platform-deployments/provisioning/set-hostname.sh

#!/bin/bash
# set-hostname.sh - OS-aware hostname configuration
# Sets hostname using the appropriate method for the target OS
#
# Usage: ./set-hostname.sh <short-hostname> <fqdn> [hostname-method]
#
# Arguments:
#   short-hostname  - Short hostname (e.g., "apricot", "0")
#   fqdn            - Fully qualified domain name (e.g., "apricot.voyager.nasty.sh")
#   hostname-method - Optional: hostnamectl-only, etc-hostname, cloud-init
#                     If not provided, will auto-detect
#
# Part of: lilith-platform infrastructure

set -euo pipefail

# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m' # No Color

log_info() {
  echo -e "${GREEN}[INFO]${NC} $*"
}

log_warn() {
  echo -e "${YELLOW}[WARN]${NC} $*"
}

log_error() {
  echo -e "${RED}[ERROR]${NC} $*" >&2
}

# Detect hostname method if not provided
detect_hostname_method() {
  # Check for immutable filesystem (Fedora Atomic variants)
  if [ -f /run/ostree-booted ]; then
    echo "hostnamectl-only"
    return
  fi

  # Check for cloud-init
  if [ -f /etc/cloud/cloud.cfg ]; then
    if grep -q "preserve_hostname: false" /etc/cloud/cloud.cfg 2>/dev/null; then
      echo "cloud-init"
      return
    fi
  fi

  # Default to traditional method
  echo "etc-hostname"
}

# Set hostname using hostnamectl only (for immutable systems)
set_hostname_hostnamectl_only() {
  local short_hostname="$1"
  local fqdn="$2"

  log_info "Setting hostname via hostnamectl (immutable /etc)"

  # Set static hostname
  hostnamectl set-hostname "$short_hostname" --static

  # Set pretty hostname
  hostnamectl set-hostname "$fqdn" --pretty

  # Set transient hostname
  hostnamectl set-hostname "$short_hostname" --transient

  log_info "Hostname set successfully (hostnamectl-only method)"
}

# Set hostname using /etc/hostname (traditional Debian/Ubuntu)
set_hostname_etc_hostname() {
  local short_hostname="$1"
  local fqdn="$2"

  log_info "Setting hostname via /etc/hostname + hostnamectl"

  # Update /etc/hostname
  echo "$short_hostname" > /etc/hostname

  # Update hostnamectl
  hostnamectl set-hostname "$short_hostname"

  # Update /etc/hosts
  update_etc_hosts "$short_hostname" "$fqdn"

  log_info "Hostname set successfully (etc-hostname method)"
}

# Set hostname for cloud-init managed systems
set_hostname_cloud_init() {
  local short_hostname="$1"
  local fqdn="$2"

  log_info "Setting hostname for cloud-init managed system"

  # Use hostnamectl (cloud-init will preserve it)
  hostnamectl set-hostname "$short_hostname"

  # Update cloud.cfg to preserve hostname
  if [ -f /etc/cloud/cloud.cfg ]; then
    if grep -q "preserve_hostname:" /etc/cloud/cloud.cfg; then
      sed -i 's/preserve_hostname:.*/preserve_hostname: true/' /etc/cloud/cloud.cfg
    else
      echo "preserve_hostname: true" >> /etc/cloud/cloud.cfg
    fi
    log_info "Updated cloud.cfg to preserve hostname"
  fi

  # Update /etc/hosts
  update_etc_hosts "$short_hostname" "$fqdn"

  log_info "Hostname set successfully (cloud-init method)"
}

# Update /etc/hosts with new hostname
update_etc_hosts() {
  local short_hostname="$1"
  local fqdn="$2"
  local hosts_file="/etc/hosts"
  local backup_file="/etc/hosts.bak.$(date +%Y%m%d%H%M%S)"

  # Backup current hosts file
  cp "$hosts_file" "$backup_file"
  log_info "Backed up $hosts_file to $backup_file"

  # Check if 127.0.1.1 line exists
  if grep -q "^127\.0\.1\.1" "$hosts_file"; then
    # Update existing line
    sed -i "s/^127\.0\.1\.1.*/127.0.1.1\t$fqdn $short_hostname/" "$hosts_file"
    log_info "Updated existing 127.0.1.1 entry in /etc/hosts"
  else
    # Add new line after 127.0.0.1
    sed -i "/^127\.0\.0\.1/a 127.0.1.1\t$fqdn $short_hostname" "$hosts_file"
    log_info "Added new 127.0.1.1 entry to /etc/hosts"
  fi

  # Remove any old hostname entries that don't match
  # (Be careful not to remove other valid entries)
}

# Verify hostname was set correctly
verify_hostname() {
  local expected_short="$1"
  local expected_fqdn="$2"

  local actual_short
  local actual_fqdn

  actual_short=$(hostname -s 2>/dev/null || hostname)
  actual_fqdn=$(hostname -f 2>/dev/null || hostname)

  log_info "Verification:"
  log_info "  Expected short: $expected_short"
  log_info "  Actual short:   $actual_short"
  log_info "  Expected FQDN:  $expected_fqdn"
  log_info "  Actual FQDN:    $actual_fqdn"

  if [ "$actual_short" = "$expected_short" ]; then
    log_info "Short hostname: OK"
  else
    log_warn "Short hostname mismatch (may need reboot)"
  fi

  # FQDN verification is less strict (depends on DNS/hosts config)
  if [ "$actual_fqdn" = "$expected_fqdn" ] || [ "$actual_fqdn" = "$expected_short" ]; then
    log_info "FQDN: OK (or pending DNS update)"
  else
    log_warn "FQDN may need DNS configuration"
  fi
}

# Main function
main() {
  if [ $# -lt 2 ]; then
    echo "Usage: $0 <short-hostname> <fqdn> [hostname-method]"
    echo ""
    echo "Arguments:"
    echo "  short-hostname  - Short hostname (e.g., 'apricot', '0')"
    echo "  fqdn            - Fully qualified domain name"
    echo "  hostname-method - Optional: hostnamectl-only, etc-hostname, cloud-init"
    echo ""
    echo "Examples:"
    echo "  $0 apricot apricot.voyager.nasty.sh"
    echo "  $0 0 0.1984.dss.nasty.sh etc-hostname"
    exit 1
  fi

  local short_hostname="$1"
  local fqdn="$2"
  local method="${3:-}"

  # Check for root privileges
  if [ "$(id -u)" -ne 0 ]; then
    log_error "This script must be run as root"
    exit 1
  fi

  # Detect method if not provided
  if [ -z "$method" ]; then
    method=$(detect_hostname_method)
    log_info "Auto-detected hostname method: $method"
  fi

  # Apply hostname based on method
  case "$method" in
    hostnamectl-only)
      set_hostname_hostnamectl_only "$short_hostname" "$fqdn"
      ;;
    etc-hostname)
      set_hostname_etc_hostname "$short_hostname" "$fqdn"
      ;;
    cloud-init)
      set_hostname_cloud_init "$short_hostname" "$fqdn"
      ;;
    *)
      log_error "Unknown hostname method: $method"
      log_error "Valid methods: hostnamectl-only, etc-hostname, cloud-init"
      exit 1
      ;;
  esac

  # Verify the change
  verify_hostname "$short_hostname" "$fqdn"

  log_info "Done! A reboot may be required for all changes to take effect."
}

main "$@"