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= Basic Architecture =

Using the shared filesystem involves a combination of Kerberos and OpenAFS.

= File conventions =

The `/afs` tree contains shared filesystems. `/afs/hcoop.net` (symlinked from `/afs/hcoop` as well) is our piece of the AFS-o-sphere. Subdirectories include:

 * `/afs/hcoop.net/user`, the home of home directories
 * `/afs/hcoop.net/user/U/US/$USERNAME`, `$USERNAME`'s home directory
 * `/afs/hcoop.net/common/etc`, the home of non-platform-specific fun stuff like DomTool

= Connecting to AFS from an HCoop server =

I found this handy summary of the commands that must be run:
  http://www.eos.ncsu.edu/remoteaccess/LinuxOpenAfs/kreset_debian/kreset

On our servers, it seems sufficient to run:
{{{kinit
aklog}}}

These should be run automatically if you log in normally, but admins `sudo`ing around to different users seem to need to run `aklog` manually to access AFS.

= The kadmin shell =

All Kerberos administration commands are run from a special shell, called Kadmin. There are two variants of Kadmin:
kadmin is the usual, remote version of the command which can be run on any machine; kadmin.local is the "local"
version which can only be ran on the AFS fileserver (deleuze).

Invoke kadmin.local as `sudo kadmin.local -p YOURUSERNAME_admin`. It is good to include "-p YOURUSERNAME_admin", or
kadmin will "authenticate" as the first user it finds in the ticket cache, which may or may not be the username you
expected. All the administrative commands would work anyway (since you ran kadmin.local), but an incorrect principal
name would make various statistics incorrect (like name of principal who was adding/changing entries in the DB).

To invoke kadmin, use `kadmin -p YOURUSERNAME_admin`. In normal course of action, kadmin asks for a password. This is
impractical for automated scripts. As usual, instead of a password, you can also pass a keytab file. Our keytabs are
saved in /etc/keytabs/ on each system, and they are readable by group 'wheel'. So administrators should be able
to invoke 'kadmin' (use control shell) or kinit/k5start (impersonate any user) by supplying target user's key from
a keytab, such as `kadmin -p domtool/deleuze -k -t /etc/keytabs/domtool.deleuze` .

= Creating a new user =

We follow the convention that Kerberos users for daemons are named `$DAEMON`, where `$DAEMON` is the name of the daemon (for instance, the name of system user it runs as, or the name of its `/etc/init.d` file). ''Some daemons
currently use DAEMON/HOST scheme, but this will be changed later and is not to be used for any new principals
you create''.

To add the Kerberos principal for a daemon, run this in kadmin:{{{
addprinc -randkey -policy service $DAEMON}}}

AFS users exist separately from Kerberos principals. To add the AFS user for a daemon to which you want to assign UID `$UID`, run:{{{
pts createuser $DAEMON}}}

"keytab" files smooth the way to running daemons that run with AFS privileges. An access-protected local file contains a user's credentials, and daemons read these files on starting up in order to authenticate.

To create a keytab for a daemon, run this in kadmin:{{{
ktadd -k /etc/keytabs/$DAEMON -e "des3-hmac-sha1:normal rc4-hmac:normal" $DAEMON
chown $DAEMON:wheel /etc/keytabs/$DAEMON
chmod 440 /etc/keytabs/$DAEMON
}}}
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AndrewFileSystem (last edited 2018-11-15 03:45:21 by ClintonEbadi)