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0795e7c0 | 1 | ==================== |
1da177e4 LT |
2 | kAFS: AFS FILESYSTEM |
3 | ==================== | |
4 | ||
0795e7c0 DH |
5 | Contents: |
6 | ||
7 | - Overview. | |
8 | - Usage. | |
9 | - Mountpoints. | |
10 | - Proc filesystem. | |
11 | - The cell database. | |
12 | - Security. | |
13 | - Examples. | |
14 | ||
15 | ||
16 | ======== | |
17 | OVERVIEW | |
18 | ======== | |
1da177e4 | 19 | |
0795e7c0 DH |
20 | This filesystem provides a fairly simple secure AFS filesystem driver. It is |
21 | under development and does not yet provide the full feature set. The features | |
22 | it does support include: | |
1da177e4 | 23 | |
0795e7c0 | 24 | (*) Security (currently only AFS kaserver and KerberosIV tickets). |
1da177e4 | 25 | |
0795e7c0 | 26 | (*) File reading. |
1da177e4 | 27 | |
0795e7c0 DH |
28 | (*) Automounting. |
29 | ||
30 | It does not yet support the following AFS features: | |
31 | ||
32 | (*) Write support. | |
33 | ||
34 | (*) Local caching. | |
35 | ||
36 | (*) pioctl() system call. | |
37 | ||
38 | ||
39 | =========== | |
40 | COMPILATION | |
41 | =========== | |
42 | ||
43 | The filesystem should be enabled by turning on the kernel configuration | |
44 | options: | |
45 | ||
46 | CONFIG_AF_RXRPC - The RxRPC protocol transport | |
47 | CONFIG_RXKAD - The RxRPC Kerberos security handler | |
48 | CONFIG_AFS - The AFS filesystem | |
49 | ||
50 | Additionally, the following can be turned on to aid debugging: | |
51 | ||
52 | CONFIG_AF_RXRPC_DEBUG - Permit AF_RXRPC debugging to be enabled | |
53 | CONFIG_AFS_DEBUG - Permit AFS debugging to be enabled | |
54 | ||
55 | They permit the debugging messages to be turned on dynamically by manipulating | |
56 | the masks in the following files: | |
57 | ||
58 | /sys/module/af_rxrpc/parameters/debug | |
59 | /sys/module/afs/parameters/debug | |
60 | ||
61 | ||
62 | ===== | |
1da177e4 LT |
63 | USAGE |
64 | ===== | |
65 | ||
66 | When inserting the driver modules the root cell must be specified along with a | |
67 | list of volume location server IP addresses: | |
68 | ||
0795e7c0 DH |
69 | insmod af_rxrpc.o |
70 | insmod rxkad.o | |
1da177e4 LT |
71 | insmod kafs.o rootcell=cambridge.redhat.com:172.16.18.73:172.16.18.91 |
72 | ||
0795e7c0 DH |
73 | The first module is the AF_RXRPC network protocol driver. This provides the |
74 | RxRPC remote operation protocol and may also be accessed from userspace. See: | |
75 | ||
76 | Documentation/networking/rxrpc.txt | |
77 | ||
78 | The second module is the kerberos RxRPC security driver, and the third module | |
79 | is the actual filesystem driver for the AFS filesystem. | |
1da177e4 LT |
80 | |
81 | Once the module has been loaded, more modules can be added by the following | |
82 | procedure: | |
83 | ||
84 | echo add grand.central.org 18.7.14.88:128.2.191.224 >/proc/fs/afs/cells | |
85 | ||
86 | Where the parameters to the "add" command are the name of a cell and a list of | |
0795e7c0 | 87 | volume location servers within that cell, with the latter separated by colons. |
1da177e4 LT |
88 | |
89 | Filesystems can be mounted anywhere by commands similar to the following: | |
90 | ||
91 | mount -t afs "%cambridge.redhat.com:root.afs." /afs | |
92 | mount -t afs "#cambridge.redhat.com:root.cell." /afs/cambridge | |
93 | mount -t afs "#root.afs." /afs | |
94 | mount -t afs "#root.cell." /afs/cambridge | |
95 | ||
1da177e4 LT |
96 | Where the initial character is either a hash or a percent symbol depending on |
97 | whether you definitely want a R/W volume (hash) or whether you'd prefer a R/O | |
98 | volume, but are willing to use a R/W volume instead (percent). | |
99 | ||
100 | The name of the volume can be suffixes with ".backup" or ".readonly" to | |
101 | specify connection to only volumes of those types. | |
102 | ||
103 | The name of the cell is optional, and if not given during a mount, then the | |
104 | named volume will be looked up in the cell specified during insmod. | |
105 | ||
106 | Additional cells can be added through /proc (see later section). | |
107 | ||
108 | ||
0795e7c0 | 109 | =========== |
1da177e4 LT |
110 | MOUNTPOINTS |
111 | =========== | |
112 | ||
0795e7c0 DH |
113 | AFS has a concept of mountpoints. In AFS terms, these are specially formatted |
114 | symbolic links (of the same form as the "device name" passed to mount). kAFS | |
115 | presents these to the user as directories that have a follow-link capability | |
116 | (ie: symbolic link semantics). If anyone attempts to access them, they will | |
117 | automatically cause the target volume to be mounted (if possible) on that site. | |
1da177e4 | 118 | |
0795e7c0 DH |
119 | Automatically mounted filesystems will be automatically unmounted approximately |
120 | twenty minutes after they were last used. Alternatively they can be unmounted | |
121 | directly with the umount() system call. | |
1da177e4 | 122 | |
0795e7c0 DH |
123 | Manually unmounting an AFS volume will cause any idle submounts upon it to be |
124 | culled first. If all are culled, then the requested volume will also be | |
125 | unmounted, otherwise error EBUSY will be returned. | |
1da177e4 | 126 | |
0795e7c0 DH |
127 | This can be used by the administrator to attempt to unmount the whole AFS tree |
128 | mounted on /afs in one go by doing: | |
1da177e4 | 129 | |
0795e7c0 | 130 | umount /afs |
1da177e4 LT |
131 | |
132 | ||
0795e7c0 | 133 | =============== |
1da177e4 LT |
134 | PROC FILESYSTEM |
135 | =============== | |
136 | ||
1da177e4 LT |
137 | The AFS modules creates a "/proc/fs/afs/" directory and populates it: |
138 | ||
0795e7c0 DH |
139 | (*) A "cells" file that lists cells currently known to the afs module and |
140 | their usage counts: | |
141 | ||
142 | [root@andromeda ~]# cat /proc/fs/afs/cells | |
143 | USE NAME | |
144 | 3 cambridge.redhat.com | |
1da177e4 LT |
145 | |
146 | (*) A directory per cell that contains files that list volume location | |
147 | servers, volumes, and active servers known within that cell. | |
148 | ||
0795e7c0 DH |
149 | [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/servers |
150 | USE ADDR STATE | |
151 | 4 172.16.18.91 0 | |
152 | [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/vlservers | |
153 | ADDRESS | |
154 | 172.16.18.91 | |
155 | [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/volumes | |
156 | USE STT VLID[0] VLID[1] VLID[2] NAME | |
157 | 1 Val 20000000 20000001 20000002 root.afs | |
1da177e4 | 158 | |
0795e7c0 DH |
159 | |
160 | ================= | |
1da177e4 LT |
161 | THE CELL DATABASE |
162 | ================= | |
163 | ||
0795e7c0 DH |
164 | The filesystem maintains an internal database of all the cells it knows and the |
165 | IP addresses of the volume location servers for those cells. The cell to which | |
166 | the system belongs is added to the database when insmod is performed by the | |
167 | "rootcell=" argument or, if compiled in, using a "kafs.rootcell=" argument on | |
168 | the kernel command line. | |
1da177e4 LT |
169 | |
170 | Further cells can be added by commands similar to the following: | |
171 | ||
172 | echo add CELLNAME VLADDR[:VLADDR][:VLADDR]... >/proc/fs/afs/cells | |
173 | echo add grand.central.org 18.7.14.88:128.2.191.224 >/proc/fs/afs/cells | |
174 | ||
175 | No other cell database operations are available at this time. | |
176 | ||
177 | ||
0795e7c0 DH |
178 | ======== |
179 | SECURITY | |
180 | ======== | |
181 | ||
182 | Secure operations are initiated by acquiring a key using the klog program. A | |
183 | very primitive klog program is available at: | |
184 | ||
185 | http://people.redhat.com/~dhowells/rxrpc/klog.c | |
186 | ||
187 | This should be compiled by: | |
188 | ||
189 | make klog LDLIBS="-lcrypto -lcrypt -lkrb4 -lkeyutils" | |
190 | ||
191 | And then run as: | |
192 | ||
193 | ./klog | |
194 | ||
195 | Assuming it's successful, this adds a key of type RxRPC, named for the service | |
196 | and cell, eg: "afs@<cellname>". This can be viewed with the keyctl program or | |
197 | by cat'ing /proc/keys: | |
198 | ||
199 | [root@andromeda ~]# keyctl show | |
200 | Session Keyring | |
201 | -3 --alswrv 0 0 keyring: _ses.3268 | |
202 | 2 --alswrv 0 0 \_ keyring: _uid.0 | |
203 | 111416553 --als--v 0 0 \_ rxrpc: afs@CAMBRIDGE.REDHAT.COM | |
204 | ||
205 | Currently the username, realm, password and proposed ticket lifetime are | |
206 | compiled in to the program. | |
207 | ||
208 | It is not required to acquire a key before using AFS facilities, but if one is | |
209 | not acquired then all operations will be governed by the anonymous user parts | |
210 | of the ACLs. | |
211 | ||
212 | If a key is acquired, then all AFS operations, including mounts and automounts, | |
213 | made by a possessor of that key will be secured with that key. | |
214 | ||
215 | If a file is opened with a particular key and then the file descriptor is | |
216 | passed to a process that doesn't have that key (perhaps over an AF_UNIX | |
217 | socket), then the operations on the file will be made with key that was used to | |
218 | open the file. | |
219 | ||
220 | ||
221 | ======== | |
1da177e4 LT |
222 | EXAMPLES |
223 | ======== | |
224 | ||
0795e7c0 DH |
225 | Here's what I use to test this. Some of the names and IP addresses are local |
226 | to my internal DNS. My "root.afs" partition has a mount point within it for | |
1da177e4 LT |
227 | some public volumes volumes. |
228 | ||
0795e7c0 DH |
229 | insmod /tmp/rxrpc.o |
230 | insmod /tmp/rxkad.o | |
231 | insmod /tmp/kafs.o rootcell=cambridge.redhat.com:172.16.18.91 | |
1da177e4 LT |
232 | |
233 | mount -t afs \%root.afs. /afs | |
234 | mount -t afs \%cambridge.redhat.com:root.cell. /afs/cambridge.redhat.com/ | |
235 | ||
0795e7c0 | 236 | echo add grand.central.org 18.7.14.88:128.2.191.224 > /proc/fs/afs/cells |
1da177e4 LT |
237 | mount -t afs "#grand.central.org:root.cell." /afs/grand.central.org/ |
238 | mount -t afs "#grand.central.org:root.archive." /afs/grand.central.org/archive | |
239 | mount -t afs "#grand.central.org:root.contrib." /afs/grand.central.org/contrib | |
240 | mount -t afs "#grand.central.org:root.doc." /afs/grand.central.org/doc | |
241 | mount -t afs "#grand.central.org:root.project." /afs/grand.central.org/project | |
242 | mount -t afs "#grand.central.org:root.service." /afs/grand.central.org/service | |
243 | mount -t afs "#grand.central.org:root.software." /afs/grand.central.org/software | |
244 | mount -t afs "#grand.central.org:root.user." /afs/grand.central.org/user | |
245 | ||
1da177e4 LT |
246 | umount /afs |
247 | rmmod kafs | |
0795e7c0 | 248 | rmmod rxkad |
1da177e4 | 249 | rmmod rxrpc |