Can I set my user account to have no password?

You can't do that using the GUI tool, but you can using the terminal.

1. First, if your user has sudo privileges, you must enable its NOPASSWD option. Otherwise, sudo will ask for a password even when you don't have one, and won't accept an empty password.

   To do so, open the sudoers configuration file with sudo visudo, and add the following line to the file, replacing david with your username:

   david ALL=(ALL) NOPASSWD:ALL
   

   Close the editor to apply the changes, and test the effect on sudo in a new terminal.

2. Delete the password for your user by running this command:

   sudo passwd -d `whoami`
   

If you ever get prompted for a password, just type enter and it should work. I've tested this answer with LightDM, the lock screen, sudo, gksu and it works, but there's one more step to get it to work with pkexec (thanks muru).

Warning: Be careful once you remove your password using this method, you won't be able to authenticate yourself to prove you have admin rights, in a GUI or in the terminal (like installing an application using Synaptic, or using sudo through the command-line). This is because of bug #1168749.

Only do this if the user is not the only admin user.

This has been tested on Ubuntu 12.04 and 12.10.

1. Make sure that you click on Unlock to be able to accomplish the tasks below:

   

2. Go into user accounts, and click on the password field:

   

3. Once the window opens, click on the down arrow to the right of "Action"...

   

4. and change it to "Log in without a password", and then click on "Change":

   

5. Optionally, you can also enable automatic log-in, like this:

   

To give the user a password again after running this procedure, you can't use a GUI (bug #882255), you have to use the command-line:

1. Log in as another user with admin priveleges. (Remember, the original one cannot run with admin privileges without a password using this method.)

2. Run the following in a terminal:

    sudo passwd <username>
   

Again, I must warn you that once you remove the password, you won't be able to authenticate yourself in the GUI or a terminal, like installing an application using Synaptic, or using sudo on the command-line.

I think it's possible to do this, but will get you into trouble once you try to install updates or anything else that requires sudo; as you need an account with sudo access (and a password) in order to install.

Your best options seem to be:

• Use the Guest account that doesn't have a password. Thereby leaving a default account with password.
• Hellbent on an account without password? Strongly recommend not doing this: Add a new user account (with password), then change it to be the equivalent as blank. To do this:
  1. create a user (either via GUI or useradd, etc). Then,
  2. CTRL-ALT-T to open terminal. Next,
  3. gksu gedit nano -B /etc/shadow then find the new user and change the existing password hash with: U6aMy0wojraho -- so it looks something like: newuser:U6aMy0wojraho:13996:0:99999:7:::

• Best solution to your question: Choose to automatically log in your account, which is likely the main benefit you're after. to do this:

  1. press CTRL-ALT-T (to open terminal). In Terminal, type:

     sudo gedit /etc/lightdm/lightdm.conf
     

     add the lines:

     autologin-user=YOURUSERNAME
     autologin-user-timeout=0
     

     replace YOURUSERNAME -- with an actual username on your system.

Looks like, an empty password doesnt match Password Complexity requirements.

This is what I found in man passwd

As a general guideline, passwords should consist of 6 to 8 characters including one or
       more characters from each of the following sets:

       ·   lower case alphabetics

       ·   digits 0 thru 9

       ·   punctuation marks

       Care must be taken not to include the system default erase or kill characters.  passwd will reject any password which is not
       suitably complex.

EDIT: Unfortunately, you can't set the password to empty through that UI.

http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/quantal/gnome-control-center/quantal-proposed/view/head:/panels/user-accounts/um-password-dialog.c#L358

is the function which decides whether to enable the "Change" button or not.

    if (strlen (password) < MIN_PASSWORD_LEN) {
            can_change = FALSE;
            if (password[0] == '\0') {
                    tooltip = _("You need to enter a new password");
            }
            else {
                    tooltip = _("The new password is too short");
            }
    }
    else if (strcmp (password, verify) != 0) {
            can_change = FALSE;
            if (verify[0] == '\0') {
                    tooltip = _("You need to confirm the password");
            }
            else {
                    tooltip = _("The passwords do not match");
            }
    }
    else if (!um->old_password_ok) {
            can_change = FALSE;
            if (old_password[0] == '\0') {
                    tooltip = _("You need to enter your current password");
            }
            else {
                    tooltip = _("The current password is not correct");
            }
    }
    else {
            can_change = TRUE;
            tooltip = NULL;
    }

    gtk_widget_set_sensitive (um->ok_button, can_change);

The minimum password len 6 is hardcoded :(

http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/quantal/gnome-control-center/quantal-proposed/view/head:/panels/user-accounts/um-password-dialog.c#L39

#define MIN_PASSWORD_LEN 6

Its a GUI interface and that is what is preventing you from making it a blank password.

If there was a way it would have to be done via terminal.

But, in the end you have to enter the system via the GUI and even if you did change the password to blank the GUI would prevent that. So unless you want to change to a non GUI interface it is simply not possible.

It is possible to change password after deletion. You need just to boot in recovery mode. Here you'll find a nice tutorial: http://www.psychocats.net/ubuntu/resetpassword

In short what you'll find on the link above:

1. you have to reboot into recovery mode. (to get the boot menu to show, you have to hold down the Shift key during bootup)

2. In boot-up menu select "Drop to root shell prompt" option

3. type on console one by one

   ls /home
   passwd username
   passwd susan
   exit
   

   then reboot normal