POS/420
Introduction to Unix
Philip Robbins – March 19, 2013 (Week 2)
University of Phoenix Mililani Campus
Agenda: Week 2
• Quiz #1 Due (Review & Grade)
• Week 2
- File Structure
- Basic Terminal Commands
- Permissions
• In Class Lab (Assignment) #1 Due Today
• Take Quiz #2
Review Week 1 List of Commands
man
ls
pwd
passwd
sudo
su
shutdown
– manual pages
– list directory contents
– print working directory
– change password
– execute command as superuser
– login as superuser
– shutdown
Linux File System Structure
Linux File System Structure
root (/)
File Structure: Binaries
• What’s the difference between:
- /bin
- /sbin
- /usr/bin
- /usr/sbin
File Structure: Binaries
• What’s the difference between: /bin & /usr/bin
When UNIX was first written, /bin and /usr/bin physically
resided on two different disks: /bin being on a smaller
faster (more expensive) disk, and /usr/bin on a bigger
slower disk.
/bin
• Essential User Command Binaries
- Contain commands used by both system administrators
and users.
- There must be no subdirectories in /bin.
/boot
• Static files of the boot loader
- Contains everything for the boot process (at boot time).
- Does not include boot configuration files not needed at
boot time.
- Stores data that is used before the kernel begins
executing.
- OS Kernel is stored in either / or /boot.
/dev
• Device Files
- Location of special or devices files.
/etc
• Host-specific system configuration
- Contains configuration files.
- Must be Static and cannot be an executable binary.
- Required in /etc: opt, X11, sgml, xml
/etc
/srv
•
-
Data for services provided by this system.
Contains site-specific data which is served by this system.
Naming methodology not specified.
e.g. /srv/ftp, /srv/pos420/www
Data that is of interest to a specific user should go into that
users home directory.
/tmp
• Temporary Files
- Must be made available for programs that require the use
of temporary files.
- Recommend that /tmp files be deleted upon system reboot.
/usr
•
-
User Hierarchy
Second major section of the file system.
Used for shareable, read-only data.
Required directories:
bin
- essential command binaries
sbin
- essential system binaries
include
- header files used by C programs
lib
- object files, binaries, libraries
local
- put apps you build yourself here
share
- shared (Static)
/usr
• What’s the difference between: /usr & /usr/local
/usr/share/man
• Directory for System Manual Pages
man1:
User programs Manual pages that describe publicly accessible commands are
contained in this chapter. Most program documentation that a user will need to use
is located here.
man2:
System calls. This section describes all of the system calls (requests for the kernel
to perform operations).
man3:
Library functions and subroutines. Section 3 describes program library routines
that are not direct calls to kernel services. This and section 2 are only really of
interest to programmers.
man4:
Special files. Section 4 describes the special files, related driver functions, and
networking support available in the system. Typically, this includes the device files
found in /dev and the kernel interface to networking protocol support.
/usr/share/man
• Directory for System Manual Pages
man5:
File formats. The formats for many data files are documented in the section 5.
This includes various include files, program output files, and system files.
man6:
Games. This chapter documents games, demos, and generally trivial programs.
Different people have various notions about how essential this is.
man7:
Miscellaneous. Manual pages that are difficult to classify are designated as being
section 7. The troff and other text processing macro packages are found here.
man8:
System administration. Programs used by system administrators for system
operation and maintenance are documented here. Some of these programs are
also occasionally useful for normal users.
/usr/share/man
• Manual Section Summary
man apropos
apropos
apropos
man6:
Games. This chapter documents games, demos, and generally trivial programs.
Different people have various notions about how essential this is.
/var
• Variable Hierarchy
- Contains variable data files.
- Spool files & directories, logging data, temporary files (for
system reboots).
- Not Shareable.
- e.g. /var/log, /var/mail, /var/cache, /var/crash (dump files)
- Can be placed in /usr/var. (If separate partition for /var is
not possible).
/var
•
•
-
Use the “more” command to view files.
man more for more information
view syslog
view kern.log
Also use the “head” and “tail” command to view files.
man head & tail for more information
know how to head & tail –n lines of a file
/proc
• Kernel and process information virtual file system
- Used for handling process and system information
- Kernel and memory information
man ps
top
FHS Compliant System
• Rationale:
- Not all files can be shared
- Static and Variable files should be segregated
- Static files can be stored on read-only media
- Different backup schedules
man fdisk
sudo fdisk -l
• Use fdisk to list all partitions (as root)
fdisk
Typical Partitions
Virtual Terminals (TTY)
• Six tty (1 – 6)
- Hold Ctrl + Alt, press F1 (for tty1)
- F2 (for tty2) … F6 (for tty6)
- Hold Ctrl + Alt, press F7 (to return to GUI)
- Press and hold Ctrl + Alt to switch between VM and GUI
who
who
User ($) vs. Root (#)
Shells
• What is an OS shell?
• Types
- ksh, tcsh, csh, sh, bash
• What shell are you running?
- echo $SHELL
Shells
• csh
man usermod
man ssh
ssh
Directory Notation
• /
• /.
• /..
• /~
-
Represents a directory
Represents current directory
Represents the parent directory
Represents a user’s home directory
File Permissions
File Permissions
• Octal (numerical) Representation
man chmod
man chown
man chgrp
File Permissions Command Summary
Run Levels
• runlevel
- Previous runlevel, current runlevel
• init
- Change between run levels (process id 1)
• telinit
- Change system run level (user process)
runlevel
vi (text editor)
Review essential user commands (/bin)
Break
• Let’s take a break… RETURN @ 800PM
Assignment #1
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30 Questions
Use PrintScreen (PrtSc)
Work in groups (optional)
Submit individual assignments!
Post to OLS. -- use pdf format.
Due before you leave class tonight.
Quiz: Week 2
• 10-15 minutes