How to reduce horizontal ruler's width to the width of the document text in fancyhdr?

Question

I use fancyhdr to customize my footer. But this code:

\pagestyle{fancy}
\fancyhf{} % sets both header and footer to nothing
\lfoot{From: K. Grant}
\rfoot{\thepage}
\renewcommand{\footrulewidth}{0.4pt}

adds TWO rulers (top and bottom) with the width that is equal to the page width. I would like to reduce the width of the bottom ruler to the width of the main text and remove the top ruler. Plus, I would like the width of the text below the bottom ruler to be the same as the width of the main text. How to do this?

UPDATE: I forgot to mention that I also use geometry package to adjust page margins. Maybe this is the source of the problem?

UPDATE

\documentclass[12pt]{article}

\usepackage[utf8]{inputenc}
\usepackage{longtable}
\usepackage[top=2cm, bottom=2cm, left=1.5, right=1cm]{geometry}
\usepackage{fancyhdr}
\pagestyle{fancy}


\fancyhf{} % sets both header and footer to nothing
\lfoot{Page \thepage}
\rfoot{some text}
\renewcommand{\footrulewidth}{0.4pt}
\renewcommand{\headrulewidth}{0pt}

\begin{document}

SOME TEXT SOME TEXT SOME TEXT SOME TEXT  
SOME LOOOOONG TABLE

\end{document}

Answer 1

To disable the header rule, just add to your preamble

\renewcommand{\headrulewidth}{0.0pt}

Note that by default the start of a paragraph is indented, so it appears that the horizontal rule is longer than the text:

But, once you add some additional text (here I have used the \lipsum package to provide dummy text), you can see that width of the rule from fancyhdr is the full text width:

This code is a corrected version of your MWE, with additional dummy text:

\documentclass[12pt]{article}
\usepackage{lipsum}

\usepackage[utf8]{inputenc}
\usepackage{longtable}
\usepackage[top=2cm, bottom=2cm, left=1.5cm, right=1cm]{geometry}
\usepackage{fancyhdr}
\pagestyle{fancy}


\fancyhf{} % sets both header and footer to nothing
\lfoot{Page \thepage}
\rfoot{some text}
\renewcommand{\footrulewidth}{0.4pt}
\renewcommand{\headrulewidth}{0pt}

\begin{document}

SOME TEXT SOME TEXT SOME TEXT SOME TEXT  
SOME LOOOOONG TABLE
\lipsum

\end{document}

Answer 2

I suppose that you load package geometry after package fancyhdr. Change the order, otherwise you'll get wrong margins for the header/footer

Answer 3

In terms of removing the top (or header) rule, use

\renewcommand{\headrulewidth}{0pt}

This is what the output looks like in a minimal document:

\documentclass{article}
\usepackage[left=0.5in,right=1in]{geometry}% http://ctan.org/pkg/geometry
\usepackage{fancyhdr}% http://ctan.org/pkg/fancyhdr
\pagestyle{fancy}
\fancyhf{} % sets both header and footer to nothing
\lfoot{From: K. Grant}
\rfoot{\thepage}
\renewcommand{\headrulewidth}{0pt}% remove header rule
\renewcommand{\footrulewidth}{0.4pt}
\begin{document}
\null \vfill Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
Aenean faucibus auctor neque, quis vulputate purus facilisis et. 
\end{document}​

As you can see, the width of the footer (or header for that matter), including the rule, is the same as the text width (\textwidth), by default. As @Herbert suggests, you need to load geometry before you set any of the fanchdr settings. Here's what the output looks like if the order was reversed:

\documentclass{article}
\usepackage{fancyhdr}% http://ctan.org/pkg/fancyhdr
\pagestyle{fancy}
\fancyhf{} % sets both header and footer to nothing
\lfoot{From: K. Grant}
\rfoot{\thepage}
\renewcommand{\headrulewidth}{0pt}% remove header rule
\renewcommand{\footrulewidth}{0.4pt}
\usepackage[left=0.5in,right=1in]{geometry}% http://ctan.org/pkg/geometry
\begin{document}
\null \vfill Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
Aenean faucibus auctor neque, quis vulputate purus facilisis et. 
\end{document}​