LFCS Practice Test 21 — 15 Questions

Question 1

A system administrator needs to change the group ownership of a file to 'developers' and set the setgid bit on a directory. Which two commands accomplish these tasks? (Choose two.)

Accepted Answer

chmod g+s dir. Option A, 'chmod g+s dir', is correct because the g+s symbolic mode sets the setgid bit on the directory, causing new files and subdirectories created inside it to inherit the directory's group ownership. Option D, 'chown :developers file', is correct because omitting the user and specifying only ':developers' changes the file's group ownership to the 'developers' group while leaving the owner unchanged. Option B, 'chmod u+s dir', is wrong because u+s sets the setuid bit on the owner, not the setgid bit, and setuid on a directory is generally ignored on Linux. Option C, 'chown developers: file', is wrong because it sets the user owner to 'developers' rather than the group owner. Option E, 'chmod g+s file', is wrong because the task requires setting setgid on a directory, not on a file.

Answer

chmod u+s dir

Answer

chown developers: file

Answer

chmod g+s file

Question 2

Which THREE of the following statements about Linux file permissions are correct?

Accepted Answer

The command 'chmod 400 secret.txt' sets read-only permission for the owner only.. Option B is correct because chmod 400 secret.txt assigns the octal value 4 (read) to the owner and 0 (no permissions) to group and others, producing r--------, i.e., read-only for the owner only. Option C is correct because chmod 755 file sets owner to 7 (rwx), group to 5 (r-x), and others to 5 (r-x), yielding rwxr-xr-x. Option D is correct because chmod u+x script.sh uses the symbolic mode u+x to add execute permission for the file's owner without altering other permission bits. Option A is wrong because a+w adds write permission for all (user, group, other), not removes it; removal would be a-w. Option E is wrong because chmod 644 yields rw-r--r--, not rw-rw-rw- (which would be 666).

Answer

The command 'chmod a+w file' removes write permission for all.

Answer

The command 'chmod 644 file' sets permissions to rw-rw-rw-.

Question 3

Which TWO commands can be used to display the current working directory?

Accepted Answer

pwd. Option B, `pwd`, is correct because it is the dedicated shell builtin/utility that prints the absolute pathname of the current working directory. Option D, `echo $PWD`, is correct because the shell maintains the `PWD` environment variable holding the current working directory, and `echo` expands it to display that path. Option A, `which pwd`, only locates the executable or builtin for `pwd` and prints its path rather than the working directory. Option C, `date`, displays the current system date and time, and option E, `whoami`, prints the effective username — neither relates to the working directory.

Answer

which pwd

Answer

date

Answer

whoami

Question 4

Which TWO commands can be used to display the contents of a text file that has been compressed with gzip without decompressing it to disk?

Accepted Answer

zcat file.gz. Option C, zcat file.gz, is correct because zcat is functionally equivalent to gunzip -c and writes the decompressed contents of a gzip file directly to standard output, leaving no decompressed file on disk. Option D, gunzip -c file.gz, is correct because the -c (--stdout) flag tells gunzip to send the decompressed data to standard output instead of replacing the .gz file with an uncompressed one. Option A, xzcat file.gz, is wrong because xzcat handles files compressed with xz/lzma, not gzip format. Option B, gzip -l file.gz, is wrong because -l only lists the compressed and uncompressed sizes and ratio; it does not display the file's contents. Option E, bzcat file.gz, is wrong because bzcat decompresses bzip2 files, not gzip files.

Answer

xzcat file.gz

Answer

gzip -l file.gz

Answer

bzcat file.gz

Question 5

Which THREE commands can display the current CPU utilization statistics on a Linux system?

Accepted Answer

top. Option B, top, is correct because it is an interactive process viewer that continuously reports CPU utilization statistics, including per-core and aggregate usage, load average, and per-process CPU consumption. Option C, sar -u, is correct because the -u flag of the sar command from the sysstat package reports CPU utilization statistics (user, system, iowait, idle percentages) either for the current day or a specified interval. Option D, mpstat -P ALL, is correct because mpstat from the sysstat package with -P ALL displays per-processor CPU utilization statistics, showing each individual CPU core's usage percentages. Option A, free, is incorrect because it only reports memory and swap usage, not CPU statistics. Option E, uptime, is incorrect because it only shows the current time, system uptime, number of logged-in users, and load averages, without detailed CPU utilization percentages.

Answer

free

Answer

uptime

Question 6

An administrator is configuring LVM and wants to display information about physical volumes, volume groups, and logical volumes. Which two commands provide this information? (Choose two.)

Accepted Answer

pvdisplay, vgdisplay, lvdisplay. Option D is correct because pvdisplay, vgdisplay, and lvdisplay are the LVM reporting commands that print detailed information about physical volumes, volume groups, and logical volumes respectively, including attributes such as size, UUID, PE size, and allocation policy. Option E is also correct because pvs, vgs, and lvs are the LVM reporting commands that produce concise, column-oriented summaries of physical volumes, volume groups, and logical volumes, making them ideal for quickly displaying this information. Option A is incorrect because pvscan, vgscan, and lvscan scan for and activate LVM metadata/devices rather than displaying detailed configuration information. Option B is incorrect because pvck, vgck, and lvck check and repair LVM metadata consistency, not report volume information. Option C is incorrect because pvcreate, vgcreate, and lvcreate create physical volumes, volume groups, and logical volumes rather than displaying information about them.

Answer

pvscan, vgscan, lvscan

Answer

pvck, vgck, lvck

Answer

pvcreate, vgcreate, lvcreate

Question 7

Which TWO commands can be used to check whether a systemd service is currently running?

Accepted Answer

systemctl status service. Option A, `systemctl status service`, is correct because it queries the service's runtime state and displays the Active line (e.g., `Active: active (running)`), directly showing whether the unit is currently running. Option C, `systemctl is-active service`, is correct because it prints the unit's active state (typically `active` or `inactive`) and returns exit code 0 when the service is running, making it ideal for scripted checks. Option B, `systemctl list-units --state=running`, lists all running units system-wide rather than confirming one specific service, so it is not a targeted check. Option D, `systemctl is-enabled service`, only reports whether the unit is enabled to start at boot, not whether it is currently running. Option E, `systemctl show service`, dumps all unit properties by default and does not by itself answer the running-state question without filtering for ActiveState.

Answer

systemctl list-units --state=running

Answer

systemctl is-enabled service

Answer

systemctl show service

Question 8

An administrator needs to configure a service to run as a non-root user for security reasons. Which systemd unit file directive accomplishes this?

Accepted Answer

User=myuser. The `User=` directive in a systemd unit file specifies the user (by name or UID) under which the service process runs. By setting `User=myuser`, the service executes with the privileges of that non-root user, reducing the attack surface and adhering to the principle of least privilege. This is the standard systemd mechanism for dropping root privileges for a service.

Answer

AmbientCapabilities=CAP_NET_BIND_SERVICE

Answer

DynamicUser=yes

Answer

Group=myuser

Question 9

A user needs to view the contents of a large text file one screen at a time. Which command is best for this?

Accepted Answer

less file.txt. `less` is a terminal pager that allows forward and backward navigation through a file, making it ideal for viewing large text files one screen at a time. Unlike `more`, `less` supports scrolling both up and down, and it does not load the entire file into memory, which is efficient for large files.

Answer

nl file.txt

Answer

more file.txt

Answer

cat file.txt

Question 10

Which bonding mode provides high availability without requiring switch configuration?

Accepted Answer

mode 1 (active-backup). Mode 1 (active-backup) provides high availability by designating one NIC as active and the others as standby, with automatic failover if the active link fails. It requires no special switch configuration because it does not use any link aggregation protocol or load-balancing algorithm that depends on switch-side settings.

Answer

mode 4 (802.3ad)

Answer

mode 6 (balance-alb)

Answer

mode 0 (balance-rr)

Question 11

A system administrator needs to identify all available block devices on a Linux server. Which two commands can be used to accomplish this? (Choose two.)

Accepted Answer

lsblk. lsblk (C) is correct because it reads /sys/block and udev data to list all block devices in a tree view, showing disks, partitions, and their sizes, types, and mountpoints regardless of whether they are mounted. fdisk -l (E) is correct because it enumerates every block device in /proc/partitions and prints the partition table of each disk, making it a standard way to discover all available block devices. blkid (A) only reports devices that already have a filesystem or swap signature and their UUID/LABEL, so it misses unformatted or otherwise unrecognized block devices. mount (B) shows only currently mounted filesystems, not all block devices. df -h (D) reports disk space usage of mounted filesystems only, so it also fails to reveal unmounted or unformatted block devices.

Answer

blkid

Answer

mount

Answer

df -h

Question 12

A Linux administrator needs to configure VLAN tagging on a network bridge to isolate traffic from different virtual machines. The physical interface is eth0, and VLAN ID 100 should be accessible via the bridge br0. Which set of commands correctly creates this configuration using the ip command?

Accepted Answer

ip link add link eth0 name eth0.100 type vlan id 100; ip link add br0 type bridge; ip link set eth0.100 master br0; ip link set br0 up. It first creates a VLAN interface (eth0.100) on top of physical interface eth0 with VLAN ID 100 using `ip link add link eth0 name eth0.100 type vlan id 100`. It then creates a bridge (br0) with `ip link add br0 type bridge`, attaches the VLAN interface to the bridge as a port with `ip link set eth0.100 master br0`, and finally brings the bridge up. This sequence ensures that traffic tagged with VLAN 100 on eth0 is properly forwarded through the bridge to virtual machines, while untagged or other VLAN traffic is isolated.

Answer

ip link add br0 type bridge; ip link set eth0 master br0; ip link set br0 up

Answer

ip link add eth0.100 link eth0 type vlan id 100; ip link set eth0.100 master br0; ip link add br0 type bridge

Answer

ip link add name br0 type bridge; ip link add link br0 name vlan100 type vlan id 100; ip link set eth0 master br0

Question 13

A system administrator runs 'ss -tuln' and sees that port 80 is listening. What does the 'u' option represent?

Accepted Answer

UDP. In the `ss` command, the `-u` option filters output to show only UDP sockets. Since the question shows `ss -tuln`, which combines `-t` (TCP), `-u` (UDP), `-l` (listening), and `-n` (numeric), the `u` specifically represents UDP. This is confirmed by the `ss` man page and standard Linux networking tools.

Answer

User

Answer

Unix sockets

Answer

Unicast

Question 14

Which THREE of the following are valid directives for the [Service] section of a systemd unit file?

Accepted Answer

Type. Option A (Type) is correct because Type is a [Service]-section directive that tells systemd how to start and track the process (e.g., simple, forking, oneshot, notify, dbus, idle), which is essential for correct service supervision. Option C (User) is correct because User is a [Service]-section directive that sets the UNIX account the service process runs as, a common hardening and permission control. Option D (ExecStart) is correct because ExecStart is a [Service]-section directive that specifies the command line to launch the service, and it is the primary way systemd knows what to execute. Option B (Requires) does not belong because Requires is a dependency directive valid in the [Unit] section, not [Service]. Option E (Description) does not belong because Description is a metadata directive valid in the [Unit] section, not [Service].

Answer

Requires

Answer

Description

Question 15

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