Common SSH Commands or Linux Shell Commands

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

chmod: changes file access permissions
The set of 3 go in this order from left to right:

0 = — No permission
1 = –X Execute only
2 = -W- Write only
3 = -WX Write and execute
4 = R– Read only
5 = R-X Read and execute
6 = RW- Read and write
7 = RWX Read, write and execute

chmod numberpermissions filename

chmod 000 : No one can access
chmod 644: Usually for HTML pages
chmod 755: Usually for CGI scripts

chown: changes file ownership permissions
The set of 2 go in this order from left to right:

chown root myfile.txt : Changes the owner of the file to root
chown root.root myfile.txt : Changes the owner and group of the file to root

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 Spaceto 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.

File Editing with VI ssh commands
vi : another editor, tons of features, harder to use at first than pico
vi /home/burst/public_html/index.html : edit the index page for the user’s website.
Whie in the vi program you can use the following useful commands, you will need to hit SHIFT + : to go into command mode

:q! : This force quits the file without saving and exits vi
:w : This writes the file to disk, saves it
:wq : This saves the file to disk and exists vi
:LINENUMBER : EG :25 : Takes you to line 25 within the file
:$ : Takes you to the last line of the file
:0 : Takes you to the first line of the file

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

ln : create’s “links” between files and directories
ln -s /usr/local/apache/conf/httpd.conf /etc/httpd.conf : Now you can edit /etc/httpd.conf rather than the original. changes will affect the orginal, however you can delete the link and it will not delete the original.

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.
who : This also shows who is on the server in an shell.

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.
top then type Shift + M to sort by memory usage or 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!

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/

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.
cp -av * ../newdir : Copies all files and directories recurrsively in the current directory INTO newdir

mv : Move a file command
mv oldfilename newfilename : Move a file or directory from oldfilename to newfilename

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!!!

TAR: Creating and Extracting .tar.gz and .tar files
tar -zxvf file.tar.gz : Extracts the file
tar -xvf file.tar : Extracts the file
tar -cf archive.tar contents/ : Takes everything from contents/ and puts it into archive.tar
gzip -d filename.gz : Decompress the file, extract it

ZIP Files: Extracting .zip files shell command

Firewall – iptables commands
iptables -I INPUT -s IPADDRESSHERE -j DROP : This command stops any connections from the IP address
iptables -L : List all rules in iptables
iptables -F : Flushes all iptables rules (clears the firewall)
iptables –save : Saves the currenty ruleset in memory to disk
service iptables restart : Restarts iptables

Apache Shell Commands
httpd -v : Outputs the build date and version of the Apache server.
httpd -l : Lists compiled in Apache modules
httpd status : Only works if mod_status is enabled and shows a page of active connections
service httpd restart : Restarted Apache web server

MySQL Shell Commands
mysqladmin processlist : Shows active mysql connections and queries
mysqladmin drop databasenamehere : Drops/deletes the selected database
mysqladmin create databasenamehere : Creates a mysql database

Restore MySQL Database Shell Command
mysql -u username -p password databasename < databasefile.sql : Restores a MySQL database from databasefile.sql Backup MySQL Database Shell Command mysqldump -u username -p password databasename > databasefile.sql : Backup MySQL database to databasefile.sql

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)

PID TTY TIME COMMAND 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

#top (untuk monitoring penggunaan resource secara live)
#top -D1 (interval setiap 1 detik, bisa diganti sesuai selera -D2, -D3 dst..)
#top kemudian pencet angka 1 (masih sama tetapi resource CPU lebih detail)

#yum install mc -y (untuk install MC = midnight commander, mirip total commander di windows, sejenis file manager versi console untuk centos, redhat)
#mc (menjalankan MC yang sudah diinstall)

#swapoff -a kemudian lanjutkan dengan #swapon -a (mengembalikan swap file ke angka 0 )

#sync; echo 3 > /proc/sys/vm/drop_caches (refresh RAM / menghilangkan cache yang ada di dalam RAM)

#mysqlcheck -Aao –auto-repair (optimizing database sql, auto repair jika ada yang error)

How to install mcrypt for PHP in ubuntu

apt-get install php5-mcrypt
/etc/init.d/apache2 restart

Sometimes you might get the message “php5-mcrypt is already the newest version“. If so, install with:

apt-cache search php5-m
php5-mapscript – php5-cgi module for MapServer
php5-mcrypt – MCrypt module for php5
php5-memcache – memcache extension module for PHP5
php5-ming – Ming module for php5
php5-mhash – MHASH module for php5
php5-mysql – MySQL module for php5
php5-sybase – Sybase / MS SQL Server module for php5

apt-get –reinstall install php5-mcrypt
/etc/init.d/apache2 restart

Nginx + Php-fpm + Varnish Cache + WordPress

10 Million hits per day with WordPress on a $15 virtual server

Install Ubuntu 11.10 (Oneiric) on a new virtual private server- it needs to be 11.10 for all the packages that I’m going to list to work out of the box, but it’s all possible to do with other distributions.

I used Amazon EC2 to build my test server, but Linode are also very good.

For the purpose of the documentation, my server details were as follows, yours will be different:

Public DNS Name:
Public IP Address:

Login to the server and become root

login as ubuntu via ssh, then run the sudo -i command to become root

ssh [email protected]
sudo -i

Configure a firewall first

Since we’re going to be installing various network services which by default listen on all interfaces, it’s important to configure a firewall.

For Ubuntu, this is nice and easy, simply use the ufw package.

Execute the following commands to configure it:

ufw allow ssh
ufw allow http
ufw logging off
ufw enable

Once this is done, your server has a relatively secure firewall, though it’s worth looking at fail2ban to prevent brute force password attacks.

If you’re using Amazon EC2, you’ll also need to open the Security Group to allow traffic on port 80. You can do this using the AWS Security Groups Console, you might need to change the region. Select the security group you used when you started the instance, and then click “Inbound”, then select “HTTP” from the drop down menu, then finally click “Add Rule”. You don’t need to restart the instance for it to take effect.

Install and Configure MySQL

apt-get update
apt-get install mysql-server

When prompted, set a mysql “root” user password

mysql -u root -p

When prompted, enter your newly set root password

At the mysql> prompt, run the following 4 commands, replacing ENTER_A_PASSWORD with a password of your own


That’s MySQL installed, ready for the PHP and Web server installation (nginx).

Install and configure PHP

We need to install not just PHP, but the PHP FPM system, APC, and the MySQL module

apt-get install php5-fpm php-pear php5-common php5-mysql php-apc php5-gd

Edit /etc/php5/fpm/php.ini and add these lines at the bottom:

apc.write_lock = 1
apc.slam_defense = 0

Edit /etc/php5/fpm/pool.d/www.conf


listen =


listen = /dev/shm/php-fpm-www.sock

Below that, insert these 3 lines

listen.owner = nginx = nginx
listen.mode = 0660

Then, further down in the same file, replace these 2 lines

user = www-data
group = www-data


user = nginx
group = nginx

Save the file, PHP FPM is now complete, but it won’t work until we install nginx, so don’t worry about starting it now.

Install and Configure Nginx

Instructions based on the Nginx website.

Download the nginx secure key to verify the package

cd /tmp/
apt-key add /tmp/nginx_signing.key

Add the sources to the APT sources file by running these 2 commands (the >> is important!)

echo “deb lucid nginx” >> /etc/apt/sources.list
echo “deb-src lucid nginx” >> /etc/apt/sources.list

Download and install nginx by running

apt-get update
apt-get install nginx

When that completes, nginx will be installed, but needs configuring for WordPress.

nginx configuration files are in /etc/nginx

First, edit /etc/nginx/nginx.conf

Inside the http section , insert the following line so that when you later add varnish in front, things don’t break all over the place:

port_in_redirect off;

Next, cd to /etc/nginx/conf.d and create a new file, /etc/nginx/conf.d/drop with the contents of the drop file from GitHub

Then, replace /etc/nginx/conf.d/default.conf with the contents of the github default.conf file changing all entries for with your own domain name (there’s 3 entries, including 1 near the bottom)

Make a directory, /var/www/ and set the ownership:

mkdir -p /var/www/
chown nginx:nginx /var/www/
chmod 775 /var/www

That’s nginx configured, restart it and the PHP FPM service by running:

service nginx restart
service php5-fpm restart

Now, you’re actually ready to install WordPress!

This is pretty simple, run:

cd /tmp
tar zxvf latest.tar.gz
cd wordpress
mv * /var/www/
chown -R nginx:nginx /var/www

To configure WordPress, run:

cp /var/www/wp-config-sample.php /var/www/wp-config.php
chown nginx:nginx /var/www/wp-config.php

In a web browser, visit and copy the results

Edit /var/www/wp-config.php

and scroll down to fine the AUTH_KEY line down to NONCE_SALT, and replace them with the values you copied from the site

Then, replace the default values with the MySQL ones you chose earlier (not the root user):

define(‘DB_NAME’, ‘database_name_here’);
define(‘DB_USER’, ‘username_here’);
define(‘DB_PASSWORD’, ‘password_here’);

And once it’s done, if you’ve not had any errors and your domain name is pointing at the right IP (this is important!), then you’ll be able to visit your domain and see the WordPress configuration page at

Go through install questions, choose a sensible username and password (it’s highly recommended you change the admin user from “admin” to something else.

Go to settings then select permalinks, and choose “Custom Structure”, and paste in the value below (including the % symbols)


Then hit “Save Changes”

It’s time to create a test post, so click on “Posts” then “Add New”

Enter a title and body, then hit “Post”, and make a note of it’s friendly URL.

Run a test to see how we’re doing

100 users, 60 seconds. Timeouts, low hit rates, errors, etc. CPU flat out, seems to be the initial bottleneck.

This rush generated 632 successful hits in 1.0 min and we transferred 1.76 MB of data in and out of your app. The average hit rate of 9.81/second translates to about 847,776 hits/day.

You got bigger problems though: 34.91% of the users during this rush experienced timeouts or errors!

So the server is running, but it’s still too slow!

Next, we will enable the WordPress caching systems

Go to the wordpress admin page, then plugins, and click install new plugin.

Update Skip the W3 Total Cache plugin if you’re following this as a tutorial, it’s not been updated in ages. I’ll update this post in the future with W3 Super Cache instructions instead, but everything else should work as it is for now
Search for “W3 Total Cache”, then click “Install Now” when the search results return. When installation is complete, click “Activate Plugin”.

Go to the new “Performance” section in the menu at the left side of the page.

Scroll through the cache options, selecting “PHP APC” at each opportunity and enabling the following 2 sections:

Database Cache
Object Cache

Hit “Save All Settings” then hit “Deploy”

Rerun the test again, performance should be much improved

This rush generated 2,902 successful hits in 1.0 min and we transferred 27.59 MB of data in and out of your app. The average hit rate of 46/second translates to about 4,006,008 hits/day.

If we then up the run from 100 users to 250 users, there are still problems we need to fix:

This rush generated 4,733 successful hits in 1.0 min and we transferred 36.20 MB of data in and out of your app. The average hit rate of 72/second translates to about 6,297,653 hits/day.

You got bigger problems though: 5.49% of the users during this rush experienced timeouts or errors!

You can see the Blitz results from the Nginx And APC configuration in this PDF.

So still not perfect – Time to install varnish 3!

apt-get install varnish

Edit /etc/varnish/default.vcl replace the contents with the file default.vcl file from github.

Edit /etc/default/varnish

Change the section

DAEMON_OPTS=”-a :6081 \
-T localhost:6082 \
-f /etc/varnish/default.vcl \
-S /etc/varnish/secret \
-s malloc,256m”


DAEMON_OPTS=”-a :80 \
-T localhost:6082 \
-f /etc/varnish/default.vcl \
-S /etc/varnish/secret \
-s malloc,64m”

Next, we need to edit the nginx configuration to listen on port 8080, instead of port 80 – Varnish is going to be running on port 80 instead.

Edit /etc/nginx/conf.d/default.conf and replace

listen 80;


listen 8080;

Save the file, then run

service nginx restart
service varnish restart

Re-run the test with 100 users

Almost no CPU usage, should get perfect results

This rush generated 2,959 successful hits in 1.0 min and we transferred 28.36 MB of data in and out of your app. The average hit rate of 47/second translates to about 4,093,000 hits/day.

Re-run the blitz with 250 users

This rush generated 7,342 successful hits in 1.0 min and we transferred 70.38 MB of data in and out of your app. The average hit rate of 117/second translates to about 10,134,627 hits/day.

You can see the full final run blitz performance details in this PDF.

There it is, 10 million hits per day using WordPress on a box costing less than $20 a month, all thanks to varnish and nginx, easy!

Restart Nginx WebServer

How do I restart nginx web server under Linux?

To restart nginx web server use any one of the following command as a root user:
# /etc/init.d/nginx restart
However, recommed way is as follows which should work with any Linux distribution :
# nginx -s reload
# /usr/local/nginx/sbin/nginx -s reload