[Koha] Unable install SUDO

[takan bhatt]

Sir/Madam

I have installed Debian Xfce in Virtual Box also added non-free repository
in sources.list. Then updated and upgraded with apt-get. but updation is
not going smoothly. then after I am unable to install Sudo and this is
necessary step in koha installation. I think this is probably problem with
repository.

Kindly help me which repositories are required ?

Rajesh Bhatt