Computer History Notes - Herong's Tutorial Notes - v3.13, by Herong Yang
UNIX File System Hierarchy
This section provides a quick introduction of UNIX file system hierarchy.
On a UNIX system, almost all resources are represented as files in a single file system hierarchy.
For example, the first floppy disk drive is represented as a device file: /dev/fd0. Data can be read from and write to a floppy disk directly through /dev/fd0. But if a floppy disk has file system structure, it can also be mounted to the file system hierarchy.
The "df" command displays usage information of physical storage devices that are mounted on the current file system hierarchy:
#df Filesystem 1024-blocks Used Available Capacity Mounted on /dev/hda1 198275 134358 53672 71% / /dev/hda3 92333 1 87564 0% /mnt/backup /dev/df0 1676 960 716 57% /mnt/floppy
The output tells us that 3 storage devices with file systems are mounted on the file system hierarchy:
UNIX system also has a very interesting special file called /dev/null, representing an empty file for reading and a black hole for writing. /dev/null is very useful for truncating log files that are currently in use. Here is an example of commands to rotate the mail.log file once a day on a Solaris system:
#vi /usr/lib/newsyslog cd /var/log test -f mail.log.2 && mv mail.log.2 mail.log.3 test -f mail.log.1 && mv mail.log.1 mail.log.2 test -f mail.log.0 && mv mail.log.0 mail.log.1 mv mail.log mail.log.0 cp /dev/null /var/log/mail.log chmod 644 /var/log/mail.log kill -HUP `cat /etc/syslog.pid` #crontab -e root 59 23 * * 6 /usr/lib/newsyslog
Table of Contents
2002 - .NET Framework Developed by Microsoft
1995 - PHP: Hypertext Preprocessor Created by Rasmus Lerdorf
1995 - Java Language Developed by Sun Microsystems
1991 - WWW (World Wide Web) Developed by Tim Berners-Lee
1991 - Gopher Protocol Created by a University of Minnesota Team
1984 - X Window System Developed a MIT Team
1984 - Macintosh Developed by Apple Inc.
1983 - "Sendmail" Mail Transfer Agent Developed by Eric Allman
1979 - The Tcsh (TENEX C Shell) Developed by Ken Greer
1978 - Bash (Bourne-Again Shell) Developed by Brian Fox
1978 - The C Shell Developed by Bill Joy
1977 - The Bourne Shell Developed by Stephen Bourne
1977 - Apple II Designed by Steve Jobs and Steve Wozniak
1976 - vi Text Editor Developed by Bill Joy
1974 - Internet by Vinton Cerf
1972 - C Language Developed by Dennis Ritchie
1971 - FTP Protocol Created by Abhay Bhushan
►1970 - UNIX Operating System Developed by AT&T Bell Labs
Command Interpreters and Command Pipelines