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- ====================
- kAFS: AFS FILESYSTEM
- ====================
-
-Contents:
-
- - Overview.
- - Usage.
- - Mountpoints.
- - Proc filesystem.
- - The cell database.
- - Security.
- - Examples.
-
-
-========
-OVERVIEW
-========
-
-This filesystem provides a fairly simple secure AFS filesystem driver. It is
-under development and does not yet provide the full feature set. The features
-it does support include:
-
- (*) Security (currently only AFS kaserver and KerberosIV tickets).
-
- (*) File reading and writing.
-
- (*) Automounting.
-
- (*) Local caching (via fscache).
-
-It does not yet support the following AFS features:
-
- (*) pioctl() system call.
-
-
-===========
-COMPILATION
-===========
-
-The filesystem should be enabled by turning on the kernel configuration
-options:
-
- CONFIG_AF_RXRPC - The RxRPC protocol transport
- CONFIG_RXKAD - The RxRPC Kerberos security handler
- CONFIG_AFS - The AFS filesystem
-
-Additionally, the following can be turned on to aid debugging:
-
- CONFIG_AF_RXRPC_DEBUG - Permit AF_RXRPC debugging to be enabled
- CONFIG_AFS_DEBUG - Permit AFS debugging to be enabled
-
-They permit the debugging messages to be turned on dynamically by manipulating
-the masks in the following files:
-
- /sys/module/af_rxrpc/parameters/debug
- /sys/module/kafs/parameters/debug
-
-
-=====
-USAGE
-=====
-
-When inserting the driver modules the root cell must be specified along with a
-list of volume location server IP addresses:
-
- modprobe af_rxrpc
- modprobe rxkad
- modprobe kafs rootcell=cambridge.redhat.com:172.16.18.73:172.16.18.91
-
-The first module is the AF_RXRPC network protocol driver. This provides the
-RxRPC remote operation protocol and may also be accessed from userspace. See:
-
- Documentation/networking/rxrpc.txt
-
-The second module is the kerberos RxRPC security driver, and the third module
-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 18.9.48.14:128.2.203.61:130.237.48.87 >/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, with the latter separated by colons.
-
-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
-
-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 modprobe.
-
-Additional cells can be added through /proc (see later section).
-
-
-===========
-MOUNTPOINTS
-===========
-
-AFS has a concept of mountpoints. In AFS terms, 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 a follow-link capability
-(ie: symbolic link semantics). If anyone attempts to access them, they will
-automatically cause the target volume to be mounted (if possible) on that site.
-
-Automatically mounted filesystems will be automatically unmounted approximately
-twenty minutes after they were last used. Alternatively they can be unmounted
-directly with the umount() system call.
-
-Manually unmounting an AFS volume will cause any idle submounts upon it to be
-culled first. If all are culled, then the requested volume will also be
-unmounted, otherwise error EBUSY will be returned.
-
-This can be used by the administrator to attempt to unmount the whole AFS tree
-mounted on /afs in one go by doing:
-
- umount /afs
-
-
-===============
-PROC FILESYSTEM
-===============
-
-The AFS modules creates a "/proc/fs/afs/" directory and populates it:
-
- (*) A "cells" file that lists cells currently known to the afs module and
- their usage counts:
-
- [root@andromeda ~]# cat /proc/fs/afs/cells
- USE NAME
- 3 cambridge.redhat.com
-
- (*) A directory per cell that contains files that list volume location
- servers, volumes, and active servers known within that cell.
-
- [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/servers
- USE ADDR STATE
- 4 172.16.18.91 0
- [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/vlservers
- ADDRESS
- 172.16.18.91
- [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/volumes
- USE STT VLID[0] VLID[1] VLID[2] NAME
- 1 Val 20000000 20000001 20000002 root.afs
-
-
-=================
-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 system belongs is added to the database when modprobe is performed by the
-"rootcell=" argument or, if compiled in, using a "kafs.rootcell=" argument on
-the kernel command line.
-
-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 18.9.48.14:128.2.203.61:130.237.48.87 >/proc/fs/afs/cells
-
-No other cell database operations are available at this time.
-
-
-========
-SECURITY
-========
-
-Secure operations are initiated by acquiring a key using the klog program. A
-very primitive klog program is available at:
-
- http://people.redhat.com/~dhowells/rxrpc/klog.c
-
-This should be compiled by:
-
- make klog LDLIBS="-lcrypto -lcrypt -lkrb4 -lkeyutils"
-
-And then run as:
-
- ./klog
-
-Assuming it's successful, this adds a key of type RxRPC, named for the service
-and cell, eg: "afs@<cellname>". This can be viewed with the keyctl program or
-by cat'ing /proc/keys:
-
- [root@andromeda ~]# keyctl show
- Session Keyring
- -3 --alswrv 0 0 keyring: _ses.3268
- 2 --alswrv 0 0 \_ keyring: _uid.0
- 111416553 --als--v 0 0 \_ rxrpc: afs@CAMBRIDGE.REDHAT.COM
-
-Currently the username, realm, password and proposed ticket lifetime are
-compiled in to the program.
-
-It is not required to acquire a key before using AFS facilities, but if one is
-not acquired then all operations will be governed by the anonymous user parts
-of the ACLs.
-
-If a key is acquired, then all AFS operations, including mounts and automounts,
-made by a possessor of that key will be secured with that key.
-
-If a file is opened with a particular key and then the file descriptor is
-passed to a process that doesn't have that key (perhaps over an AF_UNIX
-socket), then the operations on the file will be made with key that was used to
-open the file.
-
-
-========
-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 /tmp/rxrpc.o
-insmod /tmp/rxkad.o
-insmod /tmp/kafs.o rootcell=cambridge.redhat.com: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 18.9.48.14:128.2.203.61:130.237.48.87 > /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
-rmmod kafs
-rmmod rxkad
-rmmod rxrpc