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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.
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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 – manual pages • ls– list directory contents • pwd– print working directory • passwd– change password • sudo– execute command as superuser • su– login as superuser • shutdown – shutdown
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
/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
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
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
sudo fdisk -l • Use fdisk to list all partitions (as root)
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
Shells • What is an OS shell? • Types • ksh, tcsh, csh, sh, bash • What shell are you running? • echo $SHELL
Shells • csh
Directory Notation • / • Represents a directory • /. • Represents current directory • /.. • Represents the parent directory • /~ • Represents a user’s home directory
File Permissions • Octal (numerical) Representation
Run Levels • runlevel • Previous runlevel, current runlevel • init • Change between run levels (process id 1) • telinit • Change system run level (user process)
