Study Hub / CompTIA Linux+ (XK0-006) / Domain 1.0
CompTIA Linux+ (XK0-006) Domain 1.0: System Management — Explained
Domain 1.0 is the largest Linux+ domain: the fundamentals of keeping Linux systems running — how they boot, how the kernel talks to hardware, how storage is organized, how networking is configured, and how data is protected.
Boot process: from power to prompt
- The sequence — firmware (UEFI/BIOS) → bootloader (GRUB2) → kernel loads →
init(systemd, PID 1) → targets reached. Know the order: "won't boot" diagnosis starts by asking how far it got. - GRUB2 — the bootloader: picks the kernel, passes parameters, offers the boot menu. A broken GRUB config = a system that can't start its kernel — fixable from rescue media.
- systemd targets — the modern "runlevels":
multi-user.target(text/console),graphical.target(GUI).systemctl get-default/set-defaultcontrols the boot target. - Kernel modules — drivers loaded on demand:
lsmod(what's loaded),modprobe(load/remove),/etc/modprobe.d/(persistent config). Missing module = hardware the kernel can't see.
Storage: partitions, LVM, and filesystems
- Partitioning — GPT (modern, UEFI, huge disks) vs. MBR/msdos (legacy, 2 TB limit). Partitions are carved with
fdisk/gdisk/parted. - LVM — the flexible layer: physical volumes → volume groups → logical volumes. Resize filesystems without repartitioning; take snapshots for backups. "We need more space on /var" is an LVM afternoon, not a reinstall.
- RAID — RAID 0 (striping: speed, no redundancy), RAID 1 (mirroring: redundancy), RAID 5 (striping + parity: one disk may fail), RAID 6 (two may fail), RAID 10 (mirror of stripes: performance + redundancy). RAID is uptime, not backup.
- Filesystems — ext4 (the default workhorse), XFS (large files/high performance), Btrfs (snapshots, pooling).
mount/umount, and/etc/fstabfor persistence — a bad fstab entry can halt a boot, so keep a known-good backup.
Networking, packages, and backups
- Network configuration — interfaces (
ip addr), routes (ip route), DNS (/etc/resolv.conf, systemd-resolved), hostnames.ipreplacedifconfig/route— know the modern commands. - Connectivity ladder — link (cable/interface up?) → address (correct IP/subnet?) → gateway (route?) → DNS (resolves?) → remote (port open? firewall?). Diagnose bottom-up, every time.
- Package management —
apt/dpkg(Debian/Ubuntu),dnf/rpm(RHEL/Fedora),zypper(SUSE). Repositories provide signed packages; update caches before installing; know which family a distro belongs to. - Backups —
tar(archives),rsync(efficient syncs — the workhorse),dd(bit-for-bit — powerful and dangerous). The 3-2-1 rule: 3 copies, 2 media types, 1 offsite. An untested backup is a rumor. - Virtualization basics — hypervisors (KVM on Linux), VMs vs. containers (full OS vs. shared kernel). Know where your workload actually runs.
The must-memorize table: RAID levels
What each level survives.
| RAID | Method | Disk failures survived | Use case |
|---|---|---|---|
| RAID 0 | Striping | Zero — one fails, all data lost | Speed only, never alone for data |
| RAID 1 | Mirroring | One (per mirror) | Simple redundancy, 50% capacity cost |
| RAID 5 | Striping + parity | One | Good balance, minimum 3 disks |
| RAID 6 | Striping + double parity | Two | Large arrays where rebuilds are slow |
| RAID 10 | Mirror of stripes | One per mirror pair | Performance + redundancy |
Try it: 4 sample questions
Sample questions to check your understanding of this domain. Answers and full reasoning are tucked under each one.
1. A server needs more space on its /var logical volume without downtime or repartitioning. Which technology makes this possible, and roughly how?
- A. A. RAID 0 — stripe more disks
- B. B. LVM — extend the logical volume (and grow the filesystem) from free space in the volume group
- C. C. A bigger /etc/fstab
- D. D. Reinstall with larger partitions
Show answer & reasoning
B. LVM decouples filesystems from physical partitions: lvextend grows the logical volume from VG free space, then the filesystem grows into it — online, no repartitioning. That's LVM's core value proposition. RAID (A) is about disk redundancy, not flexible volumes.
2. A system stops during boot with errors about an unmountable filesystem listed in fstab. What likely happened, and what's the recovery path?
- A. A. The kernel is corrupted — reinstall
- B. B. A bad fstab entry (typo, removed disk) halts the boot — fix from rescue/emergency mode or a live environment
- C. C. GRUB is fine so nothing is wrong
- D. D. The CPU failed
Show answer & reasoning
B. systemd tries to mount everything in fstab at boot; a bad entry (wrong UUID, disk removed) blocks the boot. Recovery: emergency shell or live media, fix the entry, reboot. This is why you keep fstab backups and use nofail for non-critical mounts. The kernel (A) loaded fine — it got past GRUB.
3. A database needs to survive a single disk failure with good read performance and minimum 3 disks. Which RAID level, and what is its limitation?
- A. A. RAID 0
- B. B. RAID 5 — striping with parity survives one disk failure; limitation: rebuilds are slow and a second failure during rebuild is fatal
- C. C. RAID 1
- D. D. No RAID — backups are enough
Show answer & reasoning
B. RAID 5's parity survives exactly one failure with good capacity efficiency (minimum 3 disks). The honest limitation: on large modern disks, rebuilds take so long that a second failure during rebuild kills the array — which is why RAID 6 exists for big arrays. RAID is uptime; backups are recovery — you need both (D confuses the two).
4. A technician must copy only changed files from /data to a backup server efficiently over SSH, preserving permissions. Which tool and why?
- A. A. tar — simplest archive
- B. B. rsync — transfers only deltas, preserves permissions/ownership, works over SSH
- C. C. dd — bit-for-bit copy
- D. D. cp -r
Show answer & reasoning
B. rsync's delta-transfer sends only changed blocks (fast incremental backups), -a preserves permissions/ownership/timestamps, and it tunnels over SSH natively. tar (A) re-copies everything; dd (C) copies whole devices bit-for-bit (wrong granularity, dangerous); cp (D) has no delta or remote logic.
This was one domain. The simulator drills all 5.
This free preview covered System Management (Domain 1.0, 23%). Not covered here: Security (Domain 3.0, 18%); Troubleshooting (Domain 5.0, 22%). Linux security hardening and scenario troubleshooting stay in the paid guide and practice bank. The ByteBar Practice Exam Simulator drills every domain with 1,000 exam-style questions — $9.99 one-time unlocks all 28 exams. Prefer to read? The full Linux+ Study Guide is in the ByteBar shop on Etsy.
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