CompTIA Linux+ (XK0-006) Practice Exam

Correct: A — update /etc/resolv.conf. That file lists the DNS resolvers the system uses. After a migration, a stale nameserver entry there is the immediate cause of failed internal resolution, so it is the first thing to check (or the resolver config managing it, such as systemd-resolved or NetworkManager).

Why not the others: a new kernel (B), new RAM (C), and a desktop background (D) have nothing to do with name resolution.

Correct: A — use chmod to restore execute permission. “Permission denied” on a previously working script almost always means the execute bit was lost; chmod +x script.sh restores it.

Why not the others: new hardware (B), a filesystem upgrade (C), and rebooting a switch (D) are unrelated to a file’s permission bits.

Correct: A — sshd is not running. A successful ping proves network-layer reachability, so the problem is above that layer. If the SSH daemon is stopped (or its port is firewalled), connections fail even though ping works.

Why not the others: a faulty cable (B) would break the ping too; insufficient disk space (C) and an expired password (D) produce different, specific errors rather than a refused/timed-out connection.

Correct: A — cron. cron schedules commands to run automatically at set times, which is exactly what a recurring daily backup needs (a systemd timer would also serve).

Why not the others: vi (B) is a text editor; df (C) reports filesystem disk usage; top (D) shows running processes. None of them schedules a task.

Correct: A — archive, rotate, or remove old logs. /var/log fills with accumulated log data; clearing or rotating it (ideally configuring logrotate) reclaims space and prevents a full filesystem from destabilizing services.

Why not the others: CPU (B) and RAM (C) are unrelated to disk space; disabling SELinux (D) weakens security and does not free disk.

Correct: A — run apachectl configtest. Since the failure followed a config change, testing the configuration syntax pinpoints the error before you restart the service — the logical, low-risk first move (also checkable via the service’s journal logs).

Why not the others: a BIOS update (B) is unrelated to a web service; reformatting (C) is catastrophic overkill; editing /etc/fstab (D) concerns mounting filesystems, not Apache.

Correct: A — stop writing and recover immediately. A deleted file’s data blocks remain on disk until overwritten. Minimizing further writes (ideally remounting read-only or working from another system) preserves the best chance for a recovery tool to retrieve it.

Why not the others: reinstalling the OS (B) writes heavily over the disk; a kernel upgrade (C) is irrelevant; a background change (D) does nothing for recovery.

Correct: A — chmod 700. The octal digits are owner/group/other. 7 = read+write+execute for the owner, and 0/0 means no permission for group and others — exactly “owner can execute, nobody else has access.”

Why not the others: 444 (B) is read-only for everyone with no execute; 777 (C) grants full access to everyone; 666 (D) is read+write for all with no execute. None matches the owner-only-execute requirement.

Correct: A — firewall rules limiting port 22 to trusted IPs. A host firewall (nftables, iptables, or UFW) is the standard control for restricting which source addresses may reach the SSH service, and pairs well with key-based auth for defense in depth.

Why not the others: a GUI (B), more swap (C), and a different shell (D) do nothing to control which remote hosts can connect.

Correct: A — find /home -name config.txt. find searches a directory tree recursively and matches by name, returning every config.txt beneath /home regardless of depth.

Why not the others: ls -l (B) only lists one given path and does not recurse for a name; cat (C) prints file contents; df -h (D) reports disk usage. None performs a recursive name search.