linux-kernel-systemd-internals
Provides patterns for Linux kernel architecture, the systemd init subsystem, and advanced server administration based on systemd for Linux SysAdmins (David Both) and Understanding Linux Kernel Development. Covers unit management (.service, .socket, .timer, .mount), cgroups v2, journald, namespaces, kernel networking (Netfilter, eBPF, sockets), and sysctl performance tuning.
Source facts
- Repository
- dandgabr/Coacus
- Last source activity
- September 20, 2026 at 03:33
- Detected SKILL.md language
- English
- Stars
- 0
- Forks
- 0
Install options
The review-first prompt is selected by default. You can switch to a direct command or download a local copy.
Review the source files
Read SKILL.md and any companion files shown by SkillsMP before deciding whether to install.
File Explorer
5 filesShowing SKILL.md
SKILL.md
Source instructions · Read-only preview- name
- linux-kernel-systemd-internals
- description
- Provides patterns for Linux kernel architecture, the systemd init subsystem, and advanced server administration based on systemd for Linux SysAdmins (David Both) and Understanding Linux Kernel Development. Covers unit management (.service, .socket, .timer, .mount), cgroups v2, journald, namespaces, kernel networking (Netfilter, eBPF, sockets), and sysctl performance tuning.
# Linux Kernel, systemd, and Advanced System Administration
This skill establishes the standards and practices for Linux operating-system engineering, service management through **systemd**, resource control with **cgroups v2**, and network/kernel tuning documented by **David Both**, **Lincoln Boucher**, and **Christian Benvenuti**.
---
## 🐧 1. systemd Architecture and Unit Types
```
┌─────────────────────────────────────────────────────────────┐
│ systemd (PID 1) │
├──────────────┬──────────────┬──────────────┬────────────────┤
│ .service │ .socket │ .timer │ .mount │
│ (Daemons e │ (Ativação │ (Agendamento │ (Pontos de │
│ Processos) │ por Rede) │ preciso) │ Montagem) │
└──────────────┴──────────────┴──────────────┴────────────────┘
```
### Anatomy of a Secure Service (`/etc/systemd/system/myapp.service`)
```ini
[Unit]
Description=Plataforma de Microsserviço de Alta Disponibilidade
After=network.target postgresql.service
Requires=postgresql.service
[Service]
Type=notify
ExecStart=/usr/local/bin/myapp --config /etc/myapp/config.yaml
ExecReload=/bin/kill -HUP $MAINPID
Restart=on-failure
RestartSec=5s
# Hardening e Isolamento de Segurança
User=appuser
Group=appgroup
NoNewPrivileges=true
ProtectSystem=strict
ProtectHome=true
PrivateTmp=true
PrivateDevices=true
ProtectKernelModules=true
ProtectKernelTunables=true
ProtectControlGroups=true
RestrictRealtime=true
MemoryMax=2G
CPUQuota=200%
[Install]
WantedBy=multi-user.target
```
---
## ⚙️ 2. Kernel Performance Tuning (`/etc/sysctl.d/99-custom.conf`)
| Sysctl Parameter | Recommended Value | Purpose |
| :--- | :--- | :--- |
| `net.core.somaxconn` | `65535` | Increases the size of the pending-connection queue for the TCP listener. |
| `net.ipv4.tcp_max_syn_backlog` | `65535` | Protects against traffic spikes and SYN floods. |
| `net.ipv4.ip_local_port_range` | `1024 65535` | Expands the ephemeral port range for outbound connections. |
| `vm.swappiness` | `10` | Avoids aggressive swap use, preserving RAM for cache. |
| `fs.file-max` | `2097152` | Global limit of open file descriptors. |
View on GitHub