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Where to start First steps track · 15 stages →

Tracks 13

First steps 15 stages Users, permissions, and processes 13 stages Packages, services, and logs 13 stages Networking 15 stages Storage 12 stages Bash: text processing and scripts 9 stages Inside the system: resources, kernel, processes 13 stages Web stack 9 stages Server security 10 stages Containers: Docker and compose 11 stages Automation: Git and Ansible 8 stages Observability: metrics, alerts, logs 9 stages SRE practices: SLOs, incidents, redundancy 8 stages All tracks · 13 →

Labs 93

Easy 17 Medium 67 Hard 9

Topics

First steps 7 Users, permissions, and processes 6 Packages, services, and logs 7 Networking 9 Storage 9 Bash: text processing and scripts 4 Inside the system: resources, kernel, processes 8 Web stack 7 Server security 7 Containers: Docker and compose 5 Automation: Git and Ansible 4 Observability: metrics, alerts, logs 6 SRE practices: SLOs, incidents, redundancy 5 On two machines 14 All labs · 93 →

Wiki 191

Basic commands bash, cd, man Files and directories touch, basename, find Text and search grep, sed, cat Users and permissions ls, chmod, id Processes ps, vmstat, jobs Services and systemd systemctl, crontab, pg_lsclusters Network ping, ip, ss Storage and file systems df, lsblk, pvs Logs and audit journalctl, tail, cat Boot update-grub, uname, sysctl Packages apt, snap Security sudo, sshd, ufw Automation ansible, ansible-playbook Containers systemctl, docker, docker-compose Observability systemctl, ss, amtool SRE awk, curl, cd Command index a–z All of the wiki · 191 →

Tools 14

Security

Password generator MD5, SHA and htpasswd JWT decoder

Data formats

JSON validator YAML ⇄ JSON UUID generator

Text

Character counter Compare texts

Linux and network

chmod permissions cron explained IPv4 subnets

Encoding and conversion

Base64 and URL Unix time Data size units All tools · 14 →

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Tracks

Where to start · 1.1

First steps

15 stages · 8 labs

Start the track

13 tracks · 145 stages

1 · Foundations

First steps 15 stages

2 · The system

Users, permissions, and processes 13 stages
Packages, services, and logs 13 stages

3 · Admin craft

Networking 15 stages
Storage 12 stages
Bash: text processing and scripts 9 stages

4 · Server in production

Inside the system: resources, kernel, processes 13 stages
Web stack 9 stages
Server security 10 stages
Containers: Docker and compose 11 stages
Automation: Git and Ansible 8 stages
Observability: metrics, alerts, logs 9 stages

5 · Operations

SRE practices: SLOs, incidents, redundancy 8 stages

Phase 1 · Foundations

The terminal, files, text and pipelines.

1.1 First steps From system basics and command input to navigation, files, text, and pipelines. 15 stages · 8 labs

Phase 2 · The system

Users and permissions, processes, services and logs.

2.1 Users, permissions, and processes From file permissions and accounts to sudo, groups and processes. 13 stages · 6 labs
2.2 Packages, services, and logs From packages and systemd services to your own unit, the journal, schedules and log rotation. 13 stages · 7 labs

Phase 3 · Admin craft

Disks, networking and Bash scripts.

3.1 Networking From addresses and routes to ports, filtering, DNS, SSH, multi-host connectivity and packets in tcpdump. 15 stages · 9 labs · two machines
3.2 Storage From space diagnosis and mounting, through preparing a new disk and a RAID 1 mirror, to logical volumes and data recovery. 12 stages · 9 labs
3.3 Bash: text processing and scripts Searching and editing text with grep, sed and awk, your own scripts with arguments and checks, exit codes and scheduled runs with a log and a lock. 9 stages · 5 labs

Phase 4 · Server in production

Resources and the kernel, the web stack, security, containers, automation and observability.

4.1 Inside the system: resources, kernel, processes Load average and the CPU, memory and the OOM killer, process limits and kernel parameters, disk load, strace and /proc, kernel messages, the system boot and emergency mode, time synchronisation — up to triaging a slow server. 13 stages · 9 labs · two machines
4.2 Web stack Sites and reverse proxy on nginx, certificates and HTTPS, PostgreSQL access and restoring from a dump — up to a site and a database on two machines. 9 stages · 8 labs · two machines
4.3 Server security What a server exposes and what it keeps running after an update, password policy and fail2ban, a service with least privilege, AppArmor and auditd — up to getting a new server ready for publication. 10 stages · 8 labs · two machines
4.4 Containers: Docker and compose Image and container, ports, environment and restart, your own Dockerfile, volumes, container networking and a compose stack, memory limits and the user inside a container. 11 stages · 6 labs
4.5 Automation: Git and Ansible Configuration under git: who changed what, how to get the working version back and update a server from a repository; Ansible: inventory, ad-hoc commands, an idempotent playbook, roles, variable precedence and secrets in a vault — up to configuring a second machine from the first. 8 stages · 5 labs · two machines
4.6 Observability: metrics, alerts, logs Machine and application metrics in Prometheus and PromQL queries; alert rules and notification delivery through Alertmanager; logs from several machines on one collector and investigating with logs — up to watching a second machine from the first. 9 stages · 7 labs · two machines

Phase 5 · Operations

SLOs, incidents and redundancy.

5.1 SRE practices: SLOs, incidents, redundancy Availability and latency from a log, SLOs and error budgets; the first minutes of an incident by a runbook, rolling back a release and a blameless postmortem; a load balancer with health checks and a keepalived floating address — up to an on-call shift on two machines. 8 stages · 6 labs · two machines

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Labs

Difficulty

Easy 17
Medium 67
Hard 9

Topics

First steps7
Users, permissions, and processes6
Packages, services, and logs7
Networking9
Storage9
Bash: text processing and scripts4
Inside the system: resources, kernel, processes8
Web stack7
Server security7
Containers: Docker and compose5
Automation: Git and Ansible4
Observability: metrics, alerts, logs6
SRE practices: SLOs, incidents, redundancy5
On two machines14

New labs

A mirror on one disk Storage 25 min
The role does not apply Automation: Git and Ansible 30 min
The machine after a reboot Inside the system: resources, kernel, processes 20 min

All labs · 93 → ←→ sections · ↑↓ links · Esc to close

Wiki

Sections 191 articles

Basic commands bash, cd, man
Files and directories touch, basename, find
Text and search grep, sed, cat
Users and permissions ls, chmod, id
Processes ps, vmstat, jobs
Services and systemd systemctl, crontab, pg_lsclusters
Network ping, ip, ss
Storage and file systems df, lsblk, pvs
Logs and audit journalctl, tail, cat
Boot update-grub, uname, sysctl
Packages apt, snap
Security sudo, sshd, ufw
Automation ansible, ansible-playbook
Containers systemctl, docker, docker-compose
Observability systemctl, ss, amtool
SRE awk, curl, cd

Command index 437

a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
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Glossary309
Printable cheat sheets191

All articles · 191 → ←→ sections · ↑↓ links · Esc to close

Tools

Popular

Password generator
YAML ⇄ JSON
UUID generator
Character counter

Security

Password generator
MD5, SHA and htpasswd
JWT decoder

Data formats

JSON validator
YAML ⇄ JSON
UUID generator

Text

Character counter
Compare texts

Linux and network

chmod permissions
cron explained
IPv4 subnets

Encoding and conversion

Base64 and URL
Unix time
Data size units

All tools · 14 → ←→ sections · ↑↓ links · Esc to close

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Wiki/Glossary

array rebuild

Storage and file systems

Copying data onto a new RAID disk after the failed one is replaced; /proc/mdstat shows recovery = N%. While it runs, the array stays degraded.

In depth in the articles

In depth in the articles

RAID: mirrors, parity and degraded arrays — the full analysis

Related terms

hot spare
degraded array

Password generator
JSON validator
YAML ⇄ JSON
Character counter
chmod permissions
cron explained

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