Create new user in Linux and add it to sudo or other groups.

create-user

#!/usr/bin/env bash

## date:   2022/02/21
## author: duruyao@gmail.com
## desc:   the shortcut to create user
## usage:  create-user [NEW_USERNAME] [NEW_USER_PASSWD]

set -euo pipefail

function warning_ln() {
  # usage: warning_ln "warning message"
  printf "\033[1;32;33m%s\n\033[m" "${1}"
}

if [ "${USER}" != "root" ]; then
  warning_ln "Warning: The user 'root' may be required."
fi

NEW_USERNAME=""
if [ $# -gt 0 ]; then NEW_USERNAME="$1"; fi
if [ -z "${NEW_USERNAME}" ]; then
  printf "[*] Input a new username: "
  read -r NEW_USERNAME
fi

NEW_USER_PASSWD=""
if [ $# -gt 1 ]; then NEW_USER_PASSWD="$2"; fi
if [ -z "${NEW_USER_PASSWD}" ]; then
  printf "[*] Input the new user's password: "
  read -r NEW_USER_PASSWD
fi

useradd -ms /bin/bash "${NEW_USERNAME}"

echo "${NEW_USERNAME}":"${NEW_USER_PASSWD}" | chpasswd

if [ -n "$(getent group sudo)" ]; then
  add_user_to_group=""
  printf "[*] Would you want add '%s' to the group 'sudo'? [Y/n] " "${NEW_USERNAME}"
  read -r add_user_to_group
  if ! echo "${add_user_to_group}" | grep -q -E "n|no|N|No|NO"; then
    usermod -aG sudo "${NEW_USERNAME}"
  fi
fi

if [ -n "$(getent group docker)" ]; then
  add_user_to_group=""
  printf "[*] Would you want add '%s' to the group 'docker'? [Y/n] " "${NEW_USERNAME}"
  read -r add_user_to_group
  if ! echo "${add_user_to_group}" | grep -q -E "n|no|N|No|NO"; then
    usermod -aG docker "${NEW_USERNAME}"
    if [ -n "$(command -v docker-check.sh)" ]; then
      line="alias docker=\"docker-check.sh\""
      echo -e "\n${line}\n" >>"$(eval echo ~"${NEW_USERNAME}")"/.bashrc
    fi
  fi
fi

if [ -n "$(command -v samba)" ] && [ -f "/etc/samba/smb.conf" ]; then
  add_user_to_samba=""
  printf "[*] Would you want add '%s' to the 'samba'? [Y/n] " "${NEW_USERNAME}"
  read -r add_user_to_samba
  if ! echo "${add_user_to_samba}" | grep -q -E "n|no|N|No|NO"; then
    printf "%s\n%s" "${NEW_USER_PASSWD}" "${NEW_USER_PASSWD}" | smbpasswd -a "${NEW_USERNAME}"
    if ! grep -q -E "${NEW_USERNAME}" /etc/samba/smb.conf; then
      cp /etc/samba/smb.conf /etc/samba/smb.conf.bak
      sed -i "s/valid users =/valid users = ${NEW_USERNAME},/g" /etc/samba/smb.conf
      sed -i "s/valid users = ${NEW_USERNAME}, \%S/valid users = \%S/g" /etc/samba/smb.conf
    else
      warning_ln "Warning: The user '${NEW_USERNAME}' exists in '/etc/samba/smb.conf'"
    fi
  fi
fi