LPIC-2 Block Devices, Filesystems and Advanced Storage — 20 Questions

Question 1

Which command can be used to display all UUIDs of block devices that contain filesystems?

Accepted Answer

lsblk -f. Both `lsblk -f` and `blkid` can display UUIDs for block devices that contain filesystems. `lsblk -f` lists filesystem information (including UUIDs) in a tree format, while `blkid` directly queries block device metadata. Option A (lsblk -f) and Option C (blkid) are both correct. Option B is not a valid command but a phrase, and it incorrectly refers to itself. Option D (fdisk -l) does not show UUIDs.

Answer

both A and B

Answer

fdisk -l

Question 2

A system administrator notices that a new 1TB NVMe drive (/dev/nvme0n1) is not detected by the kernel. The hardware is confirmed working. Which troubleshooting step should be taken first to check if the drive is recognized by the system's PCI subsystem?

Accepted Answer

Run lspci to verify the NVMe controller is detected.. The NVMe drive is not detected by the kernel, but the hardware is confirmed working. The first step is to verify whether the PCI subsystem sees the NVMe controller, because NVMe devices are connected via the PCI Express bus. Running lspci lists all PCI devices, including the NVMe controller; if it does not appear, the issue is at the PCI or hardware level, not the block layer.

Answer

Run lsblk to list all block devices.

Answer

Check dmesg output for errors.

Answer

Run fdisk -l /dev/nvme0n1 to probe the drive.

Question 3

An administrator is designing a high-availability storage solution using DRBD. The requirement is to have two nodes with synchronous replication and automatic failover in case of primary node failure. Which configuration best achieves this?

Accepted Answer

DRBD in Primary/Primary mode managed by Pacemaker cluster stack.. DRBD in Primary/Primary mode, managed by the Pacemaker cluster stack, provides synchronous replication and automatic failover. Pacemaker monitors node health and can promote the secondary node to primary automatically upon primary failure, meeting the high-availability requirement without manual intervention.

Answer

Export the DRBD block device via NFS and use a load balancer.

Answer

Primary/Secondary DRBD resource with manual failover using drbdadm.

Answer

DRBD with Heartbeat to automatically promote the secondary on primary failure.

Question 4

A filesystem is reported as 'read-only' after an unexpected power failure. Which command should be used to attempt repair without data loss?

Accepted Answer

fsck -n /dev/sda1. After an unexpected power failure, the filesystem may have been marked as needing a clean replay of its journal, but it is not necessarily corrupted. Running `fsck -n` performs a read-only check of the filesystem without making any changes, allowing you to assess the extent of damage or confirm that the journal replay is all that is needed. This avoids the risk of `fsck` making incorrect automatic repairs that could cause data loss, which is critical when the root cause is an unclean shutdown rather than structural corruption.

Answer

mount -o remount,rw /dev/sda1

Answer

fsck -y /dev/sda1

Answer

e2fsck -p /dev/sda1

Question 5

Which TWO statements about LVM thin provisioning are correct?

Accepted Answer

The filesystem on a thin volume must support the 'discard' option to free unused space.. Thin volumes allocate data blocks on demand from a thin pool. To allow the underlying physical storage to reclaim unused blocks when files are deleted, the filesystem must support the 'discard' option (or use fstrim) so that it can notify the device mapper of freed space. Without discard, the thin pool never learns that blocks are no longer in use, preventing space reclamation.

Answer

Thin pools are created using the 'pvcreate' command.

Answer

Thin provisioning requires a dm-cache device to function.

Answer

Thin volumes automatically grow when they run out of space.

Question 6

A Linux administrator is managing a database server running on CentOS 7 that uses ext4 filesystems on LVM. The server has three physical volumes: /dev/sda (200GB), /dev/sdb (200GB), and /dev/sdc (200GB) all in volume group 'vg_db'. The logical volume 'lv_data' (400GB) is used for database files. Recently, the DBA reports that database writes are slower than expected. Iostat shows high average wait times (>100ms) on /dev/sdc but normal on /dev/sda and /dev/sdb. The LVM stripes data across all three PVs with a stripe size of 64KB. Which action should the administrator take to improve performance?

Accepted Answer

Replace /dev/sdc with a new disk and restore the mirror or restripe.. The high average wait time on /dev/sdc indicates that this specific physical volume is a performance bottleneck, likely due to hardware failure or degradation. Since the logical volume 'lv_data' stripes data across all three PVs, the overall write performance is limited by the slowest device in the stripe set. Replacing /dev/sdc with a new disk and restoring the stripe (e.g., using pvmove to relocate extents and then replacing the device) eliminates the bottleneck and restores balanced I/O across all PVs.

Answer

Convert lv_data to linear mapping on /dev/sda and /dev/sdb only.

Answer

Increase the stripe size to 256KB to reduce I/O overhead.

Answer

Remove /dev/sdc from the volume group and reduce the stripe count to 2.

Question 7

A system administrator needs to create a new 500 MB ext4 filesystem on /dev/sdb1 and mount it persistently at /data. Which set of commands accomplishes this task?

Accepted Answer

mkfs.ext4 /dev/sdb1 && echo '/dev/sdb1 /data ext4 defaults 0 2' >> /etc/fstab && mount -a. It first creates an ext4 filesystem on /dev/sdb1 using mkfs.ext4, then appends a mount entry to /etc/fstab with the correct filesystem type (ext4) and mount point (/data), and finally runs mount -a to mount all filesystems from fstab, including the new one. This sequence ensures the filesystem is created, persistently configured, and immediately mounted.

Answer

mkfs -t ext4 /dev/sdb1 && mount /dev/sdb1 /data

Answer

blkid /dev/sdb1 && echo 'UUID=... /data ext4 defaults 0 2' >> /etc/fstab && mount -a

Answer

mkfs.xfs /dev/sdb1 && echo '/dev/sdb1 /data xfs defaults 0 2' >> /etc/fstab && mount -a

Question 8

Which TWO statements about LVM thin provisioning are correct?

Accepted Answer

It allows creating logical volumes that can be larger than the available physical storage.. LVM thin provisioning allows creating logical volumes that appear larger than the available physical storage (overcommitment). This is achieved by allocating data blocks on demand from a thin pool, rather than reserving them at creation time. The thin pool itself must have sufficient physical storage to accommodate actual writes, but the logical volume size can exceed the pool's capacity.

Answer

Thin pools automatically extend when they reach 80% usage.

Answer

A thin pool cannot be extended once created.

Answer

It is only supported on SSDs.

Question 9

The administrator wants to create a RAID 1 array using /dev/sdb1 and /dev/sdc1, then create a filesystem and mount it at /mnt/raid1. Which command sequence should be used first?

Accepted Answer

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1. The first step in creating a RAID 1 array is to assemble the underlying block devices into a RAID device using mdadm. The command `mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1` initializes the RAID metadata and creates the array at /dev/md0. Only after the array is created can a filesystem be built on it and then mounted.

Answer

mkfs.ext4 /dev/md0

Answer

pvcreate /dev/sdb1 /dev/sdc1

Answer

fdisk /dev/sdb && fdisk /dev/sdc

Question 10

Order the steps to configure a Linux system as a DHCP client using dhclient.

Accepted Answer

Configure the interface for DHCP, then run dhclient, then check the IP address, then verify the default route, then test connectivity.. First configure the interface for DHCP, then run dhclient, check address, verify route, and test.

Answer

Run dhclient first, then configure the interface for DHCP, then check the IP address, then verify the default route, then test connectivity.

Answer

Check the IP address first, then configure the interface for DHCP, then run dhclient, then verify the default route, then test connectivity.

Answer

Configure the interface for DHCP, then check the IP address, then run dhclient, then verify the default route, then test connectivity.

Question 11

Arrange the steps to configure a Linux system as a PostgreSQL database server.

Accepted Answer

Install PostgreSQL, then initialize the database cluster, then start the PostgreSQL service, then create a user and database, then test the connection.. The correct order to configure a Linux system as a PostgreSQL database server is: install PostgreSQL, initialize the database cluster using initdb, start the PostgreSQL service, create a database user and database, and then test the connection. Each step depends on the previous one; for example, starting the service requires the cluster to exist, and creating users requires the service to be running.

Answer

Install PostgreSQL, then start the PostgreSQL service, then initialize the database cluster, then create a user and database, then test the connection.

Answer

Install PostgreSQL, then initialize the database cluster, then create a user and database, then start the PostgreSQL service, then test the connection.

Answer

Install PostgreSQL, then start the PostgreSQL service, then create a user and database, then initialize the database cluster, then test the connection.

Question 12

Match each LVM term to its definition.

Accepted Answer

Physical Volume (PV): A physical disk or partition that is initialized for use by LVM.. In LVM, Physical Volumes (PVs) are physical disks/partitions; Volume Groups (VGs) pool them; Logical Volumes (LVs) are created from VGs; Physical Extents (PEs) are the smallest allocation units on PVs. Common confusions involve swapping VG and LV definitions or confusing PE with LV.

Answer

Logical Volume (LV): The smallest allocatable unit of space on a Physical Volume.

Answer

Volume Group (VG): A virtual block device that can be used as a filesystem.

Question 13

Match each security tool to its function.

Accepted Answer

iptables: A firewall tool used to set up, maintain, and inspect the tables of IP packet filter rules.. Correct matches: iptables is a firewall, nmap is a network scanner, tcpdump is a packet analyzer. Common confusions include misattributing file integrity checking to iptables, IP banning to nmap, and port scanning to tcpdump.

Answer

iptables: A tool for monitoring file system integrity.

Answer

nmap: A tool for banning IPs after failed login attempts.

Answer

tcpdump: A tool for scanning open ports.

Question 14

A Linux administrator notices that a newly added disk /dev/sdc is not recognized by the system. Which command should be used to rescan the SCSI bus without rebooting?

Accepted Answer

echo '- - -' > /sys/class/scsi_host/host0/scan. Writing '- - -' to /sys/class/scsi_host/host0/scan triggers a SCSI bus rescan on the specified host adapter (host0) without requiring a reboot. The three dashes represent 'channel, target, LUN' wildcards, instructing the kernel to scan all SCSI IDs on that bus to detect newly added devices like /dev/sdc.

Answer

echo 'scan' > /proc/scsi/scsi

Answer

blockdev --rereadpt /dev/sdc

Answer

service scsi restart

Question 15

An administrator needs to create an ext4 filesystem on /dev/sdb1 with a block size of 4096 bytes and reserve 2% of blocks for root. Which command accomplishes this?

Accepted Answer

mkfs.ext4 -b 4096 -m 2 /dev/sdb1. Mkfs.ext4 uses the `-b` option to specify the block size in bytes (4096) and `-m` to set the reserved blocks percentage for root (2%). The `-b` flag is the standard short form for block size in the mke2fs family of tools, and `-m` accepts a percentage value directly.

Answer

mkfs.ext4 --block-size 4096 -m 2 /dev/sdb1

Answer

mkfs.ext4 -B 4096 -m 2 /dev/sdb1

Answer

mkfs.ext4 -b 4096 -M 2 /dev/sdb1

Question 16

After adding a new LUN to an existing SAN, the administrator runs multipath -ll but sees the new LUN as 'failed'. The multipathd service is running. What is the most likely cause?

Accepted Answer

The new LUN has not been presented to the host from the SAN. When a new LUN appears as 'failed' in `multipath -ll` output, the most common cause is that the LUN has not been properly presented to the host from the SAN. Even if the multipathd service is running, multipathd can only manage devices that the SCSI layer has already discovered. If the SAN administrator has not zoned or masked the LUN to the host, the host's SCSI subsystem never sees the device, so multipathd reports it as 'failed' because it cannot find the underlying paths.

Answer

The multipathd daemon needs to be restarted

Answer

The /etc/multipath.conf needs to be edited to include the new LUN

Answer

The scsi device needs to be manually created with mknod

Question 17

An administrator needs to extend an ext4 filesystem on logical volume 'home' by 5 GB. The volume group 'vg' has free extents. Which sequence of commands is correct?

Accepted Answer

lvresize -L +5G /dev/vg/home; e2fsck -f /dev/vg/home; resize2fs /dev/vg/home. The correct sequence is to first extend the logical volume by the required size using `lvresize -L +5G` (or `lvextend`), optionally check the filesystem with `e2fsck -f`, and then resize the filesystem with `resize2fs`. This ensures the filesystem can utilize the newly allocated space. Option A is incorrect because it extends by all free extents, not exactly 5 GB. Option B reverses the order, which fails because `resize2fs` cannot extend beyond the current block device. Option C uses `mount -o remount`, which does not resize the filesystem.

Answer

lvextend -l +100%FREE /dev/vg/home; resize2fs /dev/vg/home

Answer

resize2fs /dev/vg/home; lvextend -L +5G /dev/vg/home

Answer

lvextend -L +5G /dev/vg/home; mount -o remount /dev/vg/home

Question 18

A database server experiences performance degradation. Analysis shows high I/O wait on a LVM logical volume that uses striping across two physical volumes. What is the most effective way to improve performance?

Accepted Answer

Add a cache layer using lvmcache on a fast SSD. Adding a cache layer using lvmcache on a fast SSD is the most effective way to reduce high I/O wait because it places frequently accessed (hot) data on the faster SSD while keeping the bulk of data on the slower striped HDDs. This directly addresses the I/O bottleneck without requiring data migration or downtime, and it leverages the existing striped layout for sequential throughput while improving latency for random reads/writes.

Answer

Increase the stripe size and recreate the LV

Answer

Add an additional PV to the VG and extend the LV

Answer

Convert the LV to use linear mapping instead of striping

Question 19

A system's root filesystem on /dev/sda1 is offline. The administrator boots into rescue mode and needs to check the filesystem integrity. Which command should be used first?

Accepted Answer

e2fsck -p /dev/sda1. `e2fsck -p` runs an automatic, non-interactive filesystem check on the ext2/ext3/ext4 filesystem, which is the safest first step when the root filesystem is offline and the administrator is in rescue mode. The `-p` flag automatically repairs any problems that can be safely fixed without user intervention, minimizing risk of further damage. This command is specifically designed for ext-family filesystems and is the recommended initial integrity check before attempting any manual repairs.

Answer

dumpe2fs /dev/sda1

Answer

fsck.ext4 -f /dev/sda1

Answer

fsck -N /dev/sda1

Question 20

An administrator creates a new XFS filesystem on /dev/vg/data and needs to mount it at /data with noatime and a stripe unit of 1 MiB. Which /etc/fstab entry is correct?

Accepted Answer

/dev/vg/data /data xfs defaults,noatime,sunit=2048 0 0. The `sunit` mount option specifies the stripe unit in 512-byte blocks. A stripe unit of 1 MiB equals 2048 blocks (1 MiB = 1024 KiB = 2048 * 512 bytes). The `noatime` option disables access time updates. This entry correctly mounts the XFS filesystem at /data with the required parameters.

Answer

/dev/vg/data /data xfs defaults,noatime,swidth=2048 0 0

Answer

/dev/vg/data /data xfs defaults,noatime,allocsize=1m 0 0

Answer

/dev/vg/data /data xfs defaults,noatime,sunit=1024 0 0