Use this bass for the whole the whole song:
     G    D    Am    G    D    C
G-|---------------|---------------|
D-|---------------|---------------|
A-|----2--0----0--|----2--0-------|
E-|--3-------3----|--3-------3p0--|

G  320003
D  200232
Am 002210
C  332010

Intro:
|G  |D  |Am |
|G  |D  |C  |

Verse 1:
G        D              Am
Mama take this badge offa me
G      D          C
I cant use it any more
G          D                Am
Its gettin dark, to dark to see
G                 D             C
Feels like knockin on heavens door

Chorus:
G           D                  Am
Knock knock knockin on heavens door
G           D                  C
Knock knock knockin on heavens door
G           D                  Am
Knock knock knockin on heavens door
G           D                  C
Knock knock knockin on heavens door

Verse 2:
G       D               Am
Mama put my guns to the ground
G      D             C
I cant shoot them anymore
G              D              Am
That long dark cloud is comin down
G              D              C
I Feel like knockin on heavens door

Chorus:
G           D                  Am
Knock knock knockin on heavens door
G           D                  C
Knock knock knockin on heavens door
G           D                  Am
Knock knock knockin on heavens door
G           D                  C
Knock knock knockin on heavens door

Outro:
|G  |D  |Am |
|G  |D  |C  |
|G  |D  |Am |
|G  |D  |C  |
I hope this is correct cos its my first time