| 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 |