+# Copyright (C) 2008-2010 Andre Noll <maan@tuebingen.mpg.de>
#
+# Licensed under the GPL v2. For licencing details see COPYING.
+
package "dss"
-version "0.0.4"
+version "0.1.6"
purpose "the dyadic snapshot scheduler
dss creates hardlink-based snapshots of a given directory on a remote
dependon="logfile"
details="
Note that dss refuses to start in daemon mode if no logfile
- was specified. This option is mostly useful in conjuction
+ was specified. This option is mostly useful in conjunction
with the -R option described below.
Note that it is not possible to change whether dss runs as
"Logfile for the dss daemon process"
string typestr="filename"
optional
-details="
- This option is mostly useful for the run command if --daemon
- is also given.
+details = "
+ This option is only honored if both --run and --daemon are
+ given. Otherwise it is silently ignored and log output is
+ written to stderr.
"
+##################
+section "Commands"
+##################
+
defgroup "command"
#=================
groupdesc="
dss supports a couple of commands each of which corresponds
to a different command line option. Exactly one of these
options must be given.
+
"
required
groupoption "prune" P
#~~~~~~~~~~~~~~~~~~~~
-"Remove a redundant snapshot"
+"Remove redundant and outdated snapshots"
group="command"
details="
- A snapshot is considered redundant if it ether belongs to
- an interval greater than the maximum number of intervals,
- or if it belongs to an interval that already contains more
- than the desired number of snapshots.
+ A snapshot is considered outdated if its interval number
+ is greater or equal than the specified number of unit
+ intervals. See the \"Intervals\" section below for the precise
+ definition of these terms.
+
+ A snapshot is said to be redundant if it belongs to an
+ interval that already contains more than the desired number
+ of snapshots.
+
+ The prune command gets rid of both outdated and redundant
+ snapshots.
"
groupoption "ls" L
group="command"
details="
This is the main mode of operation. Snapshots will be created
- as needed and pruned automatically.
+ in an endless loop as needed and pruned automatically. The loop
+ only terminates on fatal errors or if a terminating signal was
+ received. See also the --exit-hook option.
+"
+
+groupoption "kill" K
+#~~~~~~~~~~~~~~~~~~~
+"Kill a running dss process"
+group="command"
+details="
+ This sends SIGTERM to the dss process that corresponds to the
+ given config file. If --dry-run is given, the PID of the dss
+ process is written to stdout, but no signal is sent.
+"
+
+groupoption "reload" -
+#~~~~~~~~~~~~~~~~~~~~~
+"force a running dss process to reload its config file"
+group="command"
+details="
+ This differs from --kill only in that SIGHUP rather than SIGTERM
+ is sent to the dss process.
"
###############################
dss.
"
+option "no-resume" -
+#~~~~~~~~~~~~~~~~~~~
+"Do not try to resume from previous runs"
+flag off
+details = "
+ Starting from version 0.1.4, dss tries to resume from a
+ previously cancelled dss instance by default. It does so by
+ looking at the status of the most recently created snapshot. If
+ this snapshot status is incomplete, its directory is reused
+ as the destination directory for a subsequent rsync run.
+
+ The --no-resume option deactivates this feature so that a new
+ directory is always used as the rsync destination directory.
+"
+
option "rsync-option" O
#~~~~~~~~~~~~~~~~~~~~~~
"Further rsync options"
optional
multiple
details="
- These option may be given multiple times. The arguments passed
- to that option are passed verbatim to the rsync command.
+ This option may be given multiple times. The given argument is
+ passed verbatim to the rsync command. Note that in order to use
+ rsync options that require an argument, you have to specify the
+ option and its argument as separate --rsync-options, like this:
+
+ --rsync-option --exclude --rsync-option /proc
"
-option "exclude-patterns" e
-#~~~~~~~~~~~~~~~~~~~~~~~~~~
-"Rsync exclude patterns"
-string typestr="path"
+option "max-rsync-errors" -
+"Terminate after this many rsync failures"
+int typestr="count"
+default="10"
optional
+details="
+ Only relevant when operating in --run mode (see above). If
+ the rsync process exits with a fatal error, dss restarts
+ the command in the hope that the problem is transient
+ and subsequent rsync runs succeed. After the given number
+ of consecutive rsync error exits, however, dss gives up,
+ executes the exit hook and terminates. Set this to zero if
+ dss should exit immediately on the first rsync error.
+
+ The only non-fatal error is when rsync exits with code 24. This
+ indicates a partial transfer due to vanished source files
+ and happens frequently when snapshotting a directory which
+ is concurrently being modified.
+"
###################
section "Intervals"
unit intervals.
dss removes any snapshots older than n times u and tries to
- keep 2^(k-1) snapshots in interval k, where the interval number
- k counts from zero, zero being the most recent unit interval.
+ keep 2^(n - k - 1) snapshots in interval k, where the interval
+ number k counts from zero, zero being the most recent unit
+ interval.
In other words, the oldest snapshot will at most be u * n days
(= 20 days if default values are used) old. Moreover, there
are at most 2^n - 1 snapshots in total (i. e. 31 by default).
- Observe that you have to create at least 2 ^ (n - 1) snapshots
+ Observe that you have to create at least 2^(n - 1) snapshots
each interval for this to work out because that is the number
of snapshots in interval zero.
"
#~~~~~~~~~~~~~~~~~~~~~~~~~~
"Executed before snapshot creation"
string typestr="command"
+default = "true"
optional
details="
Execute this command before trying to create a new snapshot.
#~~~~~~~~~~~~~~~~~~~~~~~~~~
"Executed after snapshot creation"
string typestr="command"
+default = "true"
optional
details="
Execute this after a snapshot has successfully been
- created. The full path of the newly created snapshot is passed
- to the hook as the first argument. The return value of that
- hook is ignored.
+ created. The full path of the newly created snapshot is
+ passed to the hook as the first argument. The exit code of
+ this hook is ignored.
For instance this hook can be used to count the number of
files per user and/or the disk usage patterns in order to
- store them in a database for further treatment.
+ store them in a database for further analysis.
+"
+
+option "pre-remove-hook" -
+#~~~~~~~~~~~~~~~~~~~~~~~~~~
+"Executed before snapshot removal"
+string typestr="command"
+default = "true"
+optional
+details="
+ Execute this command before removing a snapshot. The full
+ path to the snapshot about to be deleted is passed to the
+ command as the first argument. If the command returns with
+ a non-zero exit status, no snapshot is being removed and the
+ operation is retried later.
+
+ For example, one might want to execute a script that checks
+ whether the snapshot to be deleted is currently used by
+ another process, e.g. by a tape-based backup system that runs
+ concurrently to dss.
+
+ Another possible application of this is to record disk-usage
+ patterns before and after snapshot removal.
+"
+
+option "post-remove-hook" -
+#~~~~~~~~~~~~~~~~~~~~~~~~~~
+"Executed after snapshot removal"
+string typestr="command"
+default = "true"
+optional
+details="
+ Execute this after a snapshot has successfully been removed. As
+ for the pre-remove hook, the full path of the removed snapshot
+ is passed to the hook as the first argument. The exit code
+ of this hook is ignored.
+"
+
+option "exit-hook" e
+#~~~~~~~~~~~~~~~~~~~
+"Executed if run command exits"
+string typestr="command"
+default = "true"
+optional
+details="
+ This hook is only used if the --run command was given which
+ instructs dss to run in an endless loop. The exit-hook gets
+ executed whenever this endless loop terminates. The reason
+ for terminating the loop is passed as the first argument.
+
+ One possible application for this hook is to send email to the
+ system administrator to let her know that no more snapshots
+ are going to be created.
"
###############################
details="
Specify the minimum amount of free inodes on the file system
containing the destination dir. If less than that many inodes
- are free, snatshot removal kicks in just as in case of low
+ are free, snapshot removal kicks in just as in case of low
disk space.
Note that not every file system supports the concept of inodes.
Moreover it is not possible to reliably detect whether this is
the case. Therefore this feature is disabled by default. It's
- safe to enable it for ext3 file systems on linux though.
+ safe to enable it for ext2/ext3/ext4 file systems on linux
+ though.
A value of zero (the default) deactivates this check.
"
+
+option "keep-redundant" k
+#~~~~~~~~~~~~~~~~~~~~~~~~
+"Prune by disk space only"
+flag off
+details="
+ If this flag is not given dss removes redundant and outdated
+ snapshots automatically.
+
+ Otherwise, this feature is deactivated so that snapshots are
+ only being removed in case disk space or number of free inodes
+ becomes low. Use this flag if the file system containing the
+ destination directory is used for snapshots only.
+"
+
+option "min-complete" -
+#~~~~~~~~~~~~~~~~~~~~~~
+"Minimal number of complete snapshots to keep"
+int typestr = "num"
+default = "1"
+optional
+details = "
+ This option is only relevant if snapshots must be deleted
+ because disk space gets low.
+
+ dss refuses to remove old snapshots if there are fewer complete
+ snapshots left than the given number. The default value of one
+ guarantees that at least one complete snapshot is available
+ at all times.
+
+ If only <num> complete snapshot are left, and there is not
+ enough disk space available for another snapshot, the program
+ terminates with a \"No space left on device\" error.
+"
projects / dss.git / blobdiff