Hi,

I need encrypt root file system. I used below command

cryptsetup -y -v luksFormat /dev/sda1

But i am getting below error.

WARNING!
========
This will overwrite data on /dev/sda1 irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase:
Verify passphrase:
[ 94.408069] alg: No test for fips(ansi_cprng) (fips_ansi_cprng)
Cannot format device /dev/md126p2 which is still in use.
Command failed with code 16: Device or resource busy

Could anyone please help me how to encrypt root file system in linux system.

Thanks,

There are tons of guides out there with step by step instructions for setting up encryption. I'd recommend you google for one. This error makes it look like your /dev/sda is mounted and it shouldn't be

I have got tons of links but those are not for root file system encryption. Could you share the link for this? I know that we have to umount the file system to encrypt but for root file system umount is possible?

Use a liveCD/USB to do it. Encrypting the root is not as straightforward as a data partition as the initrd has to be rebuilt with the cryptsetup included. That is very distro specific.
Of course you will lose everything on that partition as the message warns.

Have a look at this