Basic Concepts

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This chapter introduces you to basic concepts which are useful when getting started with a Kubuntu system.

Table of Contents

Directories and File Systems

Permissions

Root And Sudo

Start a Program Manually with Root Privileges

User Management

Terminal

Starting the Terminal
Common Commands
Switching to Console mode
Disabling the beep sound in Terminal mode

Restart Kubuntu without rebooting

Text Editing

Directories and File Systems

In Linux and Unix everything is a file. Directories are files, files are files, and devices are files. Devices are usually referred to as nodes; however, they are still files.

Linux and Unix file systems are organized in a hierarchical, tree-like structure. The highest level of the file system is the / or root directory. All other files and directories exist under the root directory. For example, /home/konqi/kubuntu.odt shows the correct full path, or absolute path, to the kubuntu.odt file that exists in the konqi directory, which is under the home directory, which in turn is under the root (/) directory.

Underneath the root (/) directory is a set of important directories common to most Linux distributions. The following is a listing of common directories that are directly under the root (/) directory:

/bin: Important commands, which historically have been binary, but may also be shell scripts.
/boot: Boot configuration files, kernels, and other files needed at boot time.
/dev: The device files.
/etc: Configuration files, startup scripts, etc.
/home: Home directories for different users.
/initrd: Used when creating a customized initial RAM Disk.
/lib: System libraries.
/lost+found: Provides a lost+found system for files that exist under the root (/) directory.
/media: Automatically mounted (loaded) removable media such as CDs, digital cameras, etc.
/mnt: Manually mounted filesystems on your hard drive.
/opt: Provides a location for optional (3rd party) applications to be installed; these are usually statically compiled and can be used in other versions or Linux distributions.
/proc: Special dynamic directory that maintains information about the state of the system, including currently running processes.
/root: Root user's home directory, pronounced "slash-root".
/sbin: Important system binaries and scripts, usually intended to be run as the root user.
/srv: Can contain files that are served to other systems.
/sys: Similar to the /proc filesystem, but contains system information not related to running processes.
/tmp: temporary files.
/usr: Applications and read-only files that are mostly available for all users to access.
/var: variable files such as logs and databases.