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To change maximum processes per user

1. open /etc/security/limits.conf as root user

2. Write the following lines at the bottom of the page.

   Code Block
   <Username> hard nproc unlimited <Username> soft nproc unlimited

   Note
   Replace <Username> with original user name.

3. Restart the machine.

To change maximum file handles per user

1. open /etc/security/limits.conf as root user

2. Write the following lines at the bottom of the page.

   Code Block
   <Username> hard nofile unlimited <Username> soft nofile unlimited

   Note
   Replace <Username> with original user name.

3. Restart the machine.

Checking the Swap Size

# free -k

The command free is used to know how much swap space is currently used by the system. It displays the memory details in KB.

Following is a sample output resulting from free -k command:

		      total	   used      free	shared	buffers	  cached
Mem:		3082356	2043700   1038656	  	 0	  50976	 1646268
-/+ buffers/cache: 	 346456   2735900
Swap:		4192956       0	  4192956 

# swapon -s

Swapon command with option -s displays the current swap size in KB and the file name.

Following is a sample output resulting from swapon -s command:

	 Filename			    Type           Size   		  Used 		   Priority
    /dev/sda2    	  partition    	   4192956 				0    		    -1 

# cat /proc/swaps

This command is same as the swapon -s command, which gives the same output:

	 Filename			    Type           Size   		  Used 		   Priority
    /dev/sda2    	  partition    	   4192956 				0    		    -1 

Increasing the swap size

Additional Swap Space can be created using a:

1. Hard Drive
2. File

Both the methods are explained in the below sections.

Using a Hard Drive Partition

If you have an additional hard disk (or space available in an existing disk), create a partition using fdisk command.

Assume that the partition created is: /dev/sdc1 and perform the following actions:

1. Setup this newly created partition as swap area using the mkswap command:

   # mkswap /dev/sdc1
    

2. Enable the swap partition for usage using swapon command:

   # swapon /dev/sdc1
    

3. Add the following line to the /etc/fstab file to make the swap space partition available even after the reboot:
   # cat /etc/fstab

   Code Block
   /dev/sdc1 swap swap defaults 0 0

4. Verify whether the newly created swap area is available for your requirement using swapon and free commands:

   # swapon -s 

   Code Block
   title Sample Output for # swapon -s command
   Filename Type Size Used Priority /dev/sda2 partition 4192956 0 -1 /dev/sdc1 partition 1048568 0 -2

   Note
   In the output of swapon -s command, the Type column will say "partition" if the swap space is created from a disk partition.

   # free -k

   Code Block
   title Sample Output for # free -k command
   total used free shared buffers cached Mem: 3082356 3022364 59992 0 55056 2645472 -/+ buffers/cache: 323836 2758520 Swap: 5241524 0 5241524

Using a File

If you do not have any additional disks, create a file somewhere on your file system and use that file for swap space.

1. Create a swap file with the name "myswapfile" under /root  directory with a size of 1024MB (1GB) using the following dd command:
   # dd if=/dev/zero of=/root/myswapfile bs=1M count=1024

   Code Block
   1024+0 records in 1024+0 records out

2. Check the user permissions set in the file using the following command:
   # ls -l /root/myswapfile

   Code Block
   -rw-r--r-- 1 root root 1073741824 Aug 14 23:47 /root/myswapfile

3. Create Root Permission, that is, change the permission of the swap file so that only root can access it.
   # chmod 600 /root/myswapfile
 

4. Make this file as a swap file using mkswap command:
   # mkswap /root/myswapfile

   Code Block
   title mkswap command output
   Setting up swapspace version 1, size = 1073737 kB

5. Enable the newly created swapfile.
   # swapon /root/myswapfile
 

6. To make this swap file available as a swap area even after the reboot, add the following line to the /etc/fstab file using command:
   # cat /etc/fstab

   Code Block
   /dev/sdc1 swap swap defaults 0 0

7. Verify whether the newly created swap area is available for your requirement using swapon and free commands:

   # swapon -s 

   Code Block
   title Sample Output for # swapon -s command
   Filename Type Size Used Priority /dev/sda2 partition 4192956 0 -1 /dev/sdc1 partition 1048568 0 -2

   Note
   In the output of swapon -s command, the Type column will say "file" if the swap space is created from a swap file.

   # free -k

   Code Block
   title Sample Output for # free -k command
   total used free shared buffers cached Mem: 3082356 3022364 59992 0 55056 2645472 -/+ buffers/cache: 323836 2758520 Swap: 5241524 0 5241524