====== Linux Users and Groups Commands ======
===== Simple Example =====
<code>
useradd user007 -m -s /bin/bash
passwd user007
adduser user007 www-data
</code>

===== Adding Group =====
Adding group someusername with a specific gid of 5001
<code bash>
groupadd -g 5001 someusername
</code>

===== Adding User =====
Addding user someusername with a specific id, assign to gid 5001, etc

<code bash>
useradd -d /home/someusername -g 5001 -m -s /bin/bash -u 5001 -p somepassword someusername
</code>

===== Appending a group to an existing user as secondary group =====
Appending a group to an existing user as secondary group

<code>
usermod -a -G <group_name> <user_name>
</code>

Or

<code>
adduser <user_name> <group_name>
</code>

===== View a user id =====
<code>
id <user_name>
</code>

===== Changing password =====
This was done as root
<code>
echo "newpassword" | passwd --stdin <userid>
</code>


====== Sample ======
  * Create group and user vmail and add user to group
  * Create /home/vmail directory and make that the default home directory for user

<code bash>
groupadd -g 5000 vmail
useradd -d /home/vmail -g 5000 -m -s /bin/bash -u 5000 -p somepassword vmail
usermod -a -G vmail vmail
id vmail
</code>

  * Add user vmail to additional groups adm and sudo

<code>
adduser vmail adm
adduser vmail sudo
</code>

===== Adding User - Alternative =====
Adding group and user without specifying id.  Also sets password.
<code bash>
UN=vipanicker
UN1="Vinod Panicker"
UN2="password"
groupadd $UN
useradd -d /home/$UN -g $UN -m -s /bin/bash -p somepassword $UN --comment "$UN1"
#useradd -d /home/$UN -g $UN -G wheel -m -s /bin/bash -p somepassword $UN --comment "$UN1"
echo "$UN2" | passwd --stdin $UN
</code>

===== Adding User - Ubuntu =====
Adding user johndoe - Run as root.  This also gives johndoe sudo priviledges!
<code bash>
NEWUSER=vidman
groupadd ${NEWUSER}
useradd -d /home/${NEWUSER} -g ${NEWUSER} -G adm,cdrom,sudo,dip,plugdev,sambashare,lpadmin -m -s /bin/bash -p somepassword ${NEWUSER}
</code>

Setting password
<code bash>
passwd ${NEWUSER}
</code>

===== Locking User - Ubuntu =====
To disable or lock the password of an user account. This action prepends a ! to the password hash and the password will no longer match anymore.

<code>
# Disable user01's password
passwd -l user01 
</code>
To unlock user01
<code>
# Enable password
passwd -u user01
</code>

===== Passwords =====
Tested only on redhat

<code bash>
# List password policy
chage -l snathan
# Change to no expiry
chage -m 0 -M 99999 snathan
# Change password
passwd snathan
</code>