Changing default keytab name problem

[Illia Baidakov]

Hello, Kerberos!

I wish to change default name and location of keytab file.
When I run kadmin and type "ktadd -k /some/where/krb5.keytab
primary/instance at REALM", the command has success.
But when I add "default_keytab_name = /some/where/krb5.keytab" relation to
[libdefaults] section of /etc/krb5.conf file, the command "ktadd
primary/instance at REALM" returns the error message "kadmin: Cannot write to
specified key table while adding key to keytab".
The target directory has 755-mode permissions.
Without adding default_kaytab_name relation the latter command creates
/etc/krb5.keytab file successfully.

What is the best way to get my aim?

Thanks in advance
Illia Baidakov.