How do I change a read only file in Linux?

chmod a=r foldername to give only read permission for everyone.
…
The command for changing directory permissions for group owners is similar, but add a “g” for group or “o” for users:

1. chmod g+w filename.
2. chmod g-wx filename.
3. chmod o+w filename.
4. chmod o-rwx foldername.

How do you edit a read only file?

Read-only Files

1. Open Windows Explorer and navigate to the file you want to edit.
2. Right-click the file name and select “Properties.”
3. Select the “General” tab and clear the “Read-only” check box to remove the read-only attribute or select the check the box to set it.