the messages says: error=30, msg=Read-only file system
If you would try to write to a directory where you don't have permission, the error message would show:
error=13, msg=Permission denied
For example, try dump model database to the root filesystem "/model.dmp"
(Assuming here that you don't run your Sybase server with root account)
Check the output from command: mount
Anyway, the touch command would be easiest way to test