Thank You very much for replying. Yes it is there in /etc/group, this is the output -
serveradmin@openserver:~$ cat /etc/group | grep serveradmin
root:x:0:serveradmin,nexussalary,library
adm:x:4:ebox,serveradmin,nexussalary
dialout:x:20:serveradmin,asterisk
cdrom:x:24:serveradmin,ebox
www-data:x:33:serveradmin
plugdev:x:46:serveradmin
serveradmin:x:1000:nexussalary,library
lpadmin:x:117:serveradmin,ebox
sambashare:x:118:serveradmin
admin:x:119:serveradmin,domainadmin
libvirtd:x:129:serveradmin
I already tried with pwconv, but that blocked the user,"serveradmin", from accessing the zentyal web interface. Now, I am no more able to login to zentyal web interface using this username.