Post on 29-Mar-2015
POS/420
Philip Robbins – March 19, 2013 (Week 2)University of Phoenix Mililani Campus
Introduction to Unix
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 – manual pages
ls – list directory contents
pwd – print working directory
passwd – change password
sudo – execute command as superuser
su – login as superuser
shutdown – 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 Pagesman1: 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 Pagesman5: 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
• 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