Ram disk creation on Linux

Ramdisks are very useful in the case of web servers for some heavily accessing contents.

The steps for crating Ramdisk is as follows,
Step 1: 

Edit the file /boot/grub/grub.cfg and add the entry "ramdisk_size={size in  KB}". For example if you need to crate 4GB of RAM disk, the entry should look like,


 ### BEGIN /etc/grub.d/10_linux ###
menuentry 'Ubuntu, with Linux 2.6.32-21-server' --class ubuntu --class gnu-linux --class gnu --class os {
    recordfail
    insmod ext2
    set root='(hd0,1)'
    search --no-floppy --fs-uuid --set ab3827ac-8003-4bed-81c0-9248d64362b0
    linux    /vmlinuz-2.6.32-21-server root=UUID=bbfccfa9-f878-4c42-83c1-0d82c3b2f44b ro quiet  ramdisk_size=4194304
    initrd    /initrd.img-2.6.32-21-server

Make sure the above entry made is in end of the linux kernel entry and it should be in a single line.

Once you done this, do a reboot and make the kernel read the parameter while next boot.

Step 2:

You can create the ramdisk using the following command,

      mkfs -q /dev/ram1 {size of ramdisk to me created in KB}

Create a folder to act as the mount point for above created ramdisk.

      mkdir -p /ramcache 

Mount the ramdisk to /ramcache

      mount /dev/ram1 /ramcache 

Following command will display the mounted partitions including the ramdisk.

      df -H 

Grub 2 Boot Order in Debian and Ubuntu servers

Grub2 is entirely different than the older version in terms of configuration and file system hierarchy. In the version 1 of Grub, changing the boot order can be accomplished by a single file editing. But in Grub2 which need to be done in another way, we are going to describe that here.

Here are the steps to follow:

1- To edit the grub file open terminal and type the following command :

    sudo gedit /etc/default/grub

You will got something like this :

GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”
GRUB_CMDLINE_LINUX=””
# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo’
#GRUB_GFXMODE=640×480
# Uncomment if you don’t want GRUB to pass “root=UUID=xxx” parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
# Uncomment to disable generation of recovery mode menu entrys
#GRUB_DISABLE_LINUX_RECOVERY=”true”

Now to change the boot order, you need to change the GRUB_DEFAULT Entry, for example you have  windows7 in the 3rd position and you want to set it as default,  edit the entry as below

       GRUB_DEFAULT=3

2- Now update Grub using the command:
 
       sudo update-grub 

Once you run the above command, the grub configuration files will get regenerated and in the file /boot/grub/grub.cfg, you can find an entry as set default = "3"