fatal: Not a valid object name: 'master'

I have a private server running git 1.7 When I

git init 

a folder it doesn't create a master branch. Cause when i do:

git branch 

it doesn't list anything. When I do:

git --bare init

it creates the files. When I type

git branch master 

it says:

fatal: Not a valid object name: 'master'.

When I git init a folder it doesn't create a master branch

This is true, and expected behaviour. Git will not create a master branch until you commit something.

When I do git --bare init it creates the files.

A non-bare git init will also create the same files, in a hidden .git directory in the root of your project.

When I type git branch master it says "fatal: Not a valid object name: 'master'"

That is again correct behaviour. Until you commit, there is no master branch.

You haven't asked a question, but I'll answer the question I assumed you mean to ask. Add one or more files to your directory, and git add them to prepare a commit. Then git commit to create your initial commit and master branch.

Git creates a master branch once you've done your first commit. There's nothing to have a branch for if there's no code in the repository.