Linux Basics Part 1 OSU Picture © Greg Keene

Introductions Lance Albertson Greg Lund-Chaix source:

Goals for this Talk Linux Overview Linux distributions System overview More detail: permissions, processes, package management, services

Linux Overview Unix-like operating system Free, open source software Runs servers, desktops, phones, tablets, network equipment and more.

Linux Statistics Supercomputers More than 90% of the top 500 Number of distributions More than 350 Number of developers 1,000 developers contributed in 2010 Number of commits to linux kernel last year 195,579 commits in 2010

Linux Distributions Packaging of applications around a Linux kernel Different distributions have different target audiences Distribution lifecycles vary source:

Common Linux Distributions Fedora / RedHat Enterprise / CentOS Debian / Ubuntu / Mint Gentoo / Arch source:

Choosing a Distribution Server/desktop/other Existing infrastructure Admin experience Support contract Release supported lifetime

Linux System Overview source: wikipedia

bash: Bourne Again SHell Default shell on Linux Originally based off of the Bourne Shell (sh) Learn it, live it, love it

Basic bash commands ls *.txt file1.txt file2.txt file3.txt ls *.txt > list for i in `cat list`; do cp "$i" "$i".bak ; done ls *.txt* file2.txt file1.txt.bak file2.txt file2.txt.bak file3.txt file3.txt.bak

Documentation Most packages include man pages for documentation More extensive than the - -help flag on CLI Stored in different 'sections' Picture © Flickr user 'bobeirasa'

Users and Groups Users and groups are stored in /etc/passwd and /etc/group Each user name and group name is linked to a number (UID/GID) UID 0 = root 0-99 typically used for system/service accounts

File Permissions Three roles: user (file owner), group, other (“world”) Three permissions: read, write, execute Picture © Flickr user 'amagil'

root user root user = full access to everything on the system sudo, su – change user Don't use root user unless you have to! Comic:

Components of a process PID: Process ID number PPID: Parent PID UID & EUID: real & effective user ID GID & EGID: real & effective group ID Niceness Control terminal

Signals Sent to procs as communication Sent to terminal driver to kill, interrupt, or suspend Sent by admin to kill Sent by kernel Picture © Flickr user 'atomicshark'

Signals: Types you should know HUP, INT, QUIT, KILL, BUS, SIGV, TERM, STOP, TSTP, CONT, WINCH, USR1, USR2 Can catch, block, or dump core? BUS & SEGV – error signals KILL & STOP – cannot be blocked WINCH – term emulators

ps: monitor processes primary tool for monitoring processes differ between UNIX's show PID, UID, priority, control term, memory, status, etc complex over the years, archaic pstree

top: monitor in real-time “big picture” in real time refreshes every 2-3 seconds kill, renice, sort, memory, etc. htop – even better o color, prettier, more configurable Picture © United Artists from 'Hackers'