LFCS Storage Management — Timed 20 Questions

Question 1

Which TWO commands can be used to create a new physical volume for use with LVM? (Choose two.)

Accepted Answer

pvcreate /dev/sdb1. To create a physical volume for LVM, the correct command is `pvcreate /dev/sdb1`, which initializes the device as a PV by writing LVM metadata. Option D (`fdisk /dev/sdb` with type 8e) only creates a partition and sets its type to Linux LVM; it does not initialize the partition as a PV. A subsequent `pvcreate` is required to actually create the PV.

Answer

mkfs.ext4 /dev/sdb1

Answer

pvresize /dev/sdb1

Answer

fdisk /dev/sdb (then set type to 8e)

Answer

pvdisplay /dev/sdb1

Question 2

A system administrator is tasked with setting up a new 2TB disk for a database server. The database requires high read/write performance and redundancy. The server has a hardware RAID controller, but the administrator wants to use Linux software RAID for flexibility. Which of the following RAID levels should the administrator choose to maximize performance while providing fault tolerance, assuming the disk will be part of a larger array in the future?

Accepted Answer

RAID 10. RAID 10 (striping of mirrors) provides both high read/write performance and fault tolerance by combining the speed of RAID 0 striping with the redundancy of RAID 1 mirroring. Since the administrator plans to add more disks to the array in the future, RAID 10 scales well with additional pairs, maintaining performance and redundancy without the parity calculation overhead of RAID 5 or RAID 6.

Answer

RAID 5

Answer

RAID 0

Answer

RAID 6

Question 3

An administrator wants to extend a logical volume named 'lv_data' in volume group 'vg_data' by 5GB. The volume group has free physical extents. Which command should be used?

Accepted Answer

lvextend -L +5G /dev/vg_data/lv_data. The correct command to extend a logical volume is `lvextend`. Option B uses the correct syntax with the `-L +5G` flag, which adds 5GB to the existing logical volume `/dev/vg_data/lv_data`. The volume group `vg_data` has free physical extents, so the extension can proceed without needing to add new physical volumes.

Answer

pvextend -L +5G /dev/vg_data/lv_data

Answer

lvresize -L +5G /dev/vg_data/lv_data

Answer

lvextend -L 5G /dev/vg_data/lv_data

Question 4

A storage administrator notices that a newly created XFS filesystem on a logical volume shows only 90% of the expected capacity. The logical volume is 100GB. What is the most likely cause?

Accepted Answer

The filesystem was created with a reduced size due to mkfs.xfs default settings.. B is correct because `mkfs.xfs` by default reserves 10% of the filesystem space for metadata and performance optimization (the `-i maxpct` and internal log overhead). This is not a capacity loss but a design feature of XFS, which explains why a 100GB logical volume shows only ~90GB usable.

Answer

The disk has bad blocks that were marked as unusable.

Answer

The volume group has insufficient physical extents.

Answer

The filesystem is mounted with the 'noatime' option.

Question 5

Which command can be used to display the UUID of a filesystem on /dev/sdb1?

Accepted Answer

blkid /dev/sdb1. The blkid command is specifically designed to locate and print block device attributes, including the UUID and filesystem type. When run against a device like /dev/sdb1, it queries the kernel's device mapper and reads the filesystem superblock to extract the universally unique identifier (UUID). This is the most direct and reliable method for displaying a filesystem's UUID.

Answer

tune2fs -l /dev/sdb1

Answer

df -h /dev/sdb1

Answer

lsblk /dev/sdb1

Question 6

An administrator needs to mount an XFS filesystem with options to optimize for a database workload. Which mount option would reduce metadata updates to improve performance?

Accepted Answer

noatime. The `noatime` mount option disables updates to the inode access time (atime) on every file read. For database workloads, this eliminates a significant source of metadata write I/O, reducing disk contention and improving overall performance by avoiding unnecessary journal updates on XFS.

Answer

noexec

Answer

nodiratime

Answer

relatime

Question 7

Which THREE are valid reasons to use a swap file instead of a swap partition? (Choose three.)

Accepted Answer

Can be placed on a filesystem that supports sparse files.. Swap files can be placed on filesystems that support sparse files (e.g., ext4, XFS). A sparse file allocates disk blocks only when data is written, allowing a large swap file to be created without consuming the full physical disk space immediately. This is useful for systems where disk space is at a premium or where swap size needs to be overcommitted.

Answer

Required for hibernation (suspend-to-disk).

Answer

Faster performance than swap partition.

Question 8

You are a Linux administrator at a mid-sized company. The company runs a critical PostgreSQL database on a server running CentOS 7. The database stores its data on a 500GB logical volume (lv_pgdata) in volume group vg_pg. The filesystem is XFS. Recently, the database team reports that write performance is degrading, and the disk is nearly full (95% usage). You have added a new 200GB SSD to the server, and you need to increase the storage capacity and improve write performance for the database. The database can tolerate a brief downtime (less than 5 minutes) for maintenance. You want to use LVM to add the new SSD as a physical volume, extend the volume group, and then extend the logical volume and filesystem. Additionally, you want to improve write performance by placing the frequently written database transaction log on a separate faster storage. However, the database configuration expects the transaction log to be in a subdirectory of the data directory. You have the following options: A. Create a new logical volume for the transaction log, format it as XFS, mount it on the data directory's subdirectory, and move the log files. B. Add the SSD as a PV, extend vg_pg, extend lv_pgdata, and then use LVM's pvmove to move all extents to the SSD. C. Add the SSD as a PV, create a new VG, create a new LV for the transaction log, format as ext4, mount, and reconfigure the database. D. Use LVM's striping (RAID 0) across the existing HDD and new SSD to improve performance, then extend the filesystem. Which option best meets the requirements of increasing capacity and improving write performance with minimal downtime?

Accepted Answer

Add the SSD as a PV, extend vg_pg, extend lv_pgdata and resize the filesystem for capacity. Then create a new LV on the SSD, format as XFS, mount it on the transaction log subdirectory, move the log files, and update the database configuration to point to the new location.. It directly addresses both requirements: increasing capacity by extending the existing logical volume and filesystem using the new SSD as a PV, and improving write performance by isolating the database transaction log onto the faster SSD via a separate LV mounted on the expected subdirectory. This approach minimizes downtime (under 5 minutes) by performing the resize and mount operations quickly, and it respects the database's configuration expectation that the transaction log resides in a subdirectory of the data directory.

Answer

Add the SSD as a PV, extend vg_pg, extend lv_pgdata and resize the filesystem for capacity. Then use pvmove to move all data to the SSD, leaving the HDD unused.

Answer

Use LVM's striping (RAID 0) across the existing HDD and new SSD to improve performance, then extend the filesystem.

Answer

Add the SSD as a PV, create a new VG and LV for the transaction log, format as ext4, mount, and reconfigure the database to use the new location.

Question 9

A system administrator notices that a new 500GB SSD (/dev/sdb) is not being recognized by the system after installation. The server uses UEFI and GPT partitioning. Which command should the administrator run first to verify that the disk is detected by the kernel?

Accepted Answer

lsblk. The `lsblk` command lists all block devices recognized by the kernel, including those without a filesystem or partition table. Since the disk is new and not yet partitioned, `lsblk` will show it if the kernel has detected it, making it the correct first diagnostic step.

Answer

fdisk -l /dev/sdb

Answer

cat /proc/cpuinfo

Answer

lsusb

Question 10

A Linux administrator needs to create a RAID 5 array using three disks: /dev/sdb, /dev/sdc, and /dev/sdd, each 2TB. The administrator wants to ensure the array can be reassembled automatically after a reboot. Which command should be used to create the array?

Accepted Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2. It uses `--metadata=1.2`, which stores the superblock at a standard 4 KiB offset from the start of each device, enabling the kernel to automatically discover and assemble the RAID array on reboot without manual intervention. RAID 5 with three disks provides striping with distributed parity, offering a balance of performance and redundancy.

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=0.90

Answer

mdadm --create /dev/md0 --level=1 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd

Answer

mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd

Question 11

Which TWO commands can be used to mount a filesystem on /dev/sdb1 to /mnt/data?

Accepted Answer

mount /dev/sdb1 /mnt/data. The standard syntax for the mount command is `mount [options] `, so `mount /dev/sdb1 /mnt/data` correctly specifies the device first and the target directory second. Option C is also correct because it explicitly specifies the filesystem type with `-t ext4`, which is a valid and common practice when mounting a filesystem, ensuring the kernel uses the correct driver.

Answer

mount /mnt/data /dev/sdb1

Answer

mount -o loop /dev/sdb1 /mnt/data

Answer

mount -t auto /dev/sdb1 /mnt/data -o loop

Question 12

Which THREE of the following are valid Linux filesystem types that can be used for root partitions on a modern Linux system?

Accepted Answer

XFS. XFS is a high-performance 64-bit journaling filesystem created by Silicon Graphics, now widely supported in the Linux kernel. It is a valid choice for root partitions on modern Linux systems, especially for large file and high-concurrency workloads, and is the default filesystem in Red Hat Enterprise Linux 7 and later.

Answer

NTFS

Answer

FAT32

Question 13

After extending the logical volume, the df output still shows 100G. What is the most likely reason?

Accepted Answer

The filesystem on the logical volume has not been resized.. `lvextend` only increases the size of the logical volume at the block device level. The filesystem (e.g., ext4, XFS) still sees the original size until it is explicitly resized with a command like `resize2fs` (for ext4) or `xfs_growfs` (for XFS). The `df` command reports filesystem usage, not the underlying block device size, so the filesystem must be grown to match the LV.

Answer

lvresize must be used instead of lvextend.

Answer

The kernel has not detected the new size; reboot required.

Answer

The mount point must be remounted with the 'remount' option.

Question 14

A system administrator receives an alert that disk /dev/sda is predicted to fail soon. The server uses LVM, and /dev/sda is part of a volume group named vg_system. Which of the following is the best course of action to replace the failing disk without downtime?

Accepted Answer

Use pvmove to move physical extents to another disk, then remove the old disk.. Pvmove relocates physical extents from /dev/sda to another physical volume in the same volume group while the filesystem remains online and accessible. This allows the failing disk to be removed from vg_system without any downtime, preserving LVM metadata and data integrity.

Answer

Use dd to clone /dev/sda to a new disk and then replace.

Answer

Use ddrescue to copy data, then replace the disk.

Answer

Remove /dev/sda from the volume group and add a new disk.

Question 15

The administrator wants to create a new logical volume of 5GB for /var/log. Which of the following is the most appropriate first step?

Accepted Answer

Add a new disk (e.g., /dev/sdc) to the system, create a PV, and extend vg_root.. The volume group vg_root currently has no free space to create a new logical volume. Adding a new disk, creating a physical volume (PV) on it, and extending vg_root with vgextend provides the necessary free extents. Only then can lvcreate be used to create the 5GB lv_var_log logical volume for /var/log.

Answer

Use lvresize to shrink lv_root by 5G and then create lv_var_log

Answer

Mount a new filesystem directly on a new partition /dev/sdc1

Answer

Use lvcreate -L 5G vg_root -n lv_var_log

Question 16

Your company runs a critical database server that uses a 2TB XFS filesystem mounted at /data. The filesystem resides on an LVM logical volume (lv_data) within a volume group (vg_data) that spans four physical volumes (each 600GB SSD). You have been receiving low-space alerts: /data is at 95% capacity. After reviewing usage, you determine that the database will need an additional 500GB within the next month. The server has no additional physical disks available, but there is an unused 1TB SSD in inventory that you can install. However, the server is in production and cannot be rebooted. The system uses a 5.10 Linux kernel. Which of the following is the best approach to increase the available space for /data?

Accepted Answer

Install the new SSD, create a partition with fdisk, run pvcreate, vgextend vg_data, lvextend -L +500G /dev/vg_data/lv_data, and then run xfs_growfs /data.. It follows the proper procedure to add a new physical disk to an existing LVM volume group, extend the logical volume, and then grow the XFS filesystem online without unmounting or rebooting. The `xfs_growfs` command is specifically designed to expand an XFS filesystem while it is mounted, which is essential for a production database server that cannot be rebooted.

Answer

Create a RAID 0 array with the existing SSDs and the new SSD using mdadm, then format with XFS and mount at a different mount point, then move data.

Answer

Shrink other logical volumes in vg_data that are not important to free up space, then extend lv_data.

Answer

Backup /data to an external drive, delete the logical volume, volume group, and physical volumes, then recreate everything including the new SSD to have a single large filesystem, then restore data.

Question 17

A system administrator needs to create a new ext4 filesystem on /dev/sdb1 with a reserved block percentage of 2% instead of the default 5%. Which command should be used?

Accepted Answer

mkfs.ext4 -m 2 /dev/sdb1. The `-m` flag in `mkfs.ext4` sets the reserved block percentage for the superuser, and specifying `-m 2` overrides the default of 5% to reserve only 2% of the blocks on the new ext4 filesystem on /dev/sdb1.

Answer

mkfs.ext4 -R 2 /dev/sdb1

Answer

mkfs.ext4 -r 2 /dev/sdb1

Answer

tune2fs -m 2 /dev/sdb1

Question 18

Which THREE of the following are valid methods to mount an NFS filesystem on a client?

Accepted Answer

mount -o hard,intr server:/export /mnt. The `mount` command with `-o hard,intr` specifies NFS-specific mount options: `hard` ensures that NFS operations retry indefinitely until the server responds, and `intr` allows signals to interrupt a hung NFS operation. The command `mount -o hard,intr server:/export /mnt` uses the default NFS version (typically NFSv3) and is a valid method to mount an NFS filesystem on a client.

Answer

echo 'server:/export /mnt nfs defaults 0 0' >> /etc/fstab && mount -a

Answer

mount -t cifs server:/share /mnt

Question 19

Refer to the exhibit. The administrator wants to create a RAID 1 array using /dev/sdb1 and /dev/sdc1. Which command should be used?

Accepted Answer

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1. RAID 1 (mirroring) requires exactly two devices to provide redundancy by duplicating data across both disks. The `--level=1` parameter specifies RAID 1, and `--raid-devices=2` matches the two partitions /dev/sdb1 and /dev/sdc1.

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=2 /dev/sdb1 /dev/sdc1

Answer

mdadm --create /dev/md0 --level=10 --raid-devices=2 /dev/sdb1 /dev/sdc1

Answer

mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sdb1 /dev/sdc1

Question 20

Order the steps to configure a cron job that runs a script every day at 2 AM.

Accepted Answer

Step 1: Run 'crontab -e' to open the crontab editor.
Step 2: Add the line '0 2 * * * /path/to/script'.
Step 3: Save and exit the editor.
Step 4: Run 'crontab -l' to verify the job is scheduled.. The correct order to configure a cron job is: open the crontab file with 'crontab -e', add the cron expression with the correct time fields (minute, hour, day, month, weekday) and the script path, save the file, and then verify with 'crontab -l'. Common mistakes include adding the line before opening the editor, saving before adding, or verifying before editing.

Answer

Step 1: Add the line '0 2 * * * /path/to/script' directly to the crontab.
Step 2: Run 'crontab -e' to open the editor.
Step 3: Save and exit the editor.
Step 4: Run 'crontab -l' to verify.

Answer

Step 1: Run 'crontab -e' to open the editor.
Step 2: Save and exit the editor immediately.
Step 3: Add the line '0 2 * * * /path/to/script'.
Step 4: Run 'crontab -l' to verify.

Answer

Step 1: Run 'crontab -l' to verify existing jobs.
Step 2: Run 'crontab -e' to open the editor.
Step 3: Add the line '0 2 * * * /path/to/script'.
Step 4: Save and exit.