Linux+ is a doing exam
CompTIA Linux+ XK0-006 is 90 questions in 90 minutes, with 720 to pass on the 100 to 900 scale. It expects roughly a year of hands-on Linux server experience and assumes A+, Network+ or Server+ level knowledge. If you only read about commands, the performance-based items will find you out.
The domains are system management (23%), services and user management (20%), security (18%), automation, orchestration and scripting (17%), and troubleshooting (22%). System management and troubleshooting together are almost half the exam, and security shows up inside every other domain.
Build one small server you can break
You do not need a rack. A local virtual machine or a cloud free tier is enough, and our browser labs cover the reasoning when you cannot install one. Build a server with:
- two users, one sudoer and one ordinary account;
- a mounted data volume and an entry in /etc/fstab;
- a static network configuration and a working DNS resolver;
- sshd on a non-default port with key-only login;
- a firewall that allows SSH and one web port;
- a systemd service you wrote yourself;
- a cron job and a systemd timer that do the same task;
- a small Bash script with a function and an error check.
Then break each item and repair it. That list is most of the exam in miniature.
Eight weeks at a steady pace
- Week 1: files, permissions and text. Navigation, find, grep, sed, awk, redirection, pipes, hard and soft links, ownership, mode bits, umask, ACLs. Practice reading a permission string until 640 and 2750 mean something instantly.
- Week 2: storage and boot. Partitioning, filesystems, mount units, fstab, LVM, swap, GRUB, initramfs, boot targets. Know the difference between a mount that survives reboot and one that does not.
- Week 3: services and users. systemd units, enable and start, journalctl, useradd and usermod, groups, sudoers, PAM basics, SSH configuration. Read unit status output and name the failing dependency.
- Week 4: networking and name resolution. ip, ss, nmcli, resolv.conf, systemd-resolved, firewalld zones, nftables concepts, time sync. Test from the host, not just from memory.
- Week 5: security. SSH hardening, sudo policy, file permissions, SELinux contexts and booleans, audit basics, package signing, vulnerability response. Read an SELinux denial and explain which context is wrong.
- Week 6: scripting and automation. Bash variables, conditionals, loops, functions, exit codes, strict mode, cron, systemd timers, Git basics, Ansible concepts. Write a script that fails loudly instead of silently.
- Week 7: containers and cloud. Images, containers, volumes, networks, registries, a simple Dockerfile, Kubernetes vocabulary, cloud instance concepts. Know what runs on the host and what runs in the container.
- Week 8: troubleshooting and timed sets. Two mixed sets and a repair week. Work the symptoms: boot failure, full disk, service down, DNS failure, permission denied, SELinux denial, container cannot reach the network.
A command routine that sticks
Do not memorise flags in alphabetical order. Learn each command by the question it answers:
- "What is using this port?" ss -lntp
- "What changed in the service?" systemctl status and journalctl -u
- "Why can this user not read the file?" namei -l, getfacl, ls -lZ
- "What is filling the disk?" df -h, du -xhd1, lsof +L1
- "What is this process doing?" ps, top, strace, /proc
- "Why did the boot fail?" systemctl --failed, journalctl -b, dmesg
Say the question out loud before you type. The exam asks the question, not the flag.
Security is not a separate week
SELinux, firewalls, SSH hardening and sudo policy are operational habits. When you build the server in week 1, harden it as you go. When you write a script in week 6, handle secrets correctly. When you troubleshoot in week 8, check the security layer before you disable it. "Turn off SELinux" is almost never the right exam answer.
Practise with labs and PBQs
The command line is the course, so the labs are the syllabus. The XK0-006 pack holds 8 performance-based questions and 90 labs, all run in a Linux console and graded on the end state of the machine (counts from the live catalogue).
Follow the week order. Weeks 1 and 2 take the file, permission and storage tasks, where a mode bit or an fstab entry is either right or the box does not boot. Weeks 3 and 4 take services, users and networking, and those are the tasks where reading unit status is worth more than typing. Week 5 takes the SELinux and hardening tasks, which is also how you learn that a denial has a cause. Weeks 6 and 7 take scripting, containers and cloud. Week 8 is break-and-repair only.
There is a reason to practise in a browser rather than only on your own VM: a graded task tells you whether the state is right, while a VM tells you whether the service happens to work. The Linux+ lab catalogue lists each task with its objective, and the labs hub covers the container and cloud tasks if you are also studying for a cloud certificate.
If you are choosing between console-heavy certifications, the CCNA lab comparison is worth reading first: it explains what each platform grades, which is the same question you should ask of a Linux lab before you rely on it.
Book when you can repair without a guide
Book when you can take a broken service, a full disk or a denied login and work it to a root cause without following a tutorial. Repeats feel good; fresh breakage is the honest test. The app's labs reset and change, which is the point.