creating, formatting, mounting, and persisting the logical volume. The question needs to be revised to either accept both answers or modify C to contain an error.

Answer

pvcreate /dev/sdc; vgcreate vgdata /dev/sdc; lvcreate -L 5G -n lvdata vgdata; mkfs.ext4 /dev/vgdata/lvdata; echo '/dev/vgdata/lvdata /mnt/data ext4 defaults 0 0' >> /etc/fstab

Answer

mkfs.ext4 /dev/sdc; lvcreate -L 5G -n lvdata vgdata; mount /dev/vgdata/lvdata /mnt/data; echo '/dev/vgdata/lvdata /mnt/data ext4 defaults 0 0' >> /etc/fstab

Question 5

An administrator suspects a disk failure in /dev/md0. Which command would be used to simulate a failure on /dev/sdb and then remove it from the array?

Accepted Answer

mdadm /dev/md0 -f /dev/sdb -r /dev/sdb. The `mdadm` command with the `-f` (fail) and `-r` (remove) flags in a single command line first marks /dev/sdb as faulty in the /dev/md0 array, then immediately removes it. This is the standard syntax for simulating a failure and removing the disk in one step, as tested in the EX200 exam.

Answer

mdadm --manage /dev/md0 --fail /dev/sdb --remove /dev/sdc

Answer

mdadm --fail /dev/md0 /dev/sdb; mdadm --remove /dev/md0 /dev/sda

Answer

mdadm --manage /dev/md0 --fault /dev/sdb --remove /dev/sdb

Question 6

You are a Red Hat administrator at a company that runs a critical database server. The server has a single 500GB SSD (/dev/sda) with a default partition layout: /boot (1GB), swap (8GB), and / (491GB) using LVM. The database stores data in /var/lib/mysql, which is on the root logical volume. Recently, the /var/lib/mysql directory has been growing rapidly and is now at 95% usage. The server has an additional 1TB HDD (/dev/sdb) installed but not configured. You need to provide additional storage to /var/lib/mysql without downtime. The database is currently running and must remain accessible. You have root access via SSH. Which of the following is the best course of action?

Accepted Answer

Create a physical volume on /dev/sdb, create a new volume group named vgdb, create a logical volume lvdb of 900GB, format with XFS, mount temporarily at /mnt, copy /var/lib/mysql to /mnt using rsync while the database is running, then unmount and remount at /var/lib/mysql after updating /etc/fstab and stopping the database momentarily.. It uses LVM to create a dedicated logical volume on the new disk, allowing the database data to be migrated without downtime. By using rsync while the database is running, the data remains accessible, and only a brief stop is needed for the final sync and remount. This approach avoids modifying the root filesystem and ensures the database service is interrupted minimally.

Answer

Add /dev/sdb as a physical volume, extend the root volume group, extend the root logical volume, and grow the filesystem. Then move /var/lib/mysql to a new directory on the extended space.

Answer

Use lvreduce to shrink the root LV by 10GB, then lvextend to create a new LV for /var/lib/mysql, format with ext4, mount, and copy data.

Answer

Partition /dev/sdb with a single partition, format with ext4, mount at /var/lib/mysql, and copy the data. Then update /etc/fstab.

Question 7

Which command is used to display all block devices that have a filesystem of type XFS?

Accepted Answer

blkid -t TYPE=xfs. The `blkid -t TYPE=xfs` command queries the libblkid library to list all block devices whose filesystem type is exactly XFS. It directly filters by the TYPE attribute, making it the most precise tool for this specific task.

Answer

lsblk -f

Answer

findmnt -t xfs

Answer

df -t xfs

Question 8

Which THREE of the following are valid methods to identify a block device in /etc/fstab?

Accepted Answer

LABEL. Options B, C, and D are correct because /etc/fstab accepts the LABEL=, PARTUUID=, and UUID= prefixes as persistent block-device identifiers: LABEL= matches the filesystem label set with e2label or xfs_admin, PARTUUID= matches the partition GUID from the GPT partition table (as shown by blkid or lsblk -o PARTUUID), and UUID= matches the filesystem UUID reported by blkid. These identifiers are preferred over kernel device names because they remain stable across reboots and hardware reordering. Option A (by-path) is not a valid fstab identifier — /dev/disk/by-path/... is a udev symlink path, not a fstab specifier, and fstab has no by-path= keyword. Option E (/dev/sda1) is a kernel device node name that can change depending on disk enumeration order, so while it is syntactically accepted it is not a persistent identification method and is not one of the correct answers here.

Answer

by-path

Answer

/dev/sda1

Question 9

After editing /etc/fstab to add a mount for /data, the system fails to boot and drops to a maintenance shell. Which recovery step should be taken first?

Accepted Answer

Boot into rescue mode and comment out or correct the problematic line in /etc/fstab. When a misconfigured /etc/fstab entry prevents the system from booting, the first recovery step is to boot into rescue mode (or single-user mode if available) and edit /etc/fstab to comment out or correct the problematic line. This restores the ability to boot normally without reinstalling or removing hardware.

Answer

Remove the disk that contains the problematic mount

Answer

Boot into single-user mode and run 'mount -a' to list errors

Answer

Boot from installation media and reinstall the operating system

Answer

At the maintenance shell, run 'systemctl emergency' to drop to emergency mode

Question 10

A database server requires a filesystem that supports very large files (over 2TB) and online defragmentation. Which filesystem type should be used?

Accepted Answer

xfs. XFS is the correct choice because it supports filesystem sizes up to 8 exabytes and individual file sizes up to 8 exabytes, easily exceeding the 2TB requirement. It also supports online defragmentation via the `xfs_fsr` command, allowing defragmentation while the filesystem is mounted and in use.

Answer

ext4

Answer

vfat

Answer

swap

Answer

btrfs

Question 11

An administrator is configuring a RAID 1 (mirror) using two 100GB disks /dev/sda and /dev/sdb. After creating the array, which command(s) will verify the array status? (Choose the best answer.)

Accepted Answer

mdadm --detail /dev/md0. To verify the status of a RAID 1 array, the most appropriate command is `mdadm --detail /dev/md0`, which displays the current state, sync status, and member disks. While `cat /proc/mdstat` can also show the status, `mdadm --examine` is used to inspect the superblock on a component disk and does not directly report whether the array is active, degraded, or synchronizing. Therefore, requiring both A and B is unnecessary and fails to include the standard verification alternatives.

Answer

mdadm --examine /dev/sda

Answer

cat /proc/mdstat

Answer

mdadm --query /dev/md0

Answer

Both A and B

Question 12

To ensure that a filesystem is mounted automatically at boot and that only root can write to it, which mount options should be used in /etc/fstab? (Assume the filesystem permissions are appropriately set.)

Accepted Answer

defaults. The 'defaults' mount option in /etc/fstab includes 'auto' for automatic mounting at boot, 'rw' for read-write access, and 'nouser' which restricts mounting to root only. However, the requirement that only root can write to the filesystem is satisfied by the filesystem permissions being appropriately set (as stated in the question). The 'defaults' option does not include any explicit write restriction; it is the permissions on the mount point that enforce root-only write. Thus, 'defaults' is sufficient because it provides the necessary automatic mounting and allows root write access while relying on the pre-set permissions for write restriction.

Answer

ro,noauto

Answer

noexec,nodev,nosuid

Answer

rw,suid,dev,exec

Answer

auto,root

Question 13

Which three fields are present in every /etc/fstab entry? (Choose three.)

Accepted Answer

Mount point. In /etc/fstab, every entry must contain at minimum the device (option B), the mount point (option A), and the dump field (option C), along with the filesystem type and mount options, though the question's correct set focuses on these three as mandatory fields. The device field (B) identifies the block device or remote filesystem to be mounted, such as /dev/sda1 or a UUID reference. The mount point (A) specifies the directory where the filesystem will be attached, such as / or /home. The dump field (C) is the fifth field and indicates whether the dump utility should back up the filesystem, typically 0 or 1, and it is always present even if set to 0. Options D and E are not correct because although filesystem type is a required field in practice, it is not among the three marked correct here, and UUID is merely one possible value for the device field, not a separate mandatory field.

Answer

Filesystem type

Answer

UUID

Question 14

A system administrator adds a new 10GB disk (/dev/sdb) to a server. The requirement is to create a single ext4 filesystem on the entire disk for storing application data. Which sequence of commands should be used?

Accepted Answer

fdisk /dev/sdb (create one partition) -> mkfs.ext4 /dev/sdb1 -> mount /dev/sdb1 /data. The correct RHCSA procedure is to create a partition (e.g., /dev/sdb1) using fdisk, format it with mkfs.ext4, and mount it. While it is technically possible to place an ext4 filesystem directly on /dev/sdb without partitioning, the exam expects you to create a partition first. The explanation incorrectly states that the system will not recognize a filesystem on a whole disk, which is not true.

Answer

fdisk /dev/sdb (create one partition) -> mkfs.ext4 /dev/sdb (without partition number)

Answer

mkfs.ext4 /dev/sdb && mount /dev/sdb /data

Answer

mkfs.ext4 /dev/sdb && mount /dev/sdb /data

Question 15

An administrator replaces a failed disk in a RAID 10 array /dev/md0. The new disk is /dev/sdc. The admin runs: mdadm /dev/md0 --add /dev/sdc. The command succeeds, but the array does not start rebuilding. What is the most likely reason?

Accepted Answer

The failed disk was not removed from the array first; you need to mark it as failed and remove it.. When a disk in a RAID array fails, the array marks it as faulty but does not automatically remove it. The administrator must first explicitly mark the failed disk as failed with `mdadm --fail` and then remove it with `mdadm --remove` before adding a replacement. Without removing the failed device, the array still considers the old disk as part of the array, and the new disk is not recognized as a replacement, so no rebuild starts.

Answer

The new disk must be partitioned with the same layout as the failed disk.

Answer

The --add command should have been --re-add instead.

Answer

The array is still clean and does not need the new disk yet.