LFCS Practice Test 35 — 15 Questions

Question 1

An administrator is troubleshooting a server that cannot mount an XFS filesystem on /dev/sdb1. The command mount /dev/sdb1 /data fails with 'wrong fs type, bad option, bad superblock'. Which three commands can help diagnose the issue? (Choose three.)

Accepted Answer

dmesg | tail. Option A is correct because `dmesg | tail` displays the kernel ring buffer messages, which often contain detailed error information from the XFS driver when a mount fails. This can reveal specific reasons such as a corrupt superblock, wrong filesystem type detection, or missing kernel support, helping to pinpoint the root cause.

Answer

fsck /dev/sdb1

Answer

blkid /dev/sdb1

Question 2

An administrator needs to check the UUID of a filesystem on /dev/sdb1. Which command should be used?

Accepted Answer

blkid /dev/sdb1. The `blkid` command is specifically designed to locate and display block device attributes, including the UUID and filesystem type. Running `blkid /dev/sdb1` queries the device's superblock and outputs its UUID, making it the correct tool for this task.

Answer

df -h /dev/sdb1

Answer

mount | grep sdb1

Answer

fdisk -l /dev/sdb1

Question 3

A disk in a RAID5 array fails. The array is assembled using mdadm. Which is the correct procedure to replace the failed disk with a new one?

Accepted Answer

Run 'mdadm --fail /dev/md0 /dev/sdb', then 'mdadm --remove /dev/md0 /dev/sdb', then physically replace, then 'mdadm --add /dev/md0 /dev/sdb'.. Option C is correct because it follows the proper mdadm procedure for replacing a failed disk in a RAID5 array. First, you must mark the disk as failed with 'mdadm --fail' to ensure the array stops using it, then remove it with 'mdadm --remove' to detach it from the array. After physically replacing the disk, you add the new disk with 'mdadm --add', which triggers a rebuild of the array from the remaining disks' parity data.

Answer

Physically replace the disk, then run 'mdadm --add /dev/md0 /dev/sdb'.

Answer

Run 'mdadm --replace /dev/md0 /dev/sdb' with the new disk path.

Answer

Hot-swap the disk and the array automatically recovers.

Question 4

An administrator needs to encrypt a block device (/dev/sdc) using LUKS. Which command creates an encrypted LUKS container on the device?

Accepted Answer

cryptsetup luksFormat /dev/sdc. Option B is correct because `cryptsetup luksFormat /dev/sdc` initializes the block device with a LUKS header, setting up an encrypted container that can later be opened with a passphrase or key file. This is the standard command for creating a new LUKS partition, as it writes the LUKS metadata and prepares the device for encryption.

Answer

cryptsetup luksOpen /dev/sdc encrypted_device

Answer

openssl enc -aes-256-cbc -in /dev/sdc -out /dev/sdc.enc

Answer

dm-crypt create encrypted /dev/sdc

Question 5

After adding a new disk and creating an ext4 filesystem on /dev/sdc1 with mke2fs, the administrator added an entry to /etc/fstab to mount it at /data. However, after reboot, the filesystem is not mounted. Which of the following is the most likely cause?

Accepted Answer

The fstab entry uses the device name /dev/sdc1 instead of UUID.. Option C is correct because when using device names like /dev/sdc1 in /etc/fstab, the kernel may assign a different device name (e.g., /dev/sdb1) after reboot due to asynchronous device discovery, causing the mount to fail. Using the filesystem's UUID (universally unique identifier) ensures persistent identification regardless of device name changes, which is a best practice for ext4 filesystems created with mke2fs.

Answer

The filesystem superblock was corrupted.

Answer

The filesystem was not formatted correctly.

Answer

The mount point /data does not exist.

Question 6

A system administrator is setting up a high-availability cluster using shared storage. Which filesystem is best suited for this environment where multiple nodes need simultaneous read-write access to the same filesystem?

Accepted Answer

GFS2. GFS2 (Global File System 2) is a shared-disk cluster filesystem designed for high-availability environments where multiple nodes require simultaneous read-write access to the same filesystem. It uses a distributed lock manager (DLM) to coordinate access across nodes, ensuring data consistency without requiring a single metadata server. This makes it ideal for active-active cluster configurations with shared block storage.

Answer

Btrfs

Answer

XFS

Answer

ext4

Question 7

Which command displays the UUID of all filesystems on the system?

Accepted Answer

lsblk -f. The `lsblk -f` command lists all block devices and includes the filesystem type and UUID for each filesystem, making it the correct choice for displaying UUIDs of all filesystems on the system. The `-f` option specifically adds filesystem information, including UUIDs, to the output.

Answer

blkid

Answer

df -h

Answer

fdisk -l

Question 8

An administrator receives a report that a specific directory /var/log is consuming too much disk space. Which command should be used to determine the total disk space used by that directory?

Accepted Answer

du -sh /var/log. Option D is correct because the `du -sh /var/log` command calculates the total disk space used by the specified directory. The `-s` flag summarizes the total size, `-h` provides human-readable output (e.g., in KB, MB, GB), and the path `/var/log` targets the directory in question. This is the standard Linux command for determining directory disk usage.

Answer

df -h /var/log

Answer

ls -la /var/log

Answer

fdisk /var/log

Question 9

An administrator created an LVM snapshot of a logical volume to perform a backup. During the backup, the snapshot runs out of space. What will happen to the original logical volume?

Accepted Answer

The snapshot becomes invalid and must be recreated.. When an LVM snapshot runs out of space, it becomes invalid and cannot track changes made to the original logical volume during the backup. The snapshot is automatically dropped by the device-mapper, and any attempt to mount or read it will fail. The original logical volume remains fully functional and unaffected, but the snapshot must be recreated to perform a new backup.

Answer

The original volume becomes read-only.

Answer

The backup completes successfully but data may be inconsistent.

Answer

The original volume is automatically extended.

Question 10

Which two statements are true about LVM snapshots? (Choose two.)

Accepted Answer

Snapshots use copy-on-write technology.. Option C is correct because LVM snapshots use copy-on-write (COW) technology, which means that only the data blocks that are changed after the snapshot is created are copied to the snapshot volume. This makes snapshots space-efficient, as they do not duplicate the entire original volume at creation time.

Answer

Snapshots require the same amount of space as the original volume.

Answer

Snapshots are read-only by default.

Answer

Snapshots are only supported on ext4 filesystems.

Question 11

Refer to the exhibit. The administrator wants to extend the /data filesystem by an additional 10GB. The volume group vg_data has only 1GB of free physical extents. Which action should be taken first?

Accepted Answer

Add /dev/sdc as a physical volume and extend vg_data.. The /data filesystem needs an additional 10GB, but vg_data has only 1GB of free physical extents. To extend the logical volume, the volume group must have sufficient free physical extents. Adding /dev/sdc as a physical volume and extending vg_data increases the pool of physical extents, making the required space available. This is the correct first step because you cannot extend a logical volume beyond the available free extents in its volume group.

Answer

Delete the /backup logical volume to free space.

Answer

Reduce the size of /backup to free space in vg_data.

Answer

Create a new logical volume from the free space in vg_data.

Question 12

A system administrator needs to mount an ext4 filesystem with the options 'noatime' and 'errors=remount-ro'. Which mount command is correct?

Accepted Answer

mount -o noatime,errors=remount-ro /dev/sda1 /mnt. Option D is correct because the `mount -o noatime,errors=remount-ro /dev/sda1 /mnt` command uses a single `-o` flag with a comma-separated list of mount options, which is the proper syntax for specifying multiple options. The `noatime` option disables updating the access time on reads, and `errors=remount-ro` tells the kernel to remount the filesystem as read-only if an I/O error is encountered, both of which are valid ext4 mount options.

Answer

mount -o noatime,errors=remount /dev/sda1 /mnt

Answer

mount -o noatime -o errors=remount-ro /dev/sda1 /mnt

Answer

mount -o atime=no,errors=remount-ro /dev/sda1 /mnt

Question 13

A database server is running out of space in its /var/lib/mysql directory. The system admin wants to add a new 100GB disk to increase storage. Which of the following steps should be performed to mount the new filesystem at /var/lib/mysql without data loss?

Accepted Answer

Partition the disk, create a filesystem, mount it at a temporary mount point, copy existing data from /var/lib/mysql to the new filesystem, unmount /var/lib/mysql (if it's a mount), mount the new filesystem at /var/lib/mysql, and update /etc/fstab.. Option D is correct because it ensures no data loss by first copying existing data to the new filesystem mounted at a temporary point, then unmounting the old mount (if any) and remounting the new filesystem at /var/lib/mysql. This preserves the existing database files and allows the new disk to be used without disrupting the directory structure. The /etc/fstab update ensures the mount persists across reboots.

Answer

Add the new disk as an LVM physical volume, extend the volume group, extend the logical volume containing /var/lib/mysql, and then resize the filesystem.

Answer

Partition the disk, create a filesystem, add an entry in /etc/fstab, and reboot the server.

Answer

Partition the disk, create a filesystem, mount it directly to /var/lib/mysql, and then move the existing data into place.

Question 14

After creating an XFS filesystem on /dev/sdb1, an admin mounts it and writes data. Later, they run 'xfs_info /mnt/data' and see the filesystem was created with default settings. What is the default inode size for XFS on a typical Linux system?

Accepted Answer

256 bytes. The default inode size for XFS on a typical Linux system is 256 bytes. This is set at filesystem creation time and provides a balance between supporting extended attributes (like ACLs and SELinux contexts) and minimizing metadata overhead. The `xfs_info` command confirms the default settings, which include this 256-byte inode size.

Answer

512 bytes

Answer

128 bytes

Answer

4096 bytes

Question 15

You are a systems administrator at a company that uses a centralized LDAP server for authentication, but also maintains local users for emergency access. Recently, the compliance team mandated that all service accounts must have passwords that expire every 90 days. You have a local service account 'svc_backup' with UID 2000 and GID 2000. The account is used by a backup script that runs nightly. You have updated the password aging policy but the account still shows 'Password expires : never' when you run 'chage -l svc_backup'. You suspect that the account was created without an expiry date. Which command would you use to force the password to expire 90 days from now and also ensure that the account's password is changed at the next login?

Accepted Answer

chage -M 90 -d 0 svc_backup. Option A is correct. chage -M 90 sets maximum days to 90, and -d 0 forces immediate password change. Option B uses passwd -x which sets max days but does not force immediate change. Option C sets account expiry, not password expiry. Option D sets warning and inactive days but does not enforce max days or immediate change.

Answer

usermod -e $(date -d '+90 days' +%Y-%m-%d) svc_backup

Answer

passwd -x 90 svc_backup

Answer

chage -W 7 -I 30 svc_backup