]>
Commit | Line | Data |
---|---|---|
0795e7c0 | 1 | ==================== |
1da177e4 LT |
2 | kAFS: AFS FILESYSTEM |
3 | ==================== | |
4 | ||
0795e7c0 DH |
5 | Contents: |
6 | ||
7 | - Overview. | |
8 | - Usage. | |
9 | - Mountpoints. | |
4d673da1 | 10 | - Dynamic root. |
0795e7c0 DH |
11 | - Proc filesystem. |
12 | - The cell database. | |
13 | - Security. | |
6f8880d8 | 14 | - The @sys substitution. |
0795e7c0 DH |
15 | |
16 | ||
17 | ======== | |
18 | OVERVIEW | |
19 | ======== | |
1da177e4 | 20 | |
0795e7c0 DH |
21 | This filesystem provides a fairly simple secure AFS filesystem driver. It is |
22 | under development and does not yet provide the full feature set. The features | |
23 | it does support include: | |
1da177e4 | 24 | |
0795e7c0 | 25 | (*) Security (currently only AFS kaserver and KerberosIV tickets). |
1da177e4 | 26 | |
0dc9aa84 | 27 | (*) File reading and writing. |
1da177e4 | 28 | |
0795e7c0 DH |
29 | (*) Automounting. |
30 | ||
0dc9aa84 | 31 | (*) Local caching (via fscache). |
0795e7c0 | 32 | |
0dc9aa84 | 33 | It does not yet support the following AFS features: |
0795e7c0 DH |
34 | |
35 | (*) pioctl() system call. | |
36 | ||
37 | ||
38 | =========== | |
39 | COMPILATION | |
40 | =========== | |
41 | ||
42 | The filesystem should be enabled by turning on the kernel configuration | |
43 | options: | |
44 | ||
45 | CONFIG_AF_RXRPC - The RxRPC protocol transport | |
46 | CONFIG_RXKAD - The RxRPC Kerberos security handler | |
47 | CONFIG_AFS - The AFS filesystem | |
48 | ||
49 | Additionally, the following can be turned on to aid debugging: | |
50 | ||
51 | CONFIG_AF_RXRPC_DEBUG - Permit AF_RXRPC debugging to be enabled | |
52 | CONFIG_AFS_DEBUG - Permit AFS debugging to be enabled | |
53 | ||
54 | They permit the debugging messages to be turned on dynamically by manipulating | |
55 | the masks in the following files: | |
56 | ||
57 | /sys/module/af_rxrpc/parameters/debug | |
0dc9aa84 | 58 | /sys/module/kafs/parameters/debug |
0795e7c0 DH |
59 | |
60 | ||
61 | ===== | |
1da177e4 LT |
62 | USAGE |
63 | ===== | |
64 | ||
65 | When inserting the driver modules the root cell must be specified along with a | |
66 | list of volume location server IP addresses: | |
67 | ||
88c4845d | 68 | modprobe rxrpc |
0dc9aa84 | 69 | modprobe kafs rootcell=cambridge.redhat.com:172.16.18.73:172.16.18.91 |
1da177e4 | 70 | |
0795e7c0 DH |
71 | The first module is the AF_RXRPC network protocol driver. This provides the |
72 | RxRPC remote operation protocol and may also be accessed from userspace. See: | |
73 | ||
74 | Documentation/networking/rxrpc.txt | |
75 | ||
76 | The second module is the kerberos RxRPC security driver, and the third module | |
77 | is the actual filesystem driver for the AFS filesystem. | |
1da177e4 LT |
78 | |
79 | Once the module has been loaded, more modules can be added by the following | |
80 | procedure: | |
81 | ||
0dc9aa84 | 82 | echo add grand.central.org 18.9.48.14:128.2.203.61:130.237.48.87 >/proc/fs/afs/cells |
1da177e4 LT |
83 | |
84 | Where the parameters to the "add" command are the name of a cell and a list of | |
0795e7c0 | 85 | volume location servers within that cell, with the latter separated by colons. |
1da177e4 LT |
86 | |
87 | Filesystems can be mounted anywhere by commands similar to the following: | |
88 | ||
89 | mount -t afs "%cambridge.redhat.com:root.afs." /afs | |
90 | mount -t afs "#cambridge.redhat.com:root.cell." /afs/cambridge | |
91 | mount -t afs "#root.afs." /afs | |
92 | mount -t afs "#root.cell." /afs/cambridge | |
93 | ||
1da177e4 | 94 | Where the initial character is either a hash or a percent symbol depending on |
becfcc7e DH |
95 | whether you definitely want a R/W volume (percent) or whether you'd prefer a |
96 | R/O volume, but are willing to use a R/W volume instead (hash). | |
1da177e4 LT |
97 | |
98 | The name of the volume can be suffixes with ".backup" or ".readonly" to | |
99 | specify connection to only volumes of those types. | |
100 | ||
101 | The name of the cell is optional, and if not given during a mount, then the | |
0dc9aa84 | 102 | named volume will be looked up in the cell specified during modprobe. |
1da177e4 LT |
103 | |
104 | Additional cells can be added through /proc (see later section). | |
105 | ||
106 | ||
0795e7c0 | 107 | =========== |
1da177e4 LT |
108 | MOUNTPOINTS |
109 | =========== | |
110 | ||
0795e7c0 DH |
111 | AFS has a concept of mountpoints. In AFS terms, these are specially formatted |
112 | symbolic links (of the same form as the "device name" passed to mount). kAFS | |
113 | presents these to the user as directories that have a follow-link capability | |
114 | (ie: symbolic link semantics). If anyone attempts to access them, they will | |
115 | automatically cause the target volume to be mounted (if possible) on that site. | |
1da177e4 | 116 | |
0795e7c0 DH |
117 | Automatically mounted filesystems will be automatically unmounted approximately |
118 | twenty minutes after they were last used. Alternatively they can be unmounted | |
119 | directly with the umount() system call. | |
1da177e4 | 120 | |
0795e7c0 DH |
121 | Manually unmounting an AFS volume will cause any idle submounts upon it to be |
122 | culled first. If all are culled, then the requested volume will also be | |
123 | unmounted, otherwise error EBUSY will be returned. | |
1da177e4 | 124 | |
0795e7c0 DH |
125 | This can be used by the administrator to attempt to unmount the whole AFS tree |
126 | mounted on /afs in one go by doing: | |
1da177e4 | 127 | |
0795e7c0 | 128 | umount /afs |
1da177e4 LT |
129 | |
130 | ||
4d673da1 DH |
131 | ============ |
132 | DYNAMIC ROOT | |
133 | ============ | |
134 | ||
135 | A mount option is available to create a serverless mount that is only usable | |
136 | for dynamic lookup. Creating such a mount can be done by, for example: | |
137 | ||
138 | mount -t afs none /afs -o dyn | |
139 | ||
140 | This creates a mount that just has an empty directory at the root. Attempting | |
141 | to look up a name in this directory will cause a mountpoint to be created that | |
142 | looks up a cell of the same name, for example: | |
143 | ||
144 | ls /afs/grand.central.org/ | |
145 | ||
146 | ||
0795e7c0 | 147 | =============== |
1da177e4 LT |
148 | PROC FILESYSTEM |
149 | =============== | |
150 | ||
1da177e4 LT |
151 | The AFS modules creates a "/proc/fs/afs/" directory and populates it: |
152 | ||
0795e7c0 DH |
153 | (*) A "cells" file that lists cells currently known to the afs module and |
154 | their usage counts: | |
155 | ||
156 | [root@andromeda ~]# cat /proc/fs/afs/cells | |
157 | USE NAME | |
158 | 3 cambridge.redhat.com | |
1da177e4 LT |
159 | |
160 | (*) A directory per cell that contains files that list volume location | |
161 | servers, volumes, and active servers known within that cell. | |
162 | ||
0795e7c0 DH |
163 | [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/servers |
164 | USE ADDR STATE | |
165 | 4 172.16.18.91 0 | |
166 | [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/vlservers | |
167 | ADDRESS | |
168 | 172.16.18.91 | |
169 | [root@andromeda ~]# cat /proc/fs/afs/cambridge.redhat.com/volumes | |
170 | USE STT VLID[0] VLID[1] VLID[2] NAME | |
171 | 1 Val 20000000 20000001 20000002 root.afs | |
1da177e4 | 172 | |
0795e7c0 DH |
173 | |
174 | ================= | |
1da177e4 LT |
175 | THE CELL DATABASE |
176 | ================= | |
177 | ||
0795e7c0 DH |
178 | The filesystem maintains an internal database of all the cells it knows and the |
179 | IP addresses of the volume location servers for those cells. The cell to which | |
0dc9aa84 | 180 | the system belongs is added to the database when modprobe is performed by the |
0795e7c0 DH |
181 | "rootcell=" argument or, if compiled in, using a "kafs.rootcell=" argument on |
182 | the kernel command line. | |
1da177e4 LT |
183 | |
184 | Further cells can be added by commands similar to the following: | |
185 | ||
186 | echo add CELLNAME VLADDR[:VLADDR][:VLADDR]... >/proc/fs/afs/cells | |
0dc9aa84 | 187 | echo add grand.central.org 18.9.48.14:128.2.203.61:130.237.48.87 >/proc/fs/afs/cells |
1da177e4 LT |
188 | |
189 | No other cell database operations are available at this time. | |
190 | ||
191 | ||
0795e7c0 DH |
192 | ======== |
193 | SECURITY | |
194 | ======== | |
195 | ||
196 | Secure operations are initiated by acquiring a key using the klog program. A | |
197 | very primitive klog program is available at: | |
198 | ||
199 | http://people.redhat.com/~dhowells/rxrpc/klog.c | |
200 | ||
201 | This should be compiled by: | |
202 | ||
203 | make klog LDLIBS="-lcrypto -lcrypt -lkrb4 -lkeyutils" | |
204 | ||
205 | And then run as: | |
206 | ||
207 | ./klog | |
208 | ||
209 | Assuming it's successful, this adds a key of type RxRPC, named for the service | |
210 | and cell, eg: "afs@<cellname>". This can be viewed with the keyctl program or | |
211 | by cat'ing /proc/keys: | |
212 | ||
213 | [root@andromeda ~]# keyctl show | |
214 | Session Keyring | |
215 | -3 --alswrv 0 0 keyring: _ses.3268 | |
216 | 2 --alswrv 0 0 \_ keyring: _uid.0 | |
217 | 111416553 --als--v 0 0 \_ rxrpc: afs@CAMBRIDGE.REDHAT.COM | |
218 | ||
219 | Currently the username, realm, password and proposed ticket lifetime are | |
220 | compiled in to the program. | |
221 | ||
222 | It is not required to acquire a key before using AFS facilities, but if one is | |
223 | not acquired then all operations will be governed by the anonymous user parts | |
224 | of the ACLs. | |
225 | ||
226 | If a key is acquired, then all AFS operations, including mounts and automounts, | |
227 | made by a possessor of that key will be secured with that key. | |
228 | ||
229 | If a file is opened with a particular key and then the file descriptor is | |
230 | passed to a process that doesn't have that key (perhaps over an AF_UNIX | |
231 | socket), then the operations on the file will be made with key that was used to | |
232 | open the file. | |
6f8880d8 DH |
233 | |
234 | ||
235 | ===================== | |
236 | THE @SYS SUBSTITUTION | |
237 | ===================== | |
238 | ||
239 | The list of up to 16 @sys substitutions for the current network namespace can | |
240 | be configured by writing a list to /proc/fs/afs/sysname: | |
241 | ||
242 | [root@andromeda ~]# echo foo amd64_linux_26 >/proc/fs/afs/sysname | |
243 | ||
244 | or cleared entirely by writing an empty list: | |
245 | ||
246 | [root@andromeda ~]# echo >/proc/fs/afs/sysname | |
247 | ||
248 | The current list for current network namespace can be retrieved by: | |
249 | ||
250 | [root@andromeda ~]# cat /proc/fs/afs/sysname | |
251 | foo | |
252 | amd64_linux_26 | |
253 | ||
254 | When @sys is being substituted for, each element of the list is tried in the | |
255 | order given. | |
256 | ||
257 | By default, the list will contain one item that conforms to the pattern | |
258 | "<arch>_linux_26", amd64 being the name for x86_64. |