LFCS Practice Test 19 — 15 Questions

Question 1

A server runs a custom application that listens on TCP port 8080. The administrator wants to ensure the application starts automatically on boot and restarts if it crashes. Which systemd unit file directive should be used to achieve the restart behavior?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Restart=on-failure. The `Restart=on-failure` directive in a systemd unit file instructs systemd to automatically restart the service unit when it exits with a non-zero exit code, is terminated by a signal (including SIGKILL), or times out. This directly satisfies the requirement for the application to restart if it crashes, as a crash typically results in an unclean exit that triggers the restart condition.

Answer

RestartSec=5

Answer

Type=notify

Answer

RemainAfterExit=yes

Question 2

A system administrator needs to set up software RAID1 on a server for /data. The available disks are /dev/sdb (500GB) and /dev/sdc (1TB). What is the maximum usable capacity of the RAID1 array?

Accepted Answer

500GB. RAID1 (mirroring) writes identical data to all disks in the array, so the usable capacity is limited by the smallest disk. With /dev/sdb at 500GB and /dev/sdc at 1TB, the maximum usable capacity is 500GB. The remaining space on /dev/sdc (500GB) is unusable in the RAID1 array because it cannot be mirrored.

Answer

250GB

Answer

1TB

Answer

1.5TB

Question 3

To view the system's default runlevel (target) at boot, which command is used on a systemd-based system?

Accepted Answer

systemctl get-default. On systemd-based systems, the default target (analogous to runlevel) is managed by systemctl. The command `systemctl get-default` queries the symlink at `/etc/systemd/system/default.target` to display which target is set to boot by default, making it the correct way to view the system's default boot target.

Answer

systemd-analyze

Answer

runlevel

Answer

cat /etc/inittab

Question 4

Given the network interface configuration in the exhibit, which command should be run to apply the configuration without rebooting?

Accepted Answer

ifup eth0. The `ifup eth0` command reads the configuration file for the eth0 interface (typically `/etc/sysconfig/network-scripts/ifcfg-eth0` on RHEL/CentOS) and applies the settings (IP address, netmask, gateway, etc.) without requiring a system reboot. This is the standard way to activate a network interface with its configured parameters on Linux systems using the legacy network scripts.

Answer

systemctl restart network

Answer

ifconfig eth0 down && ifconfig eth0 up

Answer

ip link set eth0 up

Question 5

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 6

A server running Ubuntu 20.04 uses netplan for network configuration. The admin wants to set a static IP address 10.0.0.100/24 on interface enp0s3 with gateway 10.0.0.1 and DNS servers 8.8.8.8 and 8.8.4.4. Which YAML configuration is correct?

Accepted Answer

network:
  version: 2
  ethernets:
    enp0s3:
      addresses:
        - 10.0.0.100/24
      gateway4: 10.0.0.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]. It uses the proper Netplan YAML syntax: `addresses` as a list, `gateway4` for the IPv4 default gateway, and `nameservers` with an `addresses` list. This matches the required static IP 10.0.0.100/24, gateway 10.0.0.1, and DNS servers 8.8.8.8 and 8.8.4.4.

Answer

network:
  version: 2
  ethernets:
    enp0s3:
      addresses:
        - 10.0.0.100/24
      gateway: 10.0.0.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]

Answer

network:
  version: 2
  ethernets:
    enp0s3:
      address: 10.0.0.100/24
      gateway4: 10.0.0.1
      dns-nameservers: 8.8.8.8 8.8.4.4

Answer

network:
  ethernets:
    enp0s3:
      addresses: 10.0.0.100/24
      gateway4: 10.0.0.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]

Question 7

A system administrator wants to configure a custom service to start automatically at boot. Which command accomplishes this?

Accepted Answer

systemctl enable custom.service. The `systemctl enable custom.service` command creates the necessary symlinks in the systemd unit file directories (e.g., `/etc/systemd/system/multi-user.target.wants/`) so that the service is automatically started at boot. This is the correct method to configure a custom service for automatic startup in a systemd-based Linux distribution.

Answer

systemctl daemon-reload custom.service

Answer

systemctl reenable custom.service

Answer

systemctl start custom.service

Question 8

A developer reports that a compiled binary 'app' fails to execute with 'Permission denied' error when run from a mounted directory '/mnt/software'. The binary has execute permissions for all users. What is the most likely cause?

Accepted Answer

The filesystem is mounted with the 'noexec' option.. The 'noexec' mount option prevents execution of any binary files on the filesystem, regardless of their file permissions. When a filesystem is mounted with 'noexec', the kernel will refuse to execute binaries from that mount point, returning 'Permission denied' even if the binary has execute permissions for all users. This is a common security measure for mounted directories like /mnt/software to prevent unauthorized code execution.

Answer

SELinux is blocking execution.

Answer

The binary is linked against missing libraries.

Answer

The binary is setuid but owned by a user other than root.

Question 9

A server has two NICs bonded in mode 1 (active-backup). If the active NIC fails, what occurs?

Accepted Answer

Traffic automatically switches to the backup NIC with minimal interruption. In bonding mode 1 (active-backup), only one NIC is active at a time while the other remains in standby. When the active NIC fails, the bonding driver automatically fails over to the backup NIC by reassigning the MAC address and IP to the backup interface, typically within a few milliseconds. This ensures minimal interruption to network traffic without requiring manual intervention.

Answer

Both NICs continue to pass traffic simultaneously

Answer

The bond interface goes down until an administrator intervenes

Answer

The system disables the bond and uses a single NIC

Question 10

A user wants to find the location of the 'grep' binary. Which command should they use?

Accepted Answer

which grep. The 'which' command is specifically designed to locate the binary (executable) of a command by searching the directories listed in the user's PATH environment variable. Option B, 'which grep', will output the full path to the grep binary, such as '/usr/bin/grep', directly answering the user's request.

Answer

man grep

Answer

uname -a

Answer

grep -r 'grep' /usr/bin

Question 11

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 are implemented using copy-on-write (COW): when data on the origin logical volume is modified, the original block is copied to the snapshot's COW space before being overwritten, so the snapshot preserves the point-in-time state. Option D is correct because a snapshot can be mounted and its contents copied back to the origin (or the origin can be reverted from the snapshot with lvconvert --merge), making it a valid mechanism for restoring the original volume. Option A is wrong because a snapshot only needs enough space to hold changed blocks, not a full copy of the origin. Option B is wrong because LVM snapshots are writable by default, though they are typically used read-only. Option E is wrong because LVM snapshots operate at the block-device layer and are filesystem-agnostic, working with ext4, XFS, and others.

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 12

A system administrator needs to securely transfer files between two Linux servers using port 22. The administrator uses the following command: 'scp file.txt user@remote:/tmp/'. The transfer fails with the error 'Permission denied (publickey)'. What is the most likely cause?

Accepted Answer

The client's public key is not in the remote user's authorized_keys file.. The error 'Permission denied (publickey)' indicates that the SSH key-based authentication failed. SCP uses SSH for transport, and by default, SSH on the remote server checks the client's public key against the remote user's ~/.ssh/authorized_keys file. If the client's public key is not listed there, the SSH server rejects the connection, causing the SCP transfer to fail.

Answer

The remote server does not have SSH installed.

Answer

The SSH service is not running on the remote server.

Answer

The remote server's firewall is blocking port 22.

Question 13

An administrator has added a new disk (/dev/sdb) to a Linux system. The disk is to be used as a physical volume in an existing volume group 'vg_data'. Which sequence of commands should be executed to make the disk available to the volume group?

Accepted Answer

pvcreate /dev/sdb; vgextend vg_data /dev/sdb. It first initializes the disk as a physical volume using `pvcreate`, which writes LVM metadata to /dev/sdb, and then extends the existing volume group 'vg_data' with `vgextend`, adding the new PV to the VG. This is the standard two-step process for adding a new disk to an existing LVM volume group.

Answer

fdisk /dev/sdb; pvcreate /dev/sdb; vgextend vg_data /dev/sdb

Answer

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

Answer

vgcreate /dev/sdb; vgextend vg_data /dev/sdb

Question 14

Which tool is the recommended method for persistently configuring network interfaces in RHEL 8?

Accepted Answer

Using nmcli commands. In RHEL 8, NetworkManager is the default networking daemon, and 'nmcli' is the recommended command-line tool for persistently configuring network interfaces. Unlike temporary 'ip' commands, nmcli writes configuration to NetworkManager connection profiles, ensuring changes survive reboots. Red Hat officially deprecates direct editing of ifcfg files in RHEL 8 and uses NetworkManager as the primary interface.

Answer

Using the 'ip' command with persistent flags

Answer

Editing /etc/sysconfig/network-scripts/ifcfg-* files directly

Answer

Using systemd-networkd configuration files

Question 15

A large e-commerce platform runs on a database server that uses LVM thin provisioning. The thin pool is overcommitted at 200% (pool size 1TB, thin volumes total 2TB). Suddenly, the database reports write errors and performance degrades drastically. The administrator checks the system and finds that the thin pool is completely full. What is the immediate effect on the thin volumes, and what should the administrator do to restore normal operation without data loss?

Accepted Answer

The volumes become read-only; administrator must add more physical storage to the volume group and extend the thin pool.. When an LVM thin pool is completely full, the kernel cannot allocate new blocks for any thin volume, so all thin volumes in that pool are automatically switched to read-only mode to prevent data corruption. The immediate fix is to add physical storage to the volume group (e.g., vgextend) and then extend the thin pool (lvextend) so that new blocks can be allocated. This restores write capability without data loss because the volumes were never corrupted—they were simply protected by the read-only state.

Answer

The volumes continue to operate but with severe slowdown; administrator must delete unnecessary snapshots.

Answer

The volumes become corrupted; administrator must restore from backup.

Answer

The volumes automatically extend the pool using metadata space; no action needed.