add CLAUDE.md for Claude Code guidance

CLAUDE.md

+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Overview
+
+etersoft-admin-essential is a collection of 340+ system administration scripts for Etersoft's ALT Linux infrastructure. It covers server provisioning, hosting platform operations (Azbyka project), storage management, and monitoring automation.
+
+## Repository Structure
+
+**Core Domains:**
+- `vz/` - OpenVZ container management (cloning, migration, task-based creation)
+- `vz/azbyka/` - Azbyka hosting automation (50+ scripts for nginx, migrations, task-based VM creation)
+- `web/` - Site management, user/FTP management, nginx statistics
+- `gluster/` - GlusterFS repair and recovery tools
+- `hdd/` - RAID, SSD failure handling, LVM caching, disk diagnostics
+- `mail/` - Mail queue management, account archival, spam handling
+- `router/` - Network failover, traffic monitoring
+- `dns/` - Domain management via NetBreeze/NIC
+
+**System Management:**
+- `ansible/playbooks/` - Ansible playbooks for desktop upgrades, system setup, package management
+- `etersoft/` - System/user configuration (`tune_new_system.sh`, `tune_new_user.sh`)
+- `etersoft-cron/` - Scheduled tasks (updates, rsync, log rotation)
+- `fail2ban/` - Custom filters and rule checking
+- `backup/` - Database backup, archive management
+
+**Other:**
+- `users/` - User management scripts
+- `ddos/` - DDoS mitigation
+- `dc/`, `dc-client/` - Domain controller scripts
+- `nginx/` - URL statistics and error analysis (Python + Shell)
+
+## Technology Stack
+
+- **Shell/Bash** - Primary scripting language
+- **Python** - Data processing and statistics
+- **Ansible** - System automation playbooks
+- **OpenVZ** - Virtualization (legacy containers)
+- **GlusterFS** - Distributed storage
+- **Nginx/Apache** - Web serving
+
+## Common Patterns
+
+- Modular functions in `common/`, `vz/azbyka/functions`, `web/functions`
+- Task-based configs (`.task` files) for automation
+- Error handling via `fatal()`, `assure()` functions
+- SSH automation for remote execution across hosts
+- girar integration for ALT Linux task tracking
+
+## Ansible
+
+Playbooks are in `ansible/playbooks/`. Inventory is typically linked from `/root/.ansible/`.
+
+```bash
+ansible-playbook -i /root/.ansible/hosts ansible/playbooks/NAME.yml
+```