NEWS update
[dss.git] / dss.ggo
1 # Copyright (C) 2008-2010 Andre Noll <maan@tuebingen.mpg.de>
2 #
3 # Licensed under the GPL v2. For licencing details see COPYING.
4
5 package "dss"
6 version "0.1.5"
7 purpose "the dyadic snapshot scheduler
8
9 dss creates hardlink-based snapshots of a given directory on a remote
10 or local host using rsync's link-dest feature.
11 "
12
13 #########################
14 section "General options"
15 #########################
16
17 option "config-file" c
18 #~~~~~~~~~~~~~~~~~~~~~
19 "(default='~/.dssrc')"
20 string typestr="filename"
21 optional
22 details="
23 Options may be given at the command line or in the
24 configuration file. As usual, if an option is given both at
25 the command line and in the configuration file, the command
26 line option takes precedence.
27
28 However, there is an important exception to this rule:
29 If the --run option was given (see below) then dss honors
30 SIGHUP and re-reads its configuration file whenever it
31 receives this signal. In this case the options in the config
32 file override any options that were previously given at the
33 command line. This allows to change the configuration of a
34 running dss process on the fly by sending SIGHUP.
35 "
36
37 option "daemon" d
38 #~~~~~~~~~~~~~~~~
39 "Run as background daemon"
40 flag off
41 dependon="logfile"
42 details="
43 Note that dss refuses to start in daemon mode if no logfile
44 was specified. This option is mostly useful in conjuction
45 with the -R option described below.
46
47 Note that it is not possible to change whether dss runs as
48 background daemon by sending SIGHUP.
49 "
50
51 option "dry-run" D
52 #~~~~~~~~~~~~~~~~~
53 "Only print what would be done"
54 flag off
55 details="
56 This flag does not make sense for all commands. The run
57 command refuses to start if this option was given. The ls
58 command silently ignores this flag.
59 "
60
61 #################
62 section "Logging"
63 #################
64
65 option "loglevel" l
66 #~~~~~~~~~~~~~~~~~~
67 "Set loglevel (0-6)"
68 int typestr="level"
69 default="3"
70 optional
71 details="
72 Lower values mean more verbose logging.
73 "
74
75 option "logfile" -
76 #~~~~~~~~~~~~~~~~~
77 "Logfile for the dss daemon process"
78 string typestr="filename"
79 optional
80 details = "
81 This option is only honored if both --run and --daemon are
82 given. Otherwise it is silently ignored and log output is
83 written to stderr.
84 "
85
86 ##################
87 section "Commands"
88 ##################
89
90 defgroup "command"
91 #=================
92 groupdesc="
93 dss supports a couple of commands each of which corresponds
94 to a different command line option. Exactly one of these
95 options must be given.
96
97 "
98 required
99
100 groupoption "create" C
101 #~~~~~~~~~~~~~~~~~~~~~
102 "Create a new snapshot"
103 group="command"
104 details="
105 Execute the rsync command to create a new snapshot. Note that
106 this command does not care about free disk space.
107 "
108
109 groupoption "prune" P
110 #~~~~~~~~~~~~~~~~~~~~
111 "Remove redundant and outdated snapshots"
112 group="command"
113 details="
114 A snapshot is considered outdated if its interval number
115 is greater or equal than the specified number of unit
116 intervals. See the \"Intervals\" section below for the precise
117 definition of these terms.
118
119 A snapshot is said to be redundant if it belongs to an
120 interval that already contains more than the desired number
121 of snapshots.
122
123 The prune command gets rid of both outdated and redundant
124 snapshots.
125 "
126
127 groupoption "ls" L
128 #~~~~~~~~~~~~~~~~~
129 "Print a list of all snapshots"
130 group="command"
131 details="
132 The list will contain all snapshots no matter of their state,
133 i. e. incomplete snapshots and snapshots being deleted will
134 also be listed.
135 "
136
137 groupoption "run" R
138 #~~~~~~~~~~~~~~~~~~
139 "Start creating and pruning snapshots"
140 group="command"
141 details="
142 This is the main mode of operation. Snapshots will be created
143 in an endless loop as needed and pruned automatically. The loop
144 only terminates on fatal errors or if a terminating signal was
145 received. See also the --exit-hook option.
146 "
147
148 groupoption "kill" K
149 #~~~~~~~~~~~~~~~~~~~
150 "Kill a running dss process"
151 group="command"
152 details="
153 This sends SIGTERM to the dss process that corresponds to the
154 given config file. If --dry-run is given, the PID of the dss
155 process is written to stdout, but no signal is sent.
156 "
157
158 groupoption "reload" -
159 #~~~~~~~~~~~~~~~~~~~~~
160 "force a running dss process to reload its config file"
161 group="command"
162 details="
163 This differs from --kill only in that SIGHUP rather than SIGTERM
164 is sent to the dss process.
165 "
166
167 ###############################
168 section "Rsync-related options"
169 ###############################
170
171 option "remote-host" H
172 #~~~~~~~~~~~~~~~~~~~~~
173 "Remote host"
174 string typestr="hostname"
175 default="localhost"
176 optional
177 details="
178 If this option is given and its value differs from the local
179 host, then rsync uses ssh. Make sure there is no password
180 needed for the ssh connection. To achieve that, use public key
181 authentication for ssh and, if needed, set the remote user name
182 by using the --remote-user option.
183 "
184
185 option "remote-user" U
186 #~~~~~~~~~~~~~~~~~~~~~
187 "Remote user name (default: current user)"
188 string typestr="username"
189 optional
190 details="
191 Set this if the user running dss is different from the
192 user at the remote host when using ssh.
193 "
194
195 option "source-dir" -
196 #~~~~~~~~~~~~~~~~~~~~
197 "The data directory"
198 string typestr="dirname"
199 required
200 details="
201 The directory on the remote host from which snapshots are
202 taken. Of course, the user specified as --remote-user must
203 have read access to this directory.
204 "
205
206 option "dest-dir" -
207 #~~~~~~~~~~~~~~~~~~
208 "Snapshot dir"
209 string typestr="dirname"
210 required
211 details="
212 The destination directory on the local host where snapshots
213 will be written. This must be writable by the user who runs
214 dss.
215 "
216
217 option "no-resume" -
218 #~~~~~~~~~~~~~~~~~~~
219 "Do not try to resume from previous runs"
220 flag off
221 details = "
222 Starting from version 0.1.4, dss tries to resume from a
223 previously cancelled dss instance by default. It does so by
224 looking at the status of the most recently created snapshot. If
225 this snapshot status is incomplete, its directory is reused
226 as the destination directory for a subsequent rsync run.
227
228 The --no-resume option deactivates this feature so that a new
229 directory is always used as the rsync destination directory.
230 "
231
232 option "rsync-option" O
233 #~~~~~~~~~~~~~~~~~~~~~~
234 "Further rsync options"
235 string typestr="option"
236 optional
237 multiple
238 details="
239 This option may be given multiple times. The given argument is
240 passed verbatim to the rsync command. Note that in order to use
241 rsync options that require an argument, you have to specify the
242 option and its argument as separate --rsync-options, like this:
243
244 --rsync-option --exclude --rsync-option /proc
245 "
246
247 ###################
248 section "Intervals"
249 ###################
250
251 option "unit-interval" u
252 #~~~~~~~~~~~~~~~~~~~~~~~
253 "The duration of a unit interval"
254 int typestr="days"
255 default="4"
256 optional
257 details="
258 dss snapshot aging is implemented in terms of intervals. There
259 are two command line options related to intervals: the
260 duration u of a \"unit\" interval and the number n of those
261 unit intervals.
262
263 dss removes any snapshots older than n times u and tries to
264 keep 2^(n - k - 1) snapshots in interval k, where the interval
265 number k counts from zero, zero being the most recent unit
266 interval.
267
268 In other words, the oldest snapshot will at most be u * n days
269 (= 20 days if default values are used) old. Moreover, there
270 are at most 2^n - 1 snapshots in total (i. e. 31 by default).
271 Observe that you have to create at least 2^(n - 1) snapshots
272 each interval for this to work out because that is the number
273 of snapshots in interval zero.
274 "
275
276 option "num-intervals" n
277 #~~~~~~~~~~~~~~~~~~~~~~~
278 "The number of unit intervals"
279 int typestr="num"
280 default="5"
281 optional
282
283 ###############
284 section "Hooks"
285 ###############
286
287 option "pre-create-hook" r
288 #~~~~~~~~~~~~~~~~~~~~~~~~~~
289 "Executed before snapshot creation"
290 string typestr="command"
291 default = "true"
292 optional
293 details="
294 Execute this command before trying to create a new snapshot.
295 If this command returns with a non-zero exit status, no
296 snapshot is being created and the operation is retried later.
297
298 For example, one might want to execute a script that checks
299 whether all snapshot-related file systems are properly mounted.
300
301 Another possible application of this is to return non-zero
302 during office hours in order to not slow down the file systems
303 by taking snapshots.
304 "
305
306 option "post-create-hook" o
307 #~~~~~~~~~~~~~~~~~~~~~~~~~~
308 "Executed after snapshot creation"
309 string typestr="command"
310 default = "true"
311 optional
312 details="
313 Execute this after a snapshot has successfully been
314 created. The full path of the newly created snapshot is
315 passed to the hook as the first argument. The exit code of
316 this hook is ignored.
317
318 For instance this hook can be used to count the number of
319 files per user and/or the disk usage patterns in order to
320 store them in a database for further analysis.
321 "
322
323 option "pre-remove-hook" -
324 #~~~~~~~~~~~~~~~~~~~~~~~~~~
325 "Executed before snapshot removal"
326 string typestr="command"
327 default = "true"
328 optional
329 details="
330 Execute this command before removing a snapshot. The full
331 path to the snapshot about to be deleted is passed to the
332 command as the first argument. If the command returns with
333 a non-zero exit status, no snapshot is being removed and the
334 operation is retried later.
335
336 For example, one might want to execute a script that checks
337 whether the snapshot to be deleted is currently used by
338 another process, e.g. by a tape-based backup system that runs
339 concurrently to dss.
340
341 Another possible application of this is to record disk-usage
342 patterns before and after snapshot removal.
343 "
344
345 option "post-remove-hook" -
346 #~~~~~~~~~~~~~~~~~~~~~~~~~~
347 "Executed after snapshot removal"
348 string typestr="command"
349 default = "true"
350 optional
351 details="
352 Execute this after a snapshot has successfully been removed. As
353 for the pre-remove hook, the full path of the removed snapshot
354 is passed to the hook as the first argument. The exit code
355 of this hook is ignored.
356 "
357
358 option "exit-hook" e
359 #~~~~~~~~~~~~~~~~~~~
360 "Executed if run command exits"
361 string typestr="command"
362 default = "true"
363 optional
364 details="
365 This hook is only used if the --run command was given which
366 instructs dss to run in an endless loop. The exit-hook gets
367 executed whenever this endless loop terminates. The reason
368 for terminating the loop is passed as the first argument.
369
370 One possible application for this hook is to send email to the
371 system administrator to let her know that no more snapshots
372 are going to be created.
373 "
374
375 ###############################
376 section "Disk space monitoring"
377 ###############################
378
379 option "min-free-mb" m
380 #~~~~~~~~~~~~~~~~~~~~~
381 "Minimal amount of free disk space"
382 int typestr="megabytes"
383 default="100"
384 optional
385 details="
386 If disk space on the file system containing the destination
387 directory gets low, \"dss --run\" will suspend the currently
388 running rsync process and will start to remove snapshots in
389 order to free disk space. This option specifies the minimal
390 amount of free disk space. If less than the given number of
391 megabytes is available, snapshots are being deleted. See also
392 the --min_free_percent and the min-free-percent-inodes options.
393
394 A value of zero deactivates this check.
395 "
396
397 option "min-free-percent" p
398 #~~~~~~~~~~~~~~~~~~~~~~~~~~
399 "Minimal percent of free disk space"
400 int typestr="percent"
401 default="2"
402 optional
403 details="
404 See --min-free-mb. Note that it is not recommended to set both
405 --min-free-mb and --min-free-percent to zero as this will
406 cause your file system to fill up quickly.
407 "
408 option "min-free-percent-inodes" i
409 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
410 "Minimal percent of free inodes"
411 int typestr="percent"
412 default="0"
413 optional
414 details="
415 Specify the minimum amount of free inodes on the file system
416 containing the destination dir. If less than that many inodes
417 are free, snapshot removal kicks in just as in case of low
418 disk space.
419
420 Note that not every file system supports the concept of inodes.
421 Moreover it is not possible to reliably detect whether this is
422 the case. Therefore this feature is disabled by default. It's
423 safe to enable it for ext2/ext3/ext4 file systems on linux
424 though.
425
426 A value of zero (the default) deactivates this check.
427 "
428
429 option "keep-redundant" k
430 #~~~~~~~~~~~~~~~~~~~~~~~~
431 "Prune by disk space only"
432 flag off
433 details="
434 If this flag is not given dss removes redundant and outdated
435 snapshots automatically.
436
437 Otherwise, this feature is deactivated so that snapshots are
438 only being removed in case disk space or number of free inodes
439 becomes low. Use this flag if the file system containing the
440 destination directory is used for snapshots only.
441 "
442
443 option "min-complete" -
444 #~~~~~~~~~~~~~~~~~~~~~~
445 "Minimal number of complete snapshots to keep"
446 int typestr = "num"
447 default = "1"
448 optional
449 details = "
450 This option is only relevant if snapshots must be deleted
451 because disk space gets low.
452
453 dss refuses to remove old snapshots if there are fewer complete
454 snapshots left than the given number. The default value of one
455 guarantees that at least one complete snapshot is available
456 at all times.
457
458 If only <num> complete snapshot are left, and there is not
459 enough disk space available for another snapshot, the program
460 terminates with a \"No space left on device\" error.
461 "