Common SSH or Linux Shell Commands – JustHost

ls : list files/directories in a directory, comparable to dir in windows/dos.
ls -al : shows all files (including ones that start with a period), directories, and details attributes for each file.

cd : change directory
cd /usr/local/apache : go to /usr/local/apache/ directory
cd ~ : go to your home directory
cd – : go to the last directory you were in
cd .. : go up a directory

cat : print file contents to the screen
cat filename.txt : cat the contents of filename.txt to your screen

tail : like cat, but only reads the end of the file
tail /var/log/messages : see the last 20 (by default) lines of /var/log/messages
tail -f /var/log/messages : watch the file continuously, while it’s being updated
tail -200 /var/log/messages : print the last 200 lines of the file to the screen

more : like cat, but opens the file one screen at a time rather than all at once
more /etc/userdomains : browse through the userdomains file.
hit Space to go to the next page, q to quit

pico : friendly, easy to use file editor
pico /home/burst/public_html/index.html : edit the index page for the user’s website.

vi : another editor, tons of features
vi /home/burst/public_html/index.html : edit the index page for the user’s website.

grep : looks for patterns in files
grep root /etc/passwd : shows all matches of root in /etc/passwd
grep -v root /etc/passwd : shows all lines that do not match root

touch : create an empty file
touch /home/burst/public_html/404.html : create an empty file called 404.html in the directory /home/burst/public_html/

ln : create’s “links” between files and directories
ln -s /home/username/tmp/webalizer webstats: Now you can display to show your webalizer stats online. You can delete the symlink (webstats) and it will not delete the original stats on the server.

rm : delete a file
rm filename.txt : deletes filename.txt, will more than likely ask if you really want to delete it
rm -f filename.txt : deletes filename.txt, will not ask for confirmation before deleting.
rm -rf tmp/ : recursively deletes the directory tmp, and all files in it, including subdirectories. BE VERY CAREFULL WITH THIS COMMAND!!!

last : shows who logged in and when
last -20 : shows only the last 20 logins
last -20 -a : shows last 20 logins, with the hostname in the last field

w : shows who is currently logged in and where they are logged in from.

netstat : shows all current network connections.
netstat -an : shows all connections to the server, the source and destination ips and ports.
netstat -rn : shows routing table for all ips bound to the server.

top : shows live system processes in a nice table, memory information, uptime and other useful info. 
This is excellent for managing your system processes, resources and ensure everything is working fine and your server isn’t bogged down.
Shift + M to sort by memory usage
Shift + P to sort by CPU usage

ps: ps is short for process status, which is similar to the top command. It’s used to show currently running processes and their PID.
A process ID is a unique number that identifies a process, with that you can kill or terminate a running program on your server (see kill command).
ps U username : shows processes for a certain user
ps aux : shows all system processes
ps aux –forest : shows all system processes like the above but organizes in a hierarchy that’s very useful!

file : attempts to guess what type of file a file is by looking at it’s content.
file * : prints out a list of all files/directories in a directory

du : shows disk usage.
du -sh : shows a summary, in human-readble form, of total disk space used in the current directory, including subdirectories.
du -sh * : same thing, but for each file and directory. helpful when finding large files taking up space.

wc : word count
wc -l filename.txt : tells how many lines are in filename.txt

cp : copy a file
cp filename filename.backup : copies filename to filename.backup
cp -a /home/burst/new_design/* /home/burst/public_html/ : copies all files, retaining permissions form one directory to another.
find * -type d|xargs -i cp –verbose php.ini {} : copies your php.ini file into all directories recursively.

kill: terminate a system process
kill -9 PID EG: kill -9 431
kill PID EG: kill 10550
Use top or ps ux to get system PIDs (Process IDs)


10550 pts/3 0:01 /bin/csh
10574 pts/4 0:02 /bin/csh
10590 pts/4 0:09 APP

Each line represents one process, with a process being loosely defined as a running instance of a program. The column headed PID (process ID) shows the assigned process numbers of the processes. The heading COMMAND shows the location of the executed process.

Putting commands together
Often you will find you need to use different commands on the same line. Here are some examples. Note that the | character is called a pipe, it takes date from one program and pipes it to another.
means create a new file, overwriting any content already there.
>> means tp append data to a file, creating a newone if it doesn not already exist.
send input from a file back into a command.

grep User /usr/local/apache/conf/httpd.conf |more
This will dump all lines that match User from the httpd.conf, then print the results to your screen one page at a time.

last -a > /root/lastlogins.tmp
This will print all the current login history to a file called lastlogins.tmp in /root/

tail -10000 /var/log/exim_mainlog |grep |more
This will grab the last 10,000 lines from /var/log/exim_mainlog, find all occurances of
(the period represents ‘anything’, comment it out with a so it will be interpretted literally), then send it to your screen page by page.

netstat -an |grep :80 |wc -l
Show how many active connections there are to apache (httpd runs on port 80)

mysqladmin processlist |wc -l
Show how many current open connections there are to mysql

mysqldump -u username -p dbname > file.sql
MySQL Dump

mysql -u username -p database_name <file.sql
Importing MySQL database

tar -zxvf file.tar.gz
UnTAR file

Finding path to

Show all installed packages or software in Linux, FreeBSD, OpenBSD

Show all installed packages or software in Linux, FreeBSD, OpenBSD.

Q. I am using CentOS how do I show all installed packages in Linux?

A. You need to use rpm command to display all installed packages in Linux.

Red Hat/Fedora Core/CentOS Linux

Type the following command to get list of all installed software

# rpm -qa | less



Debian Linux

Type the following command to get list of all installed software:

# dpkg --get-selections



Ubuntu Linux

Type the following command to get list of all installed software:

# sudo dpkg --get-selections




Type the following command to get list of all installed software:

# pkg_info | less
# pkg_info apache



Use pkg_version command to summarizes the versions of all installed packages:

# pkg_version | less
# pkg_version | grep 'lsof'




OpenBSD also use pkg_info command to display list of all installed packages or software:

# pkg_info | less
# pkg_info apache


Possible update counterCache Function

I haven’t tested this yet. But it is a possible update counterCache function.



function counterCheck( )



$counterTemplate =

“UPDATE :atable AS :amodel

SET :counter = (


FROM :table AS :model

WHERE :model.:foreignkey =



$updates = array();


$models = Configure::listObjects(‘model’) ;


foreach ($models as $model) {


$mainTable = Inflector::tableize($model);

if (!empty($this->$model->belongsTo)) {

foreach ($this->$model->belongsTo as $assocModel =>

$def) {

if (isset($def[‘counterCache’]) &&

$def[‘counterCache’]) {

$assocTable =


$assocClass = $def[‘className’];

$foreignKey = $def[‘foreignKey’];

$counter = strtolower($model) . ‘_count’;

$query = String::insert($counterTemplate,


‘table’ => $mainTable,

‘model’ => $model,

‘atable’ => $assocTable,

‘amodel’ => $assocModel,

‘foreignkey’ => $foreignKey,

‘counter’ => $counter


$result = $this->Configuration->query($query);

$affectedRows = $this->Configuration-


$updates[] = array(

‘query’ => $query,

‘affected_rows’ => $affectedRows







$this->set(‘updates’, $updates);





service httpd restart

If you notice the server starting to thrash, as root you can type “service httpd restart” and Apache will be restarted freeing all the memory it has consumed.  However, but the time it has reached this point, it is hard to log in and run any commands.

FlowingData: How to Make an Interactive Network Visualization

I have looked at d3 network visualization demos / tutorials before. I always tell myself I will do it. But I need to get on this. Link below is to a tutorial on flowing data.

Concepts in Programming Languages – University of Cambridge Course

The following are all copy and pasted from a University of Cambridge course link to the website below. It was accessible by public, so I figured I should dump it here. Maybe I can read some of this when I have a vacation.

Lecture slides

  • Introduction and motivation.
    Additional reading material:
  • K. ZusePlankalkul.
  • The first procedural language: FORTRAN (1954-58).
    Additional reading material:
  • Fortran.
  • The first declarative language: LISP (1958-62).
    Additional reading material:
  • J. McCarthyRecursive functions of symbolic expressions and their computation by machine.
    Communications of the ACM, 3(4):184-195, 1960.
  • Block-structured procedural languages: Algol (1958-68) and Pascal (1970).
    AppendixBCPL (1967) and C (1971-78)
    Additional reading material:
  • D. E. KnuthThe remaining trouble spots in ALGOL 60.
    Communications of the ACM, Volume 10, Issue 10, pages 611-618, 1967.
  • B. KerninghanWhy Pascal is not my favorite programming language.
    AT&T Bell Laboratories. Computing Science Technical Report No. 100, 1981.
  • Object-oriented languages — Concepts and origins: SIMULA (1964-67) and Smalltalk (1971-80).
    SML codeObjects in SML!?
    Programming languageSqueak.
    Additional reading material:
  • A. C. KayThe early history of Smalltalk.
    ACM SIGPLAN Notices, Volume 28, No. 3, 1993.
  • P. WegnerConcepts and Paradigms of Object-Oriented Programming
    Expansion of OOPSLA-89 Keynote Talk.
  • B. StroustrupWhat is Object-Oriented Programming? (1991 revised version).
    Proc. 1st European Software Festival. February, 1991.
  • Types in programming languages: ML (1973-1978).
    Additional reading material:
  • A. Koenig. An anecdote about ML type inference.
    USENIX Symp. on Very High Level Languages, 1994.
  • Data abstraction and modularity: SML Modules (1984-97).
    Additional reading material:
  • M. TofteFour Lectures on Standard ML.
    LFCS Report Series ECS-LFCS-89-73, 1989.
  • The state of the art: Scala (2004-2006).
    Programming languageScala.
    Additional reading material:
  • M. Odersky et alAn overview of the Scala programming language.
    Technical Report LAMP-REPORT-2006-001, Second Edition, 2006.
  • M. Odersky et alA Tour of the Scala Programming Language.
    Programming Methods Laboratory, EPFL, 2007.
  • M. OderskyScala By Example.
    Programming Methods Laboratory, EPFL, 2008.
  • Books

  • Main:
  • M. ScottProgramming Language Pragmatics (2nd edition).
    Morgan Kaufmann, 2006.
  • J.C. MitchellConcepts in programming languages.
    Cambridge University Press, 2003.
  • T.W.Pratt and M.V.ZelkowitzProgramming Languages: Design and implementation (3rd edition).
    Prentice Hall, 1999.
  • Other:
  • R. L. Wexelblat (ed.). History of Programming Languages.
    ACM Monograph Series, 1981.
  • N. Metropolis, J. Howlett, G.-C. Rota (eds.). A History of Computing in the Twentieth Century: A Colletion of Essays.
    Academic Press, 1980.
  • T.J. Bergin and R. G. Gibson (eds.). History of programming languages – II.
    ACM Press, 1996.
  • [Actual Course Website]

    Lightweight Directory Access Protocol

    I need to learn to use LDAP for an upcoming project, so I will start to keep some notes here. A lot of this post will be copy and pasted and Wikipedia and other sources.

    A client starts LDAP session by connection to an LDAP server, called a Directory System Agent (DSA).
    The default port is TCP port 389. The client sends an operation request to server and server responds. Client can start sending more requests before responses, however the server may send responses in any oreder.

    Protocal Overview: 

    • StartTLS — use the LDAPv3 Transport Layer Security (TLS) extension for a secure connection
    • Bind — authenticate and specify LDAP protocol version
    • Search — search for and/or retrieve directory entries
    • Compare — test if a named entry contains a given attribute value
    • Add a new entry
    • Delete an entry
    • Modify an entry
    • Modify Distinguished Name (DN) — move or rename an entry
    • Abandon — abort a previous request
    • Extended Operation — generic operation used to define other operations
    • Unbind — close the connection (not the inverse of Bind)

    Directory Structure

    • A entry in the Directory can contain a set of attributes
    • An attribute has a name and possibly multiple values — the attributes are defined in a schema 
    • Each entry has a unique identifier: its Distinguished Name (DN). This consists of its Relative Distinguished Name (RDN), constructed from some attribute(s) in the entry, followed by the parent entry’s DN. Think of the DN as the full file path and the RDN as its relative filename in its parent folder (e.g. if /foo/bar/myfile.txt were the DN, then myfile.txt would be the RDN).


    The option I am most interested in currently is

    Bind (authenticate)

    The Bind operation establishes the authentication state for a connection.

    Simple Bind can send the user’s DN and password in plaintext, so the connection should be protected usingTransport Layer Security (TLS). The server typically checks the password against the userPassword attribute in the named entry.

    Anonymous Bind (with empty DN and password) resets the connection to anonymous state.

    SASL (Simple Authentication and Security Layer) Bind provides authentication services through a wide range of mechanisms, e.g. Kerberos or the client certificate sent with TLS.

    Bind also sets the LDAP protocol version. The version is an integer and at present must be either 2 (two) or 3 (three), although the standard supports integers between 1 and 127 (inclusive) in the protocol. If the client requests a version that the server does not support, the server must set the result code in the bind response to the code for a protocol error. Normally clients should use LDAPv3, which is the default in the protocol but not always in LDAP libraries.

    Bind had to be the first operation in a session in LDAPv2, but is not required in LDAPv3 (the current LDAP version).

    [wiki link]

    Other links for my reading on this:


    LDAP tutorial


    Installed a few scripts

    So I installed a few things I wanted to play with using simple scripts. Simple scripts is an option available on my cpanel that allowed to me add scripts where I want and set up an admin account for them.

    I added the following

    A survey script  using limesurveys,

    A project management script using phpprojekt,

    and A forum script using phpbb

    It offers a ton of options but unless you read the users manual a lot of it doesnt make sense, also its not very intuitive.

    I can’t figure out how to make other users… seriously. I spent like a good 30 seconds looking, I shouldn’t need to spend more. But the options it has looks very cool.

    EDIT: I found it like a minute after I wrote this — I had to Google it. It tells you how in their wiki…

    I have used it before, I know its solid.

    I will probably write more on the scripts above once I get a chance to play with them more.

    It’s all about the SCRUM Master hat.

    This is a great video that explains scrum development. It is something I want to use personally when my current programming team gets a little bigger.

    This following is the introduction to Scrum Development on Wikipedia:

    Scrum is an iterative, incremental framework for project management often seen in agile software development, a type of software engineering.

    Although the Scrum approach was originally suggested for managing product development projects, its use has focused on the management of software development projects, and it can be used to run software maintenance teams or as a general project/program management approach.