kAFS: AFS FILESYSTEM ==================== ABOUT ===== This filesystem provides a fairly simple AFS filesystem driver. It is under development and only provides very basic facilities. It does not yet support the following AFS features: (*) Write support. (*) Communications security. (*) Local caching. (*) pioctl() system call. (*) Automatic mounting of embedded mountpoints. USAGE ===== When inserting the driver modules the root cell must be specified along with a list of volume location server IP addresses: insmod rxrpc.o insmod kafs.o rootcell=cambridge.redhat.com:172.16.18.73:172.16.18.91 The first module is a driver for the RxRPC remote operation protocol, and the second is the actual filesystem driver for the AFS filesystem. Once the module has been loaded, more modules can be added by the following procedure: echo add grand.central.org 18.7.14.88:128.2.191.224 >/proc/fs/afs/cells Where the parameters to the "add" command are the name of a cell and a list of volume location servers within that cell. Filesystems can be mounted anywhere by commands similar to the following: mount -t afs "%cambridge.redhat.com:root.afs." /afs mount -t afs "#cambridge.redhat.com:root.cell." /afs/cambridge mount -t afs "#root.afs." /afs mount -t afs "#root.cell." /afs/cambridge NB: When using this on Linux 2.4, the mount command has to be different, since the filesystem doesn't have access to the device name argument: mount -t afs none /afs -ovol="#root.afs." Where the initial character is either a hash or a percent symbol depending on whether you definitely want a R/W volume (hash) or whether you'd prefer a R/O volume, but are willing to use a R/W volume instead (percent). The name of the volume can be suffixes with ".backup" or ".readonly" to specify connection to only volumes of those types. The name of the cell is optional, and if not given during a mount, then the named volume will be looked up in the cell specified during insmod. Additional cells can be added through /proc (see later section). MOUNTPOINTS =========== AFS has a concept of mountpoints. These are specially formatted symbolic links (of the same form as the "device name" passed to mount). kAFS presents these to the user as directories that have special properties: (*) They cannot be listed. Running a program like "ls" on them will incur an EREMOTE error (Object is remote). (*) Other objects can't be looked up inside of them. This also incurs an EREMOTE error. (*) They can be queried with the readlink() system call, which will return the name of the mountpoint to which they point. The "readlink" program will also work. (*) They can be mounted on (which symbolic links can't). PROC FILESYSTEM =============== The rxrpc module creates a number of files in various places in the /proc filesystem: (*) Firstly, some information files are made available in a directory called "/proc/net/rxrpc/". These list the extant transport endpoint, peer, connection and call records. (*) Secondly, some control files are made available in a directory called "/proc/sys/rxrpc/". Currently, all these files can be used for is to turn on various levels of tracing. The AFS modules creates a "/proc/fs/afs/" directory and populates it: (*) A "cells" file that lists cells currently known to the afs module. (*) A directory per cell that contains files that list volume location servers, volumes, and active servers known within that cell. THE CELL DATABASE ================= The filesystem maintains an internal database of all the cells it knows and the IP addresses of the volume location servers for those cells. The cell to which the computer belongs is added to the database when insmod is performed by the "rootcell=" argument. Further cells can be added by commands similar to the following: echo add CELLNAME VLADDR[:VLADDR][:VLADDR]... >/proc/fs/afs/cells echo add grand.central.org 18.7.14.88:128.2.191.224 >/proc/fs/afs/cells No other cell database operations are available at this time. EXAMPLES ======== Here's what I use to test this. Some of the names and IP addresses are local to my internal DNS. My "root.afs" partition has a mount point within it for some public volumes volumes. insmod -S /tmp/rxrpc.o insmod -S /tmp/kafs.o rootcell=cambridge.redhat.com:172.16.18.73:172.16.18.91 mount -t afs \%root.afs. /afs mount -t afs \%cambridge.redhat.com:root.cell. /afs/cambridge.redhat.com/ echo add grand.central.org 18.7.14.88:128.2.191.224 > /proc/fs/afs/cells mount -t afs "#grand.central.org:root.cell." /afs/grand.central.org/ mount -t afs "#grand.central.org:root.archive." /afs/grand.central.org/archive mount -t afs "#grand.central.org:root.contrib." /afs/grand.central.org/contrib mount -t afs "#grand.central.org:root.doc." /afs/grand.central.org/doc mount -t afs "#grand.central.org:root.project." /afs/grand.central.org/project mount -t afs "#grand.central.org:root.service." /afs/grand.central.org/service mount -t afs "#grand.central.org:root.software." /afs/grand.central.org/software mount -t afs "#grand.central.org:root.user." /afs/grand.central.org/user umount /afs/grand.central.org/user umount /afs/grand.central.org/software umount /afs/grand.central.org/service umount /afs/grand.central.org/project umount /afs/grand.central.org/doc umount /afs/grand.central.org/contrib umount /afs/grand.central.org/archive umount /afs/grand.central.org umount /afs/cambridge.redhat.com umount /afs rmmod kafs rmmod rxrpc