The errno for "Read-only file system". This error will be returned by various operations, such as open (with write access set), link, unlink, mkdir, creat, etc. on a file system with one of two properties:
- The mount is specified as read-only.
- The file system does not support write operations. This includes many synthetic file systems, such as procfs, fdescfs, and kernfs. In these file systems, typically, opening some files for write access is okay, but manual modification of the file system's layout/contents is not.