Create Swap file on Linux

Create swap file

You will need to choose a location for your file. In this tutorial, it will be stored at the root of the server. We will create a 2GB swap file by running the following command:

dd if=/dev/zero of=/swapfile count=2048 bs=1M

The dd command will produce output in a similar format to:

2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 10.5356 s, 204 MB/s

Next, verify that the file is located at the root of your Vultr VPS by running:

ls / | grep swapfile

Proceed if you see the swapfile file.

 

Activate the swap file

Swap files are not recognized automatically. We will need to tell the server how to format the file and enable it so it can be used as a valid swap file. As a security measure, update the swapfile permissions to only allow R/W for root and no other users. Run:

chmod 600 /swapfile

The permission change can be verified by running the following command:

ls -lh /swapfile

You will see a file display:

-rw------- 1 root root 2.0G Oct  2 18:47 /swapfile

Next, tell the server to setup the swap file by running:

mkswap /swapfile

After running it, you will see the following output:

Setting up swapspace version 1, size = 2097148 KiB
no label, UUID=ff3fc469-9c4b-4913-b653-ec53d6460d0e

If everything is shown as above, you are now ready to move on to the next step.

Turn swap on

Once your file is ready to be used as swap, you need to enable it by running:

swapon /swapfile

You can verify that the swap file is active by running the free command again.

free -m

total       used       free     shared    buffers     cached
Mem:          1840       1754         86         16         23       1519
-/+ buffers/cache:        210       1630
Swap:         2047          0       2047

If Swap shows something other than 0, then you have successfully setup swap.

Enable swap on reboot

By default, your server will not automatically enable this new swap file. To enable it on boot, you can update the /etc/fstab file. Any text editor will suffice. In this example, I will be using nano.

nano /etc/fstab

Add the following line at the end of the file:

/swapfile   none    swap    sw    0   0

Save and close when you are finished editing the file. We are all done!

Install Ruby on Rails on CentOS

Install Ruby

 yum install ruby

install Ruby dependancies.

yum install gcc g++ make automake autoconf curl-devel openssl-devel zlib-devel httpd-devel apr-devel apr-util-devel sqlite-devel
yum install ruby-rdoc ruby-devel

Install Ruby Gems

yum install rubygems

Install Rails

gem update
 gem update --system

then install rails

gem install rails

for check version try

gem install rails -V

Apache and Node.js on the same Ubuntu server

Install Node.js

apt-get install nodejs
apt-get install npm
 apt-get install build-essential

Install express node module

npm install express

Edit Apache

sudo a2enmod proxy
sudo a2enmod proxy_http
edit the  default apache conf
ProxyRequests Off
<Proxy *>
 Order deny,allow
 Allow from all
 </Proxy>
 <Location /node>
 ProxyPassReverse  http://server-name:5000
 </Location>
Now restart the apache 
service apache2 restart
The first app
created two files: web.js and package.json
web.js:
varexpress = require("express");
varapp = express();
app.use(express.logger());
app.get('/', function(request, response) {
    response.send('Hello World!');
});
app.get('/test', function(request, response) {
    response.send('This was only a test');
});
app.use(function(err, req, res, next){
  console.error(err.stack);
  res.send(500, 'Something broke!');
});
varport = process.env.PORT || 8080;
app.listen(port, function() {
    console.log("Listening on "+ port);
});
package.json:
{
  "name": "node-example",
  "version": "0.0.1",
  "dependencies": {
    "express": "3.1.x"
  },
  "engines": {
    "node": "0.10.x",
    "npm": "1.2.x"
  }
}
Start the app
    node web.js