EX200 Practice Test 12 — 15 Questions

Question 1

Which command displays the UUID of all file systems on the system?

Accepted Answer

blkid. The `blkid` command is the correct choice because it is specifically designed to locate and display block device attributes, including the UUID, filesystem type, and label, for all filesystems on the system. It reads data from the `/dev/disk/by-uuid/` directory and the `udev` database, making it the most direct and reliable tool for querying UUIDs without requiring root privileges for basic output.

Answer

dumpe2fs -h

Answer

lsblk

Answer

fdisk -l

Question 2

A script needs to execute a command that might fail, but the script should continue. The administrator wants to capture the exit status for logging. Which code snippet correctly implements this?

Accepted Answer

./risky_command; rc=$?; echo $rc. It runs the risky command, captures its exit status immediately after in the `$?` variable, and then echoes it for logging. The script continues regardless of the command's success or failure, which meets the requirement. The `$?` variable holds the exit status of the last executed foreground command, so assigning it to `rc` right after `./risky_command` ensures the correct value is stored.

Answer

set -e; ./risky_command; rc=$?; echo $rc

Answer

rc=$? ./risky_command; echo $rc

Answer

./risky_command && rc=$?; echo $rc

Question 3

A user was recently added to the 'testgrp' group using `usermod -aG testgrp user1`. However, when they try to access a file owned by testgrp with permissions 660, they get permission denied. What is the most likely reason?

Accepted Answer

The user did not log out and log back in.. When a user is added to a supplementary group with `usermod -aG`, the group membership change does not take effect in the user's current login session. The user must log out and log back in (or start a new login shell) for the new group to be recognized by the kernel's process credential system. Without this, the user's process lacks the group ID in its supplementary group list, so access to a file with group permissions (660) is denied.

Answer

The user's primary group is not testgrp.

Answer

The file's group owner is not testgrp.

Answer

The file's ACL overrides group permissions.

Question 4

In /etc/fstab, which values in the dump and pass fields enable automatic file system checking at boot?

Accepted Answer

dump=0, pass=1. The `pass` field in `/etc/fstab` controls the order of file system checks at boot. A value of 1 means the root file system is checked first, and a value of 2 or higher means other file systems are checked after root. The `dump` field is for backup utility (dump) and is not related to boot-time checking; it must be 0 to disable dump. Thus, `dump=0, pass=1` enables automatic file system checking (fsck) at boot for the root file system.

Answer

dump=1, pass=0

Answer

dump=0, pass=0

Answer

dump=1, pass=1

Question 5

A container exits immediately with status 1. The administrator runs 'podman logs container' but sees no output. What is the most likely reason for the missing logs?

Accepted Answer

The container binary is missing or has the wrong architecture (exec format error).. When a container exits immediately with status 1 and `podman logs` shows no output, the most common cause is that the container binary is missing or has the wrong architecture (e.g., an x86 binary on an ARM system). This results in an 'exec format error' that prevents the container's entrypoint from executing, so no stdout/stderr is ever written to the logging driver. The container exits before any process runs, leaving the log buffer empty.

Answer

The container's logging driver is not configured to capture stdout.

Answer

The log file is rotated and cleared.

Answer

The container is using a non-standard log location inside the container.

Question 6

The administrator wants to reduce the file system size to 40GB. Which command sequence should be used?

Accepted Answer

It is not possible to shrink an XFS file system. XFS is a high-performance 64-bit journaling file system that does not support online or offline shrinking. Once an XFS file system is created, its size cannot be reduced; the only way to reclaim space is to back up the data, destroy the file system, recreate it at the desired size, and restore the data. Therefore, any attempt to shrink an XFS file system using lvreduce or similar tools will corrupt the file system.

Answer

xfs_repair; lvreduce

Answer

umount /mnt/data; lvreduce -L 40G; mount; xfs_growfs

Answer

lvreduce -L 40G /dev/vg00/lvol0; xfs_growfs

Question 7

Refer to the exhibit. An administrator sees that a user from 192.168.1.101 cannot connect to the SSH server. Based on the log, what is the most probable cause?

Accepted Answer

The client's host key type is not supported by the server. The log shows 'no matching host key type found. Their offer: ssh-rsa'. This indicates the client offered an ssh-rsa host key, but the server's configuration (likely via the `HostKeyAlgorithms` directive in `/etc/ssh/sshd_config`) does not include ssh-rsa. In modern OpenSSH (e.g., RHEL 8/9), ssh-rsa is often disabled by default due to its reliance on SHA-1, which is considered weak. The server requires a different host key type (e.g., rsa-sha2-256, rsa-sha2-512, or ecdsa-sha2-nistp256), causing the connection to fail before authentication even begins.

Answer

The server's firewall is blocking the connection

Answer

The SSH service is not running

Answer

The client's IP is blacklisted

Question 8

A file has been assigned an incorrect SELinux context, preventing a service from accessing it. Which command restores the default SELinux context for that file?

Accepted Answer

restorecon. The `restorecon` command is used to restore the default SELinux security context for a file or directory based on the system's policy store (the file_contexts database). When a file has an incorrect context that prevents a service from accessing it, `restorecon` resets the context to the correct default, allowing the service to access the resource as intended.

Answer

chcon

Answer

fixfiles

Answer

setfiles

Question 9

Refer to the exhibit. A user 'alice' is unable to write to /data directory. What is the most likely reason?

Accepted Answer

The directory permissions restrict access. The exhibit (not shown here) likely displays directory permissions such as 'drwxr-xr-x' or 'drwx------' that do not grant write access to the user 'alice'. In Linux, the write permission (w) on a directory controls whether a user can create, delete, or rename files within it. Since 'alice' lacks write permission on /data, she cannot write to it, regardless of ownership or filesystem space.

Answer

The filesystem is nearly full

Answer

The directory is owned by root and alice is not root

Answer

The directory has ACLs preventing access

Question 10

A Red Hat Enterprise Linux 8 system was recently updated via 'yum update'. After reboot, the systemd-logind service fails to start with the error 'Failed to start Login Service' and 'Permission denied' messages in the journal. The administrator checks the SELinux status with 'getenforce' and it returns 'Enforcing'. The administrator also notices that the '/var/run' directory is now a symlink to '/run'. There are no firewall issues. The service works if SELinux is set to permissive. Which single action should the administrator take to resolve this issue permanently?

Accepted Answer

Run 'restorecon -Rv /run' to restore default SELinux contexts for /run. After a yum update, SELinux contexts on /run may be incorrect because /var/run is a symlink to /run. When SELinux is enforcing, systemd-logind requires the correct context (typically system_u:object_r:var_run_t:s0) on /run to access its runtime files. Running 'restorecon -Rv /run' restores the default SELinux contexts for all files under /run, resolving the 'Permission denied' errors permanently without disabling SELinux.

Answer

Add 'selinux=0' to kernel boot parameters and reboot

Answer

Edit the systemd-logind service unit to add 'Permissions=yes'

Answer

Reinstall the systemd-logind package using 'yum reinstall systemd'

Question 11

A server has a requirement that all users in the 'finance' group must have a password aging policy that forces password change every 90 days. Which approach best achieves this for existing users?

Accepted Answer

Write a script to run 'chage -M 90' for each user in the finance group. `chage -M 90` sets the maximum password age for a specific user, and by scripting it to apply to all members of the 'finance' group, you directly enforce the 90-day policy on existing users. This approach works regardless of the default settings in `/etc/login.defs`, which only affect new users, and avoids the manual and error-prone editing of `/etc/shadow`.

Answer

Set PASS_MAX_DAYS 90 in /etc/login.defs

Answer

Edit /etc/shadow and change the fifth field for all users

Answer

Configure pam_pwquality.so to enforce password age

Question 12

An administrator attempts to mount an XFS filesystem from /dev/sdc1 to /mnt/archive but receives the error: 'mount: /mnt/archive: wrong fs type, bad option, bad superblock on /dev/sdc1, missing codepage or helper program, or other error.' The output of 'dumpe2fs /dev/sdc1' shows 'dumpe2fs: Bad magic number in super-block while trying to open /dev/sdc1'. What is the most likely problem?

Accepted Answer

The filesystem on /dev/sdc1 is XFS, not ext4. The error message 'wrong fs type' combined with 'dumpe2fs: Bad magic number in super-block' indicates that the filesystem on /dev/sdc1 is not an ext2/3/4 filesystem. dumpe2fs is designed to read ext2/3/4 superblocks, and the 'bad magic number' error means it cannot find a valid ext superblock. Since the administrator is trying to mount an XFS filesystem, the correct tool to examine it is xfs_db or xfs_info, not dumpe2fs. Therefore, the most likely problem is that the filesystem is XFS, not ext4.

Answer

The mount point /mnt/archive does not exist

Answer

The XFS kernel module is not loaded

Answer

The partition /dev/sdc1 does not exist

Question 13

A system administrator notices that a server is responding slowly. The administrator runs `top` and sees a process named `backup_script` consuming 95% CPU. The process runs as root and is supposed to run nightly backups. However, the system load average is low. The administrator wants to investigate without killing the process. Which of the following is the best course of action?

Accepted Answer

Use `renice -n 19 -p ` to lower the priority of the process.. `renice -n 19 -p ` lowers the CPU scheduling priority of the running `backup_script` process to the lowest possible value (19), which reduces its CPU consumption without killing it. This allows the administrator to investigate the cause of the high CPU usage while minimizing the impact on other processes and system responsiveness.

Answer

Use `nice -n 19 ./backup_script` to start the process with lower priority next time.

Answer

Use `chrt -i 0 <PID>` to set the scheduling policy to idle.

Answer

Use `kill -STOP <PID>` to pause the process and then resume later.

Question 14

An administrator notices that the /tmp directory is filling up quickly. They want to find all files in /tmp that are larger than 100 MB and owned by user 'ftp', then delete them. The administrator runs: find /tmp -type f -size 100M -user ftp -exec rm {} \;. However, this command deletes only files that are exactly 100 MB, not larger. Which find expression should be used instead?

Accepted Answer

find /tmp -type f -size +100M -user ftp -exec rm {} \;. The `find` command uses `+` before a size value to match files larger than that size, not exactly equal. The original command omitted the `+`, so it matched only files exactly 100 MB. Adding `+100M` correctly selects files larger than 100 MB.

Answer

find /tmp -type f -size 100M -user ftp -exec rm {} \;

Answer

find /tmp -type f -size +100M ! -size 100M -user ftp -exec rm {} \;

Answer

find /tmp -type f -size +100M -size -100M -user ftp -exec rm {} \;

Question 15

A server's firewall is managed by firewalld. The admin adds a rule to allow HTTPS traffic to the public zone, but clients still cannot connect. What is the most likely cause?

Accepted Answer

The rule was added with --permanent but firewall-cmd --reload was not run.. When a rule is added with the `--permanent` flag in firewalld, it is written to the configuration files but not applied to the runtime firewall. Until `firewall-cmd --reload` is executed, the runtime configuration remains unchanged, so the new rule allowing HTTPS traffic is not active. Clients cannot connect because the firewall is still blocking HTTPS based on the old runtime rules.

Answer

The rule must be added as a rich rule, not a simple service.

Answer

The default zone is not set to public.

Answer

firewalld is just a wrapper for iptables, so iptables rules must be cleared.