LFCS Practice Test 17 — 15 Questions

Question 1

A user named 'charlie' has just been added to the 'devops' group. However, when 'charlie' runs 'sudo -l', no sudo entries are shown. What is the most likely cause?

Accepted Answer

'charlie' must log out and log back in for the group change to take effect.. When a user is added to a new group, the group membership is only applied to new login sessions. The `sudo -l` command checks the user's current group memberships, which are cached at login time. Since 'charlie' was added to the 'devops' group while already logged in, the new group membership is not reflected until 'charlie' logs out and logs back in, or uses `newgrp` or `sg` to start a new session with the updated groups.

Answer

'charlie' is not listed by name in the sudoers file.

Answer

'charlie' is also a member of another group that restricts sudo.

Answer

The systemctl command is not executable by 'charlie'.

Answer

The sudoers file has a syntax error.

Question 2

An administrator deploys a new custom service using a unit file called myapp.service. The service needs to start automatically at system boot. Which command should the administrator run to achieve this?

Accepted Answer

systemctl enable myapp.service. The `systemctl enable` command creates the necessary symlinks in the systemd unit configuration directories (e.g., `/etc/systemd/system/multi-user.target.wants/`) to ensure the service is started automatically at boot. This is the correct method to enable a service to start on boot in a systemd-based Linux system.

Answer

systemctl start myapp.service

Answer

systemctl add-wants myapp.service

Answer

systemctl daemon-reload myapp.service

Question 3

An administrator needs to delete user 'obsolete' and remove its home directory and mail spool. Which command should be used?

Accepted Answer

userdel -r obsolete. The correct command is `userdel -r obsolete` because the `-r` flag removes the user's home directory and mail spool in addition to deleting the user account. This matches the requirement to delete the user 'obsolete' along with its home directory and mail spool, as specified in the question.

Answer

userdel -f obsolete

Answer

userdel obsolete

Answer

groupdel obsolete

Question 4

Which TWO commands can be used to display the routing table on a Linux system?

Accepted Answer

route -n. The `route -n` command displays the kernel IP routing table with numeric addresses, showing destination, gateway, netmask, and interface. The `ip route show` command is the modern equivalent from the iproute2 suite, which also displays the routing table with more detailed information. Both are standard tools for viewing routing decisions on a Linux system.

Answer

ip addr show

Answer

arp -a

Answer

ss -tln

Question 5

A Linux server at a hosting provider uses a software RAID 5 array with three 2 TB disks (sda, sdb, sdc) configured as /dev/md0, hosting a large ext4 filesystem. The server experiences a performance degradation and I/O errors. The administrator checks /proc/mdstat and sees that /dev/sda is marked as failed. The remaining two disks are still active. The administrator has a spare disk /dev/sdd of the same size. The filesystem is sparse and can tolerate downtime. What is the most appropriate course of action to restore the array to a fully functional state with redundancy?

Accepted Answer

Run 'mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda', then 'mdadm --manage /dev/md0 --add /dev/sdd'.. The correct procedure is to mark the failed disk as failed (if not already), remove it from the array, then add the spare disk /dev/sdd. This allows mdadm to rebuild the RAID 5 array onto the new disk, restoring redundancy. The commands 'mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda' followed by 'mdadm --manage /dev/md0 --add /dev/sdd' accomplish this safely.

Answer

Recreate the RAID 5 array from scratch using all three healthy disks (sdb, sdc, sdd) and restore data from backup.

Answer

Run 'mdadm --manage /dev/md0 --add /dev/sdd' to directly add the new disk and let the array rebuild automatically.

Answer

Use LVM to mirror the two healthy disks and ignore the failed one, ensuring data redundancy.

Question 6

An administrator wants to force a user to change their password at next login. Which command should be used?

Accepted Answer

passwd -e user. The `passwd -e user` command immediately expires the user's password, forcing them to change it at the next login. This is the standard method to achieve this requirement on Linux systems.

Answer

passwd -l user

Answer

chage -m 0 user

Answer

usermod -p '!' user

Question 7

An administrator needs to combine two sorted text files, /tmp/a.txt and /tmp/b.txt, into a single sorted stream on standard output while also removing duplicate lines that appear in both files. Which command should be used?

Accepted Answer

sort -u /tmp/a.txt /tmp/b.txt. Sorting both files together with duplicate suppression yields the union of their lines in order, which matches the request. Merge mode preserves duplicates, uniq cannot read two inputs and would clobber the second path, and comm -12 returns only the shared lines, so none of those alternatives produce the required combined, deduplicated stream.

Answer

sort -m /tmp/a.txt /tmp/b.txt

Answer

comm -12 /tmp/a.txt /tmp/b.txt

Answer

uniq /tmp/a.txt /tmp/b.txt

Question 8

An administrator manages a server whose /home directory resides on the logical volume /dev/vg_users/lv_home. Usage reports show the LV is 98% full, and the volume group vg_users has 40 GB of free extents. The filesystem is ext4. Which sequence correctly expands the usable space to /home?

Accepted Answer

lvextend -L +20G /dev/vg_users/lv_home && resize2fs /dev/vg_users/lv_home. Extending an ext4 filesystem on LVM requires enlarging the logical volume first with lvextend, then expanding the filesystem with resize2fs. The volume group already has free extents, so no additional physical volume is needed. The filesystem can be resized online while /home remains mounted.

Answer

resize2fs /dev/vg_users/lv_home 20G && lvextend -L +20G /dev/vg_users/lv_home

Answer

lvextend -L +20G /dev/vg_users/lv_home && xfs_growfs /home

Answer

vgextend vg_users /dev/vg_users/lv_home && resize2fs /dev/vg_users/lv_home

Question 9

A system administrator notices that '/var/log/syslog' has grown very large and is consuming significant disk space. The administrator wants to identify the largest log files in the '/var/log' directory hierarchy. Which command should the administrator use?

Accepted Answer

du -ah /var/log | sort -hr | head -10. `du -ah /var/log` calculates the disk usage of all files and directories in `/var/log` in human-readable format, then `sort -hr` sorts them by size in descending order, and `head -10` shows the top 10 largest entries. This directly identifies the largest log files in the hierarchy, which is exactly what the administrator needs.

Answer

find /var/log -size +100M -exec ls -lh {} \;

Answer

df -h /var/log

Answer

ls -lhS /var/log

Question 10

An administrator must ensure that a Linux router forwards IPv4 packets between its two interfaces, eth0 and eth1, without rebooting. Which command enables this behavior immediately?

Accepted Answer

sysctl -w net.ipv4.ip_forward=1. Enabling IPv4 forwarding requires setting the kernel parameter net.ipv4.ip_forward to 1. The sysctl -w command applies this change at runtime, immediately allowing the router to forward packets between interfaces. Firewall rules and interface states are separate concerns; they do not substitute for the kernel forwarding parameter.

Answer

iptables -A FORWARD -j ACCEPT

Answer

echo 1 > /proc/sys/net/ipv4/ip_forward

Answer

ip link set eth0 up && ip link set eth1 up

Question 11

A user reports that they cannot execute a file even though they are in the file's group. The file has permissions 644 and group ownership 'staff'. The user is a member of 'staff'. What is the likely issue?

Accepted Answer

The file lacks execute permission for the group. The file has permissions 644, which means the owner has read/write (6), the group has read-only (4), and others have read-only (4). Since the user is a member of the group 'staff' but not the owner, they fall under the group permission class. The group lacks execute permission (the 'x' bit), so the user cannot execute the file. Execute permission is required to run a file as a command or script, regardless of group membership.

Answer

The file does not have the setgid bit

Answer

The user's primary group is not 'staff'

Answer

The user is not the owner of the file

Question 12

Order the steps to set up passwordless SSH key-based authentication.

Accepted Answer

Generate SSH key pair using ssh-keygen, then copy the public key to the remote server using ssh-copy-id, then set correct permissions on the remote server (chmod 700 ~/.ssh and chmod 600 ~/.ssh/authorized_keys), then test the SSH login without a password prompt.. Key generation, copying, and testing are essential; permissions and file verification ensure security.

Answer

Copy the public key to the remote server using ssh-copy-id first, then generate the SSH key pair, then set permissions, then test login.

Answer

Generate SSH key pair, then set permissions on the remote server, then test login, then copy the public key.

Answer

Generate SSH key pair, then set permissions on the local machine, then copy the public key to the remote server, then test login.

Question 13

A system running RHEL 8 experiences intermittent crashes. After reboot, 'journalctl -p err -b -1' outputs: 'PID 1234 (myapp) ended due to signal: KILL'. Which diagnostic step should the administrator perform next?

Accepted Answer

Check journalctl for 'oom-kill' entries or use 'dmesg | grep -i oom'.. The 'PID ended due to signal: KILL' message indicates the process was terminated by a SIGKILL (signal 9), which is commonly sent by the Out-Of-Memory (OOM) killer when the system runs low on memory. Checking journalctl for 'oom-kill' entries or using 'dmesg | grep -i oom' directly confirms whether the OOM killer was responsible, making D the correct next diagnostic step.

Answer

Review logrotate configuration for myapp logs.

Answer

Run strace to capture system calls of myapp before restarting.

Answer

Enable core dumps and reproduce issue.

Question 14

Order the steps to create a new partition on a disk using fdisk.

Accepted Answer

Run 'n' to create a new partition, then specify partition type/number, then specify starting and ending sectors, then run 'w' to write changes.. The correct sequence to create a partition with fdisk is: first use 'n' to create a new partition, then specify the partition type and number (e.g., primary, logical) when prompted, then define the starting and ending sectors, and finally use 'w' to write the changes to the disk. Skipping or reordering steps can lead to errors or unintended configurations.

Answer

Run 'n' to create a new partition, then run 'w' to write changes, then specify partition type/number and sectors.

Answer

First specify partition type/number, then run 'n' to create a new partition, then specify sectors, then run 'w'.

Answer

Run 'n' to create a new partition, then specify sectors, then specify partition type/number, then run 'w'.

Question 15

Refer to the exhibit. The output of 'ip addr show' reveals that eth0 is in state DOWN and has no IPv4 address. Which command is most likely to bring the interface up and obtain an IP via DHCP?

Accepted Answer

ifup eth0. The `ifup` command is a distribution-agnostic tool that reads the interface configuration from files (e.g., `/etc/network/interfaces` on Debian/Ubuntu or `/etc/sysconfig/network-scripts/ifcfg-eth0` on RHEL/CentOS) and brings the interface up while automatically initiating a DHCP client (e.g., dhclient or dhcpcd) to obtain an IPv4 address. This is the standard way to activate a network interface with its configured addressing method, including DHCP, in a single step.

Answer

ip link set eth0 up

Answer

ip route add default via 192.168.1.1 dev eth0

Answer

ip link set dev eth0 up