stsadmin -o deploysolution shows access denied error for some files

Problem

After firing deploysolution, looking at system settings > farm solutions and the error looks something like "Can not overrite xxxx file, access is denied".

Cause

specified file in your error is read only in your web application directory. Most of the time this happens when you are using some source control system that is making the file read only when it is checked in. 

Solution

Go to properties of the file and uncheck read only. If you are running a farm and you got multiple application servers, you need to repeate this for each application server.

Conclusion

80% of the developers uses command line to deploy their wsp as it is the convinient way to add or upgraded the solution.

Finally...

Got the same error? Don't worry try above solution. Didn't worked? Let me know which one worked for you?