| The Linux file system layout is hierarchical. Files are contained in directories, and directories can have any number of subdirectories. Most operating systems are arranged this way, including UNIX. The following are descriptions of some of the more important directories found on a Linux system: / | The root directory, which is the base of the file system's hierar chical tree structure. A directory is logically viewed as being part of /. Regardless of the disk on which a directory or logical volume is stored, it is logically viewed as a part of the root hierarchy. | /bin | Contains commonly used commands that you issue at the command line all the time. | /boot | The kernel files and those related to the kernel are in this directory. | /dev | Contains host-specific device files. | /etc | Contains host-specific system and application configuration files. The information in this directory is important to the system's operation and is of a permanent nature. There are also additional configuration directories below /etc. | /home | Users' home directories are recommended to be located here. Because the data stored in users' home directories will be modified often and much will be added over time, you can expect this directory to grow in size. | /initrd | An initrd image is needed for loading your SCSI module at boot time or if you are compiling the kernel with ext3 support as a module. | /lib | Libraries and parts of the C compiler are found in this directory. | /lost+found | The lost files directory. Here, you find files that are in use, but are not associated with a directory. These files typically become "lost" as a result of a system crash that caused the link between the physical information on the disk and the logical directory to be severed. The program fsck, which is run at the time of boot, finds these files and places them in the lost+found directory. You will typically see one of these for every disk that you have mounted. | /misc | A directory that is in place to contain miscellaneous information. | /mnt | Directory for mounting, especially temporary mounts, such as floppies and DVD-ROMs. | /opt | The directory under which applications are installed. As a rule, application vendors never specify a particular location for their applications to be installed. Now, with /opt, there is a standard directory under which applications should be installed. This is an organizational improvement for system administrators because they can now expect applications to be loaded under /opt and the application name. | /proc | Images of all running processes are shown here. | /root | Home directory for the user root. | /sbin | Contains commands and scripts used to boot, shut down, and fix file system mounting problems. | /tmp | A free-for-all directory, where any user can temporarily store files. Because of the loose nature of this directory, it should not be used to store anything important, and users should know that whatever they have stored in /tmp can be deleted without notice. Application working files should go in /var/tmp or /var/opt/appname, not in /tmp. | /usr | Most of the UNIX operating system is contained in /usr. Included in this directory are commands, libraries, and documentation. A limited number of subdirectories can appear in /usr. | /var | Holds files that are primarily temporary. Files such as log files, which are frequently deleted and modified, are stored here. Think of this as a directory of "variable" size. Files that an application or command create, at runtime should be placed in this directory, including logfile and spool files. However, some applications, including init scripts, may store state information in /var. |
The following is a long listing of the root (/) directory of the Integrity server used throughout this book: # ls -l / total 244 drwxr-xr-x 2 root root 4096 Jan 16 11:37 bin drwxr-xr-x 3 root root 4096 Jan 16 16:40 boot drwxr-xr-x 18 root root 86016 Jan 28 20:08 dev drwxr-xr-x 66 root root 8192 Jan 28 20:08 etc drwxr-xr-x 3 root root 4096 Jan 16 11:37 home drwxr-xr-x 2 root root 4096 Jun 21 2001 initrd drwxr-xr-x 6 root root 4096 Jan 16 11:32 lib drwx------ 2 root root 16384 Jan 16 10:39 lost+found drwxr-xr-x 2 root root 4096 Aug 29 2001 misc drwxr-xr-x 3 root root 4096 Jan 16 16:40 mnt drwxr-xr-x 2 root root 4096 Aug 23 1999 opt dr-xr-xr-x 59 root root 0 Jan 28 15:07 proc drwxr-x--- 13 root root 4096 Jan 28 21:34 root drwxr-xr-x 2 root root 8192 Jan 16 11:35 sbin drwxrwxrwt 10 root root 77824 Jan 29 04:02 tmp drwxr-xr-x 17 root root 4096 Jan 16 11:26 usr drwxr-xr-x 26 root root 4096 Jan 16 11:35 var #
You'll be working extensively in some of these directories in upcoming chapters. You'll become familiar with the contents of some of these directories in upcoming chapters, such as /boot and /proc in the kernel chapter. The previous sections of this chapter covered some of the most important aspects of working with a Linux system, such as adding and partitioning a disk, mounting the disk, the layout of the file system, and log files. This working knowledge of the file system is important Linux knowledge. The next section covers configuration of the Smart Array controller. |
