POS420 Introduction to Unix Philip Robbins March 19

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/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, X 11, 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/pos 420/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 man 1: 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. man 2: System calls. This section describes all of the system calls (requests for the kernel to perform operations). man 3: 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. man 4: 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 man 5: 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. man 6: Games. This chapter documents games, demos, and generally trivial programs. Different people have various notions about how essential this is. man 7: 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. man 8: 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 man 6: 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 F 1 (for tty 1) - F 2 (for tty 2) … F 6 (for tty 6) - Hold Ctrl + Alt, press F 7 (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, 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 @ 800 PM

Assignment #1 • • • 30 Questions Use Print. Screen (Prt. Sc) 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