BSDCan_2007_010

Adam is an undergraduate Computer Science and Applied Mathematics student at Stony Brook University, New York. He is currently working with Professor Erez Zadok, at the Filesystem and Storage Laboratory, on FreeBSD related projects, particularly AutoFS. Filesystems store, organize, and retrieve data for users and often these files are stored on remote machines, or removable media. The UNIX system requires that these filesystems must be mounted before files can be accessed. In network environments, mounted filesystems can result in extra traffic, even when the filesystem is mounted, but no files are used. This extra traffic is undesirable, and adversely affects the available network bandwidth, and mounted filesystems require more in-kernel memory and datastructures to maintain them as "active." Nobody wants to keep remote filesystems mounted, when they're not in use. AutoFS works with AMD, a daemon which auto-mounts filesystems, to provide an on-demand mounting facility. The purpose of AutoFS is to limit the load upon AMD, and to provide a layer of kernel control over mounting. This control is used to minimise the number of calls to the Automounting daemon (AMD) thereby providing better performance as a user navigates the "unified" filesystem tree. This paper describes the implementation details of AutoFS for FreeBSD 6.x