Managing Linux System-level Configuration

While using Linux/Unix OS, there are various configurations that may be changed to optimize the availability of resources to Fiorano. Below sections discuss the various configuration options.

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.

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   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.

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   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:

# 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:

# cat /proc/swaps

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

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

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

   # swapon -s 

   Sample Output for # swapon -s command
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   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

   Sample Output for # free -k command

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

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

   mkswap command output
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

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

   # swapon -s 

   Sample Output for # swapon -s command
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   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

   Sample Output for # free -k command