Avoid busy loop on rsync exit status 12 or 13.
[dss.git] / dss.ggo
1 # Copyright (C) 2008-2009 Andre Noll <maan@systemlinux.org>
2 #
3 # Licensed under the GPL v2. For licencing details see COPYING.
4
5 package "dss"
6 version "0.1.3"
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 mostly useful for the run command if --daemon
82 is also given.
83 "
84
85 ##################
86 section "Commands"
87 ##################
88
89 defgroup "command"
90 #=================
91 groupdesc="
92 dss supports a couple of commands each of which corresponds
93 to a different command line option. Exactly one of these
94 options must be given.
95
96 "
97 required
98
99 groupoption "create" C
100 #~~~~~~~~~~~~~~~~~~~~~
101 "Create a new snapshot"
102 group="command"
103 details="
104 Execute the rsync command to create a new snapshot. Note that
105 this command does not care about free disk space.
106 "
107
108 groupoption "prune" P
109 #~~~~~~~~~~~~~~~~~~~~
110 "Remove redundant and outdated snapshots"
111 group="command"
112 details="
113 A snapshot is considered outdated if its interval number
114 is greater or equal than the specified number of unit
115 intervals. See the \"Intervals\" section below for the precise
116 definition of these terms.
117
118 A snapshot is said to be redundant if it belongs to an
119 interval that already contains more than the desired number
120 of snapshots.
121
122 The prune command gets rid of both outdated and redundant
123 snapshots.
124 "
125
126 groupoption "ls" L
127 #~~~~~~~~~~~~~~~~~
128 "Print a list of all snapshots"
129 group="command"
130 details="
131 The list will contain all snapshots no matter of their state,
132 i. e. incomplete snapshots and snapshots being deleted will
133 also be listed.
134 "
135
136 groupoption "run" R
137 #~~~~~~~~~~~~~~~~~~
138 "Start creating and pruning snapshots"
139 group="command"
140 details="
141 This is the main mode of operation. Snapshots will be created
142 in an endless loop as needed and pruned automatically. The loop
143 only terminates on fatal errors or if a terminating signal was
144 received. See also the --exit-hook option.
145 "
146
147 ###############################
148 section "Rsync-related options"
149 ###############################
150
151 option "remote-host" H
152 #~~~~~~~~~~~~~~~~~~~~~
153 "Remote host"
154 string typestr="hostname"
155 default="localhost"
156 optional
157 details="
158 If this option is given and its value differs from the local
159 host, then rsync uses ssh. Make sure there is no password
160 needed for the ssh connection. To achieve that, use public key
161 authentication for ssh and, if needed, set the remote user name
162 by using the --remote-user option.
163 "
164
165 option "remote-user" U
166 #~~~~~~~~~~~~~~~~~~~~~
167 "Remote user name (default: current user)"
168 string typestr="username"
169 optional
170 details="
171 Set this if the user running dss is different from the
172 user at the remote host when using ssh.
173 "
174
175 option "source-dir" -
176 #~~~~~~~~~~~~~~~~~~~~
177 "The data directory"
178 string typestr="dirname"
179 required
180 details="
181 The directory on the remote host from which snapshots are
182 taken. Of course, the user specified as --remote-user must
183 have read access to this directory.
184 "
185
186 option "dest-dir" -
187 #~~~~~~~~~~~~~~~~~~
188 "Snapshot dir"
189 string typestr="dirname"
190 required
191 details="
192 The destination directory on the local host where snapshots
193 will be written. This must be writable by the user who runs
194 dss.
195 "
196
197 option "no-resume" -
198 #~~~~~~~~~~~~~~~~~~~
199 "Do not try to resume from previous runs"
200 flag off
201 details = "
202 Starting from version 0.1.4, dss tries to resume from a
203 previously cancelled dss instance by default. It does so by
204 looking at the status of the most recently created snapshot. If
205 this snapshot status is incomplete, its directory is reused
206 as the destination directory for a subsequent rsync run.
207
208 The --no-resume option deactivates this feature so that a new
209 directory is always used as the rsync destination directory.
210 "
211
212 option "rsync-option" O
213 #~~~~~~~~~~~~~~~~~~~~~~
214 "Further rsync options"
215 string typestr="option"
216 optional
217 multiple
218 details="
219 This option may be given multiple times. The given argument is
220 passed verbatim to the rsync command. Note that in order to use
221 rsync options that require an argument, you have to specify the
222 option and its argument as separate --rsync-options, like this:
223
224 --rsync-option --exclude --rsync-option /proc
225 "
226
227 ###################
228 section "Intervals"
229 ###################
230
231 option "unit-interval" u
232 #~~~~~~~~~~~~~~~~~~~~~~~
233 "The duration of a unit interval"
234 int typestr="days"
235 default="4"
236 optional
237 details="
238 dss snapshot aging is implemented in terms of intervals. There
239 are two command line options related to intervals: the
240 duration u of a \"unit\" interval and the number n of those
241 unit intervals.
242
243 dss removes any snapshots older than n times u and tries to
244 keep 2^(n - k - 1) snapshots in interval k, where the interval
245 number k counts from zero, zero being the most recent unit
246 interval.
247
248 In other words, the oldest snapshot will at most be u * n days
249 (= 20 days if default values are used) old. Moreover, there
250 are at most 2^n - 1 snapshots in total (i. e. 31 by default).
251 Observe that you have to create at least 2^(n - 1) snapshots
252 each interval for this to work out because that is the number
253 of snapshots in interval zero.
254 "
255
256 option "num-intervals" n
257 #~~~~~~~~~~~~~~~~~~~~~~~
258 "The number of unit intervals"
259 int typestr="num"
260 default="5"
261 optional
262
263 ###############
264 section "Hooks"
265 ###############
266
267 option "pre-create-hook" r
268 #~~~~~~~~~~~~~~~~~~~~~~~~~~
269 "Executed before snapshot creation"
270 string typestr="command"
271 optional
272 details="
273 Execute this command before trying to create a new snapshot.
274 If this command returns with a non-zero exit status, no
275 snapshot is being created and the operation is retried later.
276
277 For example, one might want to execute a script that checks
278 whether all snapshot-related file systems are properly mounted.
279
280 Another possible application of this is to return non-zero
281 during office hours in order to not slow down the file systems
282 by taking snapshots.
283 "
284
285 option "post-create-hook" o
286 #~~~~~~~~~~~~~~~~~~~~~~~~~~
287 "Executed after snapshot creation"
288 string typestr="command"
289 optional
290 details="
291 Execute this after a snapshot has successfully been
292 created. The full path of the newly created snapshot is
293 passed to the hook as the first argument. The exit code of
294 this hook is ignored.
295
296 For instance this hook can be used to count the number of
297 files per user and/or the disk usage patterns in order to
298 store them in a database for further analysis.
299 "
300
301 option "pre-remove-hook" -
302 #~~~~~~~~~~~~~~~~~~~~~~~~~~
303 "Executed before snapshot removal"
304 string typestr="command"
305 optional
306 details="
307 Execute this command before removing a snapshot. The full
308 path to the snapshot about to be deleted is passed to the
309 command as the first argument. If the command returns with
310 a non-zero exit status, no snapshot is being removed and the
311 operation is retried later.
312
313 For example, one might want to execute a script that checks
314 whether the snapshot to be deleted is currently used by
315 another process, e.g. by a tape-based backup system that runs
316 concurrently to dss.
317
318 Another possible application of this is to record disk-usage
319 patterns before and after snapshot removal.
320 "
321
322 option "post-remove-hook" -
323 #~~~~~~~~~~~~~~~~~~~~~~~~~~
324 "Executed after snapshot removal"
325 string typestr="command"
326 optional
327 details="
328 Execute this after a snapshot has successfully been removed. As
329 for the pre-remove hook, the full path of the removed snapshot
330 is passed to the hook as the first argument. The exit code
331 of this hook is ignored.
332 "
333
334 option "exit-hook" e
335 #~~~~~~~~~~~~~~~~~~~
336 "Executed if run command exits"
337 string typestr="command"
338 optional
339 details="
340 This hook is only used if the --run command was given which
341 instructs dss to run in an endless loop. The exit-hook gets
342 executed whenever this endless loop terminates. The reason
343 for terminating the loop is passed as the first argument.
344
345 One possible application for this hook is to send email to the
346 system administrator to let her know that no more snapshots
347 are going to be created.
348 "
349
350 ###############################
351 section "Disk space monitoring"
352 ###############################
353
354 option "min-free-mb" m
355 #~~~~~~~~~~~~~~~~~~~~~
356 "Minimal amount of free disk space"
357 int typestr="megabytes"
358 default="100"
359 optional
360 details="
361 If disk space on the file system containing the destination
362 directory gets low, \"dss --run\" will suspend the currently
363 running rsync process and will start to remove snapshots in
364 order to free disk space. This option specifies the minimal
365 amount of free disk space. If less than the given number of
366 megabytes is available, snapshots are being deleted. See also
367 the --min_free_percent and the min-free-percent-inodes options.
368
369 A value of zero deactivates this check.
370 "
371
372 option "min-free-percent" p
373 #~~~~~~~~~~~~~~~~~~~~~~~~~~
374 "Minimal percent of free disk space"
375 int typestr="percent"
376 default="2"
377 optional
378 details="
379 See --min-free-mb. Note that it is not recommended to set both
380 --min-free-mb and --min-free-percent to zero as this will
381 cause your file system to fill up quickly.
382 "
383 option "min-free-percent-inodes" i
384 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
385 "Minimal percent of free inodes"
386 int typestr="percent"
387 default="0"
388 optional
389 details="
390 Specify the minimum amount of free inodes on the file system
391 containing the destination dir. If less than that many inodes
392 are free, snapshot removal kicks in just as in case of low
393 disk space.
394
395 Note that not every file system supports the concept of inodes.
396 Moreover it is not possible to reliably detect whether this is
397 the case. Therefore this feature is disabled by default. It's
398 safe to enable it for ext3 file systems on linux though.
399
400 A value of zero (the default) deactivates this check.
401 "
402
403 option "keep-redundant" k
404 #~~~~~~~~~~~~~~~~~~~~~~~~
405 "Prune by disk space only"
406 flag off
407 details="
408 If this flag is not given dss removes redundant and outdated
409 snapshots automatically.
410
411 Otherwise, this feature is deactivated so that snapshots are
412 only being removed in case disk space or number of free inodes
413 becomes low. Use this flag if the file system containing the
414 destination directory is used for snapshots only.
415 "