UnixLinux 1 Unix History Unix History Originally developed

Unix/Linux 1

Unix History • Unix History – Originally developed in 1969 at Bell Labs by Ken Thompson and Dennis Ritchie – Berkeley UNIX began in 1977: BSD (Berkeley Software Distribution) – Two main directions: BSD and System V • Some of today’s main Unix versions – Mostly BSD (4. 4 BSD-Lite) • BSD, Free. BSD, Mac OS X – Mostly Sys. V: • Solaris (Sun Microsystems), HP-UX (HP), IRIX (by SGI) 2

Some Unix Versions 3

Unix Basics • The OS is divided into – Kernel – Shell – Tools & Applications • Basic Unix features – Multitasking – Multiuser – Portability • POSIX – Portable Operating System Interface for uni. X – Networking capabilities 4

Unix Basics – Con’t • These features result in – Multi-user concepts • • • User privilege File permissions Process ownership and priorities Communication with users Disk quotas – Superuser account • Unrestricted access for superuser • Requires strong authentication – Security considerations • Protect user data • Protect communication • Protect superuser account 5

Linux • The Linux kernel was created by Linus Torvalds • Defines only an OS kernel • Distributions – Redhat, Su. SE, Debian, Turbo. Linux… • Make sure you have a login name and password. Use passwd to change your password • If you do not have a graphical user interface, use vi to edit files • Documentation is stored on-line, It can be accessed by the man command 6

Ubuntu Linux • Various organizations package the Linux kernel and system programs as Linux distributions – SUSE, Fedora, Ubuntu, Debian… • Canonical Ltd. (www. canonical. com) - the sponsor of Ubuntu Linux – supports many similar Linux distributions – Ubuntu: GNOME desktop – Kubuntu: www. kubuntu. org, KDE desktop – Edubuntu: www. edubuntu. org: school app. – Xubuntu: www. xubuntu. org: lightweight 7

Tasks of System Admin. • • • Adding and removing users Adding and removing hardware Performing backups Installing new software Monitoring the system Troubleshooting Maintaining local documentation Auditing security Helping user 8

Simple Linux Commands • • • • date – display the date ls – list the files in the current directory more – display files one screen at a time cat – display the contents of a file wc – displays lines, words, and characters cp, mv, rm, pwd, mkdir, cd, rmdir, chmod, head – show the first few lines of a file – determine a file type tail – show the last few lines of a file cal – display calendar kill – terminate a running command lpr – send a job to the printer grep – searches a file for a specific pattern …. 9

vi editor • One of the most powerful editors in Linux/Unix • Two different modes: – Command mode: most of the keys perform the vi command – Insert mode: the mode where what you type is inserted into the document • When using vi, it is necessary to make transitions from one mode to the other 10

Booting and Shutting Down – Basic Steps • • • Load and init the kernel Detect and config the devices Create spontaneous processes Operator intervention (manual boot only) System startup scripts Multi-user operation 11

Kernel Initialization • Kernel is a program • Path is vendor dependent – Solaris - /kernel/genunix – Linux – depends, /vmlinuz, /boot/vmlinuz • Two stage process – Boot loader read from disk or tape – Kernel loaded into memory 12

Bootstrapping Bootstrap loader (“boot sector”) 1 2 BIOS loader 0 x 0000100 0 x 0001000 3 Loader OS 0 x 0008000 0 x 000 A 000 Primary Memory 4. Initialize hardware 5. Create user environment 6. … 13

Kernel Initialization – Con’t • Hardware configuration – Detect and initialize devices built into the kernel – Probes for additional device info and other devices • System Processes – init – Spontaneous processes • Boot Loaders – LILO – GRUB • “info grub” on your shell prompt – Multibooting 14

Kernel Initialization – Con’t • Startup Scripts – Location, content, and organization of the startup scripts varies by the system – /etc/rc* scripts run programs that start with “S” in the /etc/rc*. d directories – /etc/rc*. d startup scripts are usually linked to scripts in a common /etc/init. d directory – Example: • sudo /etc/init. d/networking start • sudo /etc/init. d/networking restart 15

Starting all the other processes • • • Runlevel 0: Brings the system down 1: Brings the system to single-user (S, recovery: /etc/rc. S. d) mode 2: Multiuser mode, graphical login, all scheduled system services running 3, 4, 5: Multiuser mode, graphical login, all scheduled system services running (for system customization, runlevels 2 -5 are identical) • 6: Reboots the system • Default runlevel: 2 16

Rebooting and Shutting down • halt, reboot, poweroff • shutdown –h 09: 30 “Going down for scheduled maintenance” • telinit – telinit 1: take the system to single-user mode • Never just turn off a Linux computer. Just like other OS’s, it needs to be told you want to finish using it. 17

Ubuntu Software Package • A software package is the collection of scripts, programs, files and directories required to install and run applications, utilies, and system software

aptitude • Install and remove package using aptitude • Examples – sudo aptitude install tcsh: install tcsh shell – sudo aptitude install apache 2. 2 -comm – sudo aptitude remove tcsh

packages • /etc/apt/sources. list – Repositories APT (Advanced Package Tool) searches when asked to find or install a package – Software sources window – deb: packages of executable files – deb-src: packages of source files

packages • /etc/apt/sources. list – type URL repository category-list – Category • main: Ubuntu-supported open-source software • universe: Community maintained open-source software • multiverse: software restricted by copyright or legal issues • restricted: proprietary device driver