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TRANSCRIPT
Introduction to the Linux Command Line
September 2012
Presented by Oralee Nudson ARSC User Consultant & Student Supervisor
Presentation Topics Information Assurance and
Security Awareness
Linux Overview
Navigating the File System
Connecting to Remote Systems
Working with Files
Working with Active Processes
Customize the User Environment
Feedback and Exercises
Information Assurance and Security Awareness
Download the ARSC Information Assurance pdf document or take the Information Systems Security Awareness course. Both are available here:
www.arsc.edu/arsc/support/policy/ia
Linux Overview Unix-like OS developed by Linus Torvalds in 1991
Open Source Software
“Runs on more computer hardware platforms than any other OS”
Run on Supercomputers, embedded systems
The shell is a command line interface to the OS Open a “terminal” window Edit files Check the status of running processes Send signals to processes
Navigating the File System Linux is a collection of
files and directories (think of folders)
The top directory is called the “root”.
Some directories contain actual files, others provide access to hardware devices
Commands: pwd
cd ls
ls –al ls $HOME mkdir
rmdir
Connecting to Remote Systems
Login with: ssh –X –Y [email protected]
Example: ssh –X –Y [email protected]
Copy files with: scp myfiles.tar.gz [email protected]:~/phys693/
Example: scp myfiles.tar.gz [email protected]:~/phys693
Use a GUI: filezilla, fetch, winscp
Working with Files Common Text Editors
vim or gvim
emacs nedit
Quickly view the contents of a file with: cat
less Exit with “q”
File Input/Output & Redirection
Three forms of input/output: “stdin” from keyboard or a file
“stdout” to screen or a file “stderr” to screen or a file
Redirect I/O with Alligators, “>” or “>>” or “<“
Pipes, “|”
Tie stdout and stderr together with “2>&1” mpirun $WORKDIR/wrf.exe > wrf.mix.out 2>&1 &!
File and Directory Permissions
Permissions control access to files and directories Three categories of access:
user group (type “groups” to determine which you belong to) other
Three categories of permissions: read write execute
Use “chmod” to modify access permissions chmod u+r myDir chmod g+rx myFile chmod go-rwx myFile
File and Directory Permissions
Security Awareness: World write permissions are discouraged.
ARSC Security policies on dot file permissions: http://www.arsc.edu/arsc/support/policy/secpolicy/index.xml#dot !
Working with Active Processes
“ps” allows you to view process statuses Useful variations “ps –elf” and “ps –aux”
“top” to view what’s eating up all the CPU resources! Exit with “q”
Send a signal: CTRL+c (kill) CTRL+z (suspend)
Search with “grep”, then “sort”
Common Linux Commands “kill” to terminate processes
% ./loop.sh & [1] 3039 % ps PID TTY TIME CMD 2779 pts/1 00:00:00 bash 3039 pts/1 00:00:00 loop.sh 3041 pts/1 00:00:00 sleep 3042 pts/1 00:00:00 ps % kill 3039 % ps PID TTY TIME CMD 2779 pts/1 00:00:00 bash 3055 pts/1 00:00:00 ps
The “&” puts the process in the background.
The process id for loop.sh is 3039.
The sleep process was started by loop.sh and will be killed when loop.sh is killed
The processes are gone
Kill process 3039.
Customizing the User Environment
Environment Variables store short strings of information
Important variables: $PATH, $HOME, $CENTER / $SCRATCH
The shell auto-expands variables
Set with bash: export CHUBBY_BUNNIES=funny! bash: export PATH=${PATH}:/u1/uaf/nudson/bin! csh/tcsh: setenv CHUBBY_BUNNIES funny! csh/tcsh: setenv PATH ${PATH}:/u1/uaf/nudson/bin!
View with echo $CHUBBY_BUNNIES
Customizing the User Environment
Important info about $PATH Its how the shell searches for executables, so you
don’t have to enter the command’s full path Order is important
“.” is intentionally left out for security purposes Use “./fun_script” to run local scripts, or list out the
entire path: /u1/uaf/nudson/fun_script
“env” lists all environment variables currently set
User Environment Customize your login by modifying your $HOME “.”
files http://www.arsc.edu/arsc/support/news/hpcnews/
hpcnews361/index.xml#article2 Example for bash users: Add the following to your ~/.profile file:
export PS1=“Good Morning!% ” Then source the file with “. ~/.profile”
Special Shell Characters
“*” matches anything
“?” matches a single character
“&” backgrounds a running process Bring process back to foreground with “fg” Try with CTRL+Z
Questions?
[email protected] (907) 450-8602
Evaluation Form:
http://www.arsc.edu/arsc/support/training/trainingevalform/index.xml
Exercises
http://people.arsc.edu/~bahls/classes/exer.tar.gz