Linux Files Immutable?
Ever feel 'operattion not-permitted' on linux, please do this to revert or even if you want to protect a file to be safe.
Execution
cat ~/.ssh/id_rsa.pub > authorized_keys
chattr +i authorized_keys
rm authorized_keys
rm: remove write-protected regular file `file1'? y
rm: cannot remove `file1': Operation not permitted
To revert to previous state
chattr -i authorized_keys