Free LFCS practice test: 30 questions with answers

du -sh with a glob reports the total size of each item in human-readable form. df reports filesystem free space rather than per-directory usage, ls -lh shows file sizes without totals, and lsblk lists block devices.

find with -type f and -mtime -1 selects regular files modified in the last day. locate uses a prebuilt database and does not filter by modification time, grep searches file contents, and ls has no recent option.

cat prints the whole file and less pages through it, and both read the file without modifying it. touch changes timestamps or creates empty files, mkdir creates directories, and chmod changes permissions.

ln -s creates a symbolic link, and the first argument is the target while the second is the link name. A plain ln creates a hard link, which cannot point to a directory, cp -s is not a link command, and mklink is a Windows command.

uniq only collapses adjacent duplicates, so the input must be sorted first, and uniq -c adds counts before a reverse numeric sort orders by frequency. The other pipelines skip the sort or use commands that do not exist.

Owner rwx is 7, group r-x is 5, and others --- is 0, which gives 750. 755 gives others read and execute, 640 removes execute for the owner and group, and 700 removes all group access.

systemctl is-enabled reports whether a unit is enabled to start at boot. The other options are not systemctl subcommands for this purpose, and systemd-analyze check validates unit file syntax.

SIGKILL cannot be caught, blocked or ignored, so the kernel terminates the process. SIGHUP, SIGINT and SIGQUIT can be caught or ignored by a process, so they do not guarantee termination.

top shows live processes sorted by CPU by default, and ps with --sort=-%cpu prints a static list ordered from highest CPU use. Sorting by PID does not order by CPU, and df and free report disk and memory.

journalctl -b limits output to the current boot, and -b with an offset selects other boots. The other options are not valid selectors for the current boot.

Cron fields are minute, hour, day of month, month and day of week, so 30 6 * * 1-5 runs at 06:30 Monday to Friday. The other entries reverse the time, run every day, or select days of the month instead.

Restart=on-failure in the [Service] section restarts the service when it exits abnormally. The other keys are not systemd unit directives.

ss -tlnp shows listening TCP sockets with numeric addresses and process information when run with sufficient privilege. ifconfig and route do not show listening sockets, and ping -l sets a preload count rather than listing sockets.

/etc/hosts provides static name-to-address mappings used by the resolver depending on the lookup order. resolv.conf defines DNS servers, services maps port names to numbers, and nsswitch.conf sets the lookup order rather than the mappings.

ip addr add assigns an address to an interface until reboot or until it is removed. The other options use invalid syntax, and route add does not configure an interface address.

ufw allow OpenSSH uses the application profile that ufw ships for SSH, which is the simplest correct rule. ufw open and ufw enable ssh only are not valid ufw syntax, and iptables -A SSH uses a chain name that does not exist.

traceroute reports each hop between the host and the destination with its round-trip time. dig queries DNS records, ping -c 1 sends one echo request, and nc -z tests whether a port is open.

dig and host query DNS servers and show the records returned for a name. ip route show lists routing table entries, ssh-keygen -l prints key fingerprints, and nmcli dev status shows device state rather than name lookups.

usermod -aG appends the group to the supplementary list, which keeps the existing memberships. Omitting -a replaces the whole list, groupadd creates a group rather than adding a user, and useradd -g changes the primary group when the account is created.

/etc/shadow stores password hashes and aging data, readable only by root. /etc/passwd holds account fields, /etc/group holds group membership, and /etc/gshadow holds group password data.

chage -l lists the password aging information for an account. passwd --expire forces a password change, and id and groups show identity and group membership rather than aging data.

visudo checks the sudoers syntax before saving, which prevents lockouts, and narrow command grants follow least privilege. A plain editor risks syntax errors, blanket NOPASSWD grants weaken control, and storing passwords in a message file is unsafe.

usermod -L locks the password by prefixing the stored hash with an invalid character, which blocks password login. -e sets an expiry date rather than locking, and userdel and groupmod do not lock user passwords.

useradd -m creates the home directory and -G adds the supplementary group. -g would make analysts the primary group, and newuser and the last option are not valid account creation commands with these arguments.

lsblk prints block devices as a tree with sizes and mount points. blkid shows filesystem identifiers, fdisk -l lists partition tables without the mount tree, and du reports directory sizes.

mkfs.ext4 creates an ext4 filesystem on the partition, which destroys existing data on it. fsck checks a filesystem, tune2fs adjusts its parameters, and ext5 is not a Linux filesystem type.

/etc/fstab defines persistent mounts, and a UUID stays the same even if device names change. /etc/mtab records current mounts and is managed by the system, /etc/hostname holds the host name, and /dev/fstab is not used.

lvcreate with -L sets the size, -n sets the name, and the volume group comes last. The other arguments are in the wrong order, and vgcreate and pvcreate create volume groups and physical volumes rather than logical volumes.

mdadm --create builds the mirrored array from two devices, and recording the scan output in mdadm.conf keeps the array assembled at boot. Formatting, mounting and extending a logical volume are later steps, not part of creating the RAID array.

resize2fs grows an ext4 filesystem to fill its device after the volume has been extended. xfs_growfs applies to XFS, tune2fs -r changes reserved blocks, and fsck checks rather than grows the filesystem.