Core Code
Core Code Modern Dev Handbook
LINUX-PRODUCTION Contents
Linux Fundamentals for Production
Filesystem Layout (FHS) in Practice Users, Groups, and Service Accounts Permissions & ACLs (chmod/chown/setuid) Sudoers Safe Defaults Packages: apt/dnf, Repos, and Pinning Shell & Environment Hygiene Editing Configs Safely Time, Timezones, and NTP System Introspection Toolkit
Processes & Signals
Linux Process Model (PID, PPID, Fork/Exec) ps/top/htop: Finding What Hurts Signals in Practice (TERM/KILL/HUP) nice/renice and Scheduling Basics ulimits and Resource Limits Background Jobs (nohup, tmux, systemd-run) /proc and What It Tells You cgroups Basics (CPU/Memory Isolation) Zombies, Orphans, and Stuck Processes
systemd & Services
systemd Unit Types Overview Service Unit Best Practices Dependencies & Ordering (After/Wants/Requires) Restart Policies and Backoff Environment Files and Secrets Handling journald Basics (Reading, Filtering, Retention) Logging Practices with systemd Timers vs Cron Debugging systemd Services
Networking Basics for Production
ip, routes, and interfaces DNS Debugging (dig, resolvectl, hosts) Ports and Sockets with ss curl for HTTP Debugging TCP Basics (Handshake, States, Retries) Firewall Overview (nftables/iptables/ufw) NAT and Port Forwarding Concepts TLS and Certificates Basics Network Troubleshooting Playbook
Storage & Filesystems
Disk Layout and Partitioning (lsblk/fdisk) Filesystems (ext4/xfs) Basics Mounts and /etc/fstab Safety Disk Usage: df vs du (and Why They Differ) Inodes and “Disk Full” Mysteries Swap Strategy in Production Log Rotation (logrotate) Basics Temporary and Runtime Storage Hygiene Backup Storage Considerations
Security Basics
SSH Hardening in Production Users and Least Privilege in Production Firewall Minimum Rules for Production Linux Patching Strategy in Production Managing Secrets on Linux Hosts Linux Audit and Basic Logging in Production Fail2ban and Rate Limiting in Production SELinux and AppArmor Overview in Production Linux Security Baseline Checklist for Production
Observability on Linux
Linux Log Sources Map in Production journalctl Power Usage in Production Log Structure and Correlation in Production Metrics Hooks Overview in Production Health Checks and Readiness in Production Tracing Mindset for Linux and Production Systems Core Dumps Basics in Production Debug Packages and Symbols in Production Linux Observability Checklist for Production
Performance & Debugging
Load Average Explained for Production Debugging CPU Profiling Basics in Linux Production Memory Pressure Basics in Linux Production IO Bottlenecks and iostat in Production lsof and Open Files in Production Debugging Practical strace Usage in Production Sockets Debugging Tools in Linux Production dmesg and Kernel Signals for Production Debugging Production Debugging Workflow for Linux Systems
Deployment Patterns
Environment and Configuration Management in Production Release Directory Pattern for Safe Linux Deployments Zero-Downtime Restarts in Production Running Migrations Safely in Production Secrets Deploy Patterns in Production Backups and Restore Drills in Production Rollback Strategies for Production Deployments Maintenance Windows in Production Operations Production Deployment Checklist for Linux Systems
Production Checklists
Writing Effective Runbooks for Production Systems Failure Modes Mapping for Linux Production Systems Incident Response Basics for Linux Production Break-Glass Access in Production Capacity Planning Basics for Linux Production Systems Monitoring and Alerting Baseline for Linux Production Production Readiness Review for Linux Systems Configuration Drift in Linux Production Systems Go-Live Checklist

Sudoers Safe Defaults

Grant the minimum commands with audit-friendly sudo rules and avoid footguns.
On this page

Why Sudo Design Matters in Production

Sudo is not just a convenience tool. It is a controlled privilege escalation mechanism. Improper sudo configuration turns your server into a shared root shell. Production systems must treat sudo rules as security policy, not shortcuts.

Never Edit /etc/sudoers Directly

Always use: 

visudo

Better practice: 

/etc/sudoers.d/

Create separate policy files: 

/etc/sudoers.d/deploy
/etc/sudoers.d/ops

Principle of Least Privilege

Instead of giving full root access: 

alice ALL=(ALL) ALL

Restrict commands: 

alice ALL=(ALL) NOPASSWD: /bin/systemctl restart myapp

Now Alice cannot run arbitrary commands as root.

Command Whitelisting Strategy

Allow only the exact binary paths. Avoid wildcards like: 

/usr/bin/*

That defeats the purpose of restriction.

Deploy User Pattern

Production-safe deployment model:

  • deploy user owns release directory
  • deploy can restart service
  • deploy cannot modify system configuration
deploy ALL=(root) NOPASSWD: /bin/systemctl restart myapp

Password vs NOPASSWD

NOPASSWD increases automation simplicity but reduces friction barriers. Use it only for narrowly scoped commands. For interactive maintenance, require password confirmation.

Auditing Sudo Usage

Check logs: 

journalctl -u sudo
grep sudo /var/log/auth.log

Every sudo execution should be traceable.

Common Production Mistakes

  • Giving full sudo to developers “temporarily”
  • Using ALL=(ALL) ALL everywhere
  • Not logging sudo usage
  • Allowing shell escape commands

Shell Escape Risk

Some programs allow shell escape: 

sudo vim
:shell

This can lead to unrestricted root access. Be careful which commands you whitelist.

Mental Model

Sudo rules define your privilege boundaries. If a service or user is compromised, proper sudo restrictions prevent full system takeover.

Production Checklist

  • Use sudoers.d instead of editing main file
  • No broad ALL=(ALL) ALL entries
  • Whitelist exact commands
  • Audit logs enabled
  • Deploy user cannot open root shell
Packages: apt/dnf, Repos, and Pinning →