System Administration in Software

Generator Code39 in Software System Administration

Although all the files in your Linux system are connected into one overall directory tree, parts of that tree may reside on different storage devices such as hard drives or CD-ROMs Files on a particular storage device are organized into what is referred to as a file system A file system is a formatted device, with its own tree of directories and files Your Linux directory tree may encompass several file systems, each on different storage devices On a hard drive with several partitions, you have a file system for each partition The files themselves are organized into one seamless tree of directories, beginning from the root directory For example, if you attach a CD-ROM to your system, a pathname will lead directly from the root directory on your hard disk partition s file system to the files in the CD-ROM file system

operating systems, such as Windows, IBM OS, Unix, and SGI Within Linux a variety of file systems are supported, including several journaling systems like ReiserFS and ext3 A file system has its files organized into its own directory tree You can think of this as a subtree that must be attached to the main directory tree The tree remains separate from your system s directory tree until you specifically connect it For example, a floppy disk with Linux files has its own tree of directories You need to attach this subtree to the main tree on your hard drive partition Until they are attached, you cannot access the files on your floppy disk

File System Hierarchy Standard (FHS)

Linux organizes its files and directories into one overall interconnected tree, beginning from the root directory and extending down to system and user directories The organization and layout for the system directories are determined by the file system hierarchy standard (FHS) The FHS provides a standardized layout that all Linux distributions should follow in setting up their system directories For example, there must be an /etc directory to hold configuration files and a /dev directory for device files You can find out more about FHS, including the official documentation, at pathnamecom/fhs Linux distributions, developers, and administrators all follow the FHS to provide a consistent organization to the Linux file system Linux uses a number of specifically named directories for specialized administrative tasks All these directories are at the very top level of your main Linux file system, the file system root directory, represented by a single slash, / For example, the /dev directory holds device files, and the /home directory holds the user home directories and all their user files You have access to these directories and files only as the system administrator (though users normally have read-only access) You need to log in as the root user, placing yourself in a special root user administrative directory called /root From here, you can access any directory on the Linux file system, both administrative and user

Root Directory: /

The subdirectories held in the root directory, /, are listed in Table 29-1, along with other useful subdirectories Directories that you may commonly access as an administrator are the /etc directory, which holds configuration files; the /dev directory, which holds dynamically

29:

Directory / /boot /home /sbin /dev /etc /etc/opt /etc/X11 /bin /lib /lib/modules /media /mnt /opt /proc /sys /tmp /usr /var

Function Begins the file system structure called the root Holds the kernel image files and associated boot information and files Contains users home directories Holds administration-level commands and any commands used by the root user Holds dynamically generated file interfaces for devices such as the terminal and the printer (see udev: Device Files in 31) Holds system configuration files and any other system files Holds system configuration files for applications in /opt Holds system configuration files for the X Window System and its applications Holds the essential user commands and utility programs Holds essential shared libraries and kernel modules Holds the kernel modules Holds directories for mounting media-based removable file systems, such as CD-ROMs, floppy disks, USB card readers, and digital cameras Holds directories for additional file systems such as hard disks Holds added software applications (for example, KDE on some distributions) Process directory, a memory-resident directory that contains files used to provide information about the system Holds the sysfs file system for kernel objects, listing supported kernel devices and modules Holds temporary files Holds those files and commands used by the system; this directory breaks down into several subdirectories Holds files that vary, such as mailbox, web, and FTP files