OpenAFS for Debian
Introduction
For an OpenAFS client system, install openafs-client and a kernel
module. See README.modules for information on how to build the kernel
module for your system. Then, read /etc/openafs/afs.conf to understand
the client configuration options. The openafs-client package will
attempt to guess at a good cache configuration based on the size of your
cache, but you may want to tune it further. There are also other
options configured in that file you may want to consider.
The AFS client cache must be on an ext2 or ext3 partition. Other file
systems often do not support the semantics required by the AFS kernel
module and will cause afsd to abort (to avoid kernel panics). In
particular, XFS, ReiserFS, and tmpfs will NOT work. If you are using
one of those file systems and don't have a spare partition for a
separate file system for the cache, you need to use the -memcache option
to afsd (although this is not always stable) or create a large file with
dd, create an ext2 file system in it with mkfs, and then mount it with
mount -o loop for use as a cache partition.
FAM does not work correctly with AFS except for directories that are
world-readable since it does not run in the user's security context and
therefore doesn't have the user's AFS tokens. If you are using FAM,
you'll encounter errors from file managers such as Nautilus that use it
if you browse restricted AFS directories. Instead of FAM, install
gamin, which runs in the user's security context and works correctly
with AFS.
For information on how to set up an OpenAFS server, read README.servers.
You will want the openafs-fileserver package for a file server and,
additionally, the openafs-dbserver package for a database server.
Documentation
For the complete OpenAFS manual, install openafs-doc. This is the same
documentation as found at , and is
unfortunately outdated in several respects, but it's the best that we
have at present.
If want to set up a new cell, read README.servers and then look at the
example session in configuration-transcript.txt.gz in this directory.
The procedure outlined in these two files is much simpler and more
secure than the one in the OpenAFS documentation, but the OpenAFS
documentation provides useful background.
Build Options
The OpenAFS servers have been built with --enable-supergroups, which
permits nesting of PTS groups. Be aware that the PT database created by
these packages is not compatible with servers not built with
--enable-supergroups if nested PTS groups are used. In other words, if
you need the openafs-dbserver package to interoperate with ptservers
that aren't built with this option, don't use this capability.
bosserver is built with --enable-bos-new-config. If
/etc/openafs/BosConfig.new exists when bosserver starts, it will be
renamed to /etc/openafs/BosConfig before the configuration file is
read. This allows queuing of changes to the configuration that will
take effect at the next restart.
Changes Relative to Stock OpenAFS
Long-time AFS users may be confused by the directory layout. The files
that normally go in /usr/vice/etc go in /etc/openafs. The cache should
be mounted on /var/cache/openafs. The server files have been moved
around even more; see README.servers for the details.
The OpenAFS kernel module is named openafs, not libafs, to better match
normal Linux kernel module naming standards. The Debian source package
only builds one kernel module that matches the kernel source tree it is
built against and does not attempt to build separate SMP and non-SMP
modules against the same tree. Doing so does not work on all platforms.
To distinguish between an SMP and a non-SMP kernel module package, use
--append_to_version; see README.modules for more information.
The OpenAFS servers have been patched to support listing up to four
realms in /etc/openafs/server/krb.conf. Any realms listed in that file
(all on one line, space-separated) will be treated as local for
authorization decisions (in other words, the relam will be stripped off
and the unqualified principal name checked against AFS ACLs, UserList,
PTS groups, and so forth). The default OpenAFS server only supports
listing one realm in this file.
The AFS up utility is installed as afs-up, since the standard name is
rather generic.
The libopenafs-dev package only includes static libraries and there are
no shared library packages. The shared libraries built by AFS are not
compatible with Debian policy. They do not have a stable ABI or an
appropriate SONAME.
kaserver is not included. New AFS cells should use Kerberos v5 rather
than the old K4-based kaserver KDC.
The OpenAFS PAM modules have been built with pthreads rather than the
standard LWP AFS libraries for compatibility with a threaded sshd.
Debugging and Bug Reporting
The current OpenAFS installation process installs fileserver and
volserver unstripped, since backtraces and other debugging information
for those binaries are necessary to track down file server problems.
For the Debian packages, the fileserver and volserver binaries in the
openafs-fileserver package are stripped, but the debugging information
is available in the openafs-dbg package, which can be installed
separately. If it is installed, gdb will find that debugging
information automatically.
Eventually the openafs-dbg package will contain debugging information
for all OpenAFS binaries. This is pending upstream changes to the stock
OpenAFS installation rules.
When reporting a bug in the OpenAFS client, please include your exact
kernel version and architecture (reportbug will do this for you). Also,
if the client caused a kernel oops or BUG, be sure to include the
complete kernel output, including the lines before the oops. That's
where the OpenAFS error message, if any, will be.
When reporting a bug in the OpenAFS file server, please include
backtrace information from a core dump, if any. If the file server is
deadlocked, you can capture a core dump using the gcore script that
comes with the gdb package. The file server is threaded, so use the
command "thread apply all backtrace" in gdb to get a complete backtrace.
It's also often useful to have the output of rxdebug 7000 at
the time of the problem and the FileLog from the file server. You can
increase the logging level of the file server with kill -TSTP (and reset
it to 0 with kill -HUP).
You can report any bug in OpenAFS against the Debian package with
reportbug and the OpenAFS package maintainers will forward the bug
upstream as necessary. If you do want to report a bug directly
upstream, see http://www.openafs.org/ for bug reporting instructions.
PAM Authentication
Any new OpenAFS cell is strongly encouraged to use Kerberos v5 for
authentication. If you want PAM to automatically obtain AFS credentials
and you are using Kerberos v5, you will want to install the libpam-krb5
and libpam-openafs-session packages and then put something like the
following in /etc/pam.d/common-auth:
auth [success=ok default=1] pam_krb5.so ignore_root
auth [default=done] pam_openafs_session.so
auth required pam_unix.so nullok_secure try_first_pass
and something like the following in /etc/pam.d/common-session:
session optional pam_krb5.so ignore_root
session optional pam_openafs_session.so
session required pam_unix.so
You'll probably also want the following in /etc/pam.d/common-account:
account required pam_krb5.so ignore_root
account required pam_unix.so
There are, of course, many variations depending on what different
mechanism you want to use and how you want to handle fallbacks.
If you are still using Kerberos v4 and the OpenAFS kaserver (or a KDC
that understands the same protocol) for authentication, you can instead
use the libpam-openafs-kaserver package and a configuration like:
auth sufficient pam_afs.so ignore_root
auth required pam_unix.so nullok_secure try_first_pass
in /etc/pam.d/common-auth and:
session optional pam_afs.so
session required pam_unix.so
in /etc/pam.d/common-session. Use pam_afs.krb.so instead of pam_afs.so
if you also want the PAM module to acquire a ticket cache for you. If
using this configuration with sshd, you may need to disable privilege
separation to get everything working properly. I've had mixed results
with that. Obviously, converting to Kerberos v5 authentication is
strongly preferred.
If you are using the kaserver as your KDC, you may also want to install
the openafs-kpasswd package to get the administrative utilities for
managing those Kerberos accounts.
-- Russ Allbery , Mon, 17 Dec 2007 18:29:42 -0800