whmapi1 is a command line tool in cpanel server, that can be used for many WHM API call.

To get WHM access to an account using root SSH, run

whmapi1 create_user_session user=root service=whostmgrd locale=en

Getting Cpanel Access from root SSH

whmapi1 create_user_session user=USERNAME service=cpaneld locale=en

Replace USERNAME with your user name.

Example

[root@server78 ~]# whmapi1 create_user_session user=hoston service=cpaneld locale=en
--- 
data: 
  cp_security_token: /cpsess2861136544
  expires: '1490648623'
  locale: en
  service: cpaneld
  session: hoston:eizCyj88xF0Bp0t2:create_user_session,2a323820e26953b958038712601c43b5
  url: https://server78.hostonnet.com:2083/cpsess2877136544/login/?locale=en&session=hoston%3aeizCyj66xF0Bp0t2%3acreate_user_session%2c2a44420e269588958038712601c43b5
metadata: 
  command: create_user_session
  reason: Created session
  result: 1
  version: 1
[root@server78 ~]#