Operation Manual

used to log on to the Pi initially. Just follow these steps:
1. Log in to the Pi using the existing user account (user name pi and password raspberry if you’re using the recommended
Debian distribution).
2. Type the following as a single line:
sudo useradd -m -G adm,dialout,cdrom,audio,plugdev,users,
lpadmin,sambashare,vchiq,powerdev username
This creates a new, blank user account. Note that the command should be typed as a single line, with no spaces after the
commas.
3. To set a password on the new account, type sudo passwd username followed by the new password when prompted.
To explain what just happened: the command sudo tells the operating system that the command you’re typing should be run as if
you were logged in as the root account. The useradd command says you want to create a new user account. The -m section—
known as a flag or an option—tells the useradd program to create a home directory where the new user can store his or her
files. The big list following the -G flag is the list of groups of which the user should be a member.
Users and Groups
In Linux, each user has three main attributes: their User ID (UID), their Group ID (GID) and a list of supplementary group memberships. A user can be a
member of as many groups as he or she pleases, although only one of these can be the user’s primary group. This is usually a self-named group matching the
user name.
Group membership is important. While users can be granted direct access to files and devices on the system, it’s more common for a user to receive access to
these via group membership. The group audio, for example, grants all members the ability to access the Pi’s sound playback hardware. Without that
membership, the user won’t be listening to any music.
To see a user’s group memberships, type groups username at the terminal. If you use this on the default user pi, you’ll see the list of groups any new
member should join to make use of the Pi. This is where the information used in step 2 of the preceding procedure was found.
File System Layout
The content of the SD card is known as its file system, and is split into multiple sections each with a particular purpose. Although
it’s not necessary for you to understand what each section does in order to use the Raspberry Pi, it can be helpful background
knowledge should anything go wrong.
Logical Layout
The way Linux deals with drives, files, folders and devices is somewhat different to other operating systems. Instead of having
multiple drives labelled with a letter, everything appears as a branch beneath what is known as the root file system.
If you log in to the Pi and type ls / you’ll see various directories displayed (see Figure 2-3). Some of these are areas of the SD
card for storing files, while others are virtual directories for accessing different portions of the operating system or hardware.
Figure 2-3: A directory listing for the Pi’s root file system