./generate_ssh_key.sh -c "John Doe <john.doe@example.com>"

README.md

Usage:

./generate_ssh_key.sh -c "John Doe <john.doe@example.com>"

generate_ssh_key.sh

#!/usr/bin/env bash
set -euo pipefail

SSH_DIR="${HOME}/.ssh"
KEY_FILE="${SSH_DIR}/id_rsa"

usage() {
  cat <<EOF
Usage:
  $(basename "$0") -c <comment>

Description:
  Generate a non-interactive ed25519 SSH key with no passphrase.
  Existing keys will be backed up.

Options:
  -c, --comment   Comment to embed in the public key
  -h, --help      Show this help message

Example:
  $(basename "$0") -c "John Doe <john.doe@example.com>"
EOF
}

COMMENT=""

while [[ $# -gt 0 ]]; do
  case "$1" in
    -c|--comment)
      COMMENT="$2"
      shift 2
      ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "Unknown argument: $1"
      echo
      usage
      exit 1
      ;;
  esac
done

if [[ -z "${COMMENT}" ]]; then
  echo "Error: comment is required"
  echo
  usage
  exit 1
fi

mkdir -p "${SSH_DIR}"
chmod 700 "${SSH_DIR}"

BACKUP_SUFFIX="$(date +%Y%m%d_%H%M%S)"

if [[ -f "${KEY_FILE}" ]]; then
  mv "${KEY_FILE}" "${KEY_FILE}.${BACKUP_SUFFIX}.bak"
fi

if [[ -f "${KEY_FILE}.pub" ]]; then
  mv "${KEY_FILE}.pub" "${KEY_FILE}.pub.${BACKUP_SUFFIX}.bak"
fi

ssh-keygen \
  -t ed25519 \
  -C "${COMMENT}" \
  -f "${KEY_FILE}" \
  -N "" \
  -q

chmod 600 "${KEY_FILE}"
chmod 644 "${KEY_FILE}.pub"

echo "SSH key generated successfully:"
echo "Private key: ${KEY_FILE}"
echo "Public key : ${KEY_FILE}.pub"