Trying to append /proc/cmdline

Using vim, I add what I need to the end of the line. Since it's read only, I exit with :wq! which gives me:

"/proc/cmdline" E667 Fsync failed
WARNING: Original file may be lost or damaged don't quit the editor until the file is successfully written!
Press ENTER or type command to continue

If I press enter, I see the line appended and the process starts all over with same results. If I just try to quit, with :!q I am able to, but the file reverts back to what it was.

Has anyone encountered this problem before? Or can write-only files simply not be changed? BTW, I am root when doing all this.

If I am mistaken, please correct me, but aren't files in /proc dynamic (i.e. created and used by the OS and therefore not manually editable)? I'm not sure what you're trying to accomplish by editing /proc/cmdline. Perhaps if you shared your goal with us, we could find an alternate solution?

That is it. You are exactly right. It will be appended when I boot and edit the command line.