-# Copyright (C) 2008 Andre Noll <maan@systemlinux.org>
+# Copyright (C) 2008-2010 Andre Noll <maan@tuebingen.mpg.de>
#
# Licensed under the GPL v2. For licencing details see COPYING.
package "dss"
-version "0.1.2"
+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.
"
##################
"Remove redundant and outdated snapshots"
group="command"
details="
- A snapshot is considered outdated if it belongs to an interval
- greater than the maximum number of intervals. It is said to be
- redundant if it belongs to an interval that already contains
- more than the desired number of snapshots. This command gets
- rid of such 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+ A snapshot is considered outdated if its interval number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+ The prune command gets rid of both outdated and redundant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
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.
+"
+
###############################
section "Rsync-related options"
###############################
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"
--rsync-option --exclude --rsync-option /proc
"
+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"
###################
default="4"
optional
details="
- dss snapshot aging is implemented in terms of intervals. There
- are two command line options related to intervals: the
- duration u of a \"unit\" interval and the number n of those
- unit intervals.
-
- dss removes any snapshots older than n times u and tries to
- 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
- each interval for this to work out because that is the number
- of snapshots in interval zero.
+ Snapshot aging is implemented in terms of intervals. There are two
+ command line options related to intervals: the duration u of a unit
+ interval and the number of unit intervals, denoted n below.
+
+ dss removes snapshots older than n times u and tries to keep 2^(n -
+ k - 1) snapshots in interval k, where the interval number k counts
+ from zero to n - 1, with zero being the most recent unit interval.
+
+ Hence the oldest snapshot will at most be u * n days old (4 days *
+ 5 intervals = 20 days, if default values are used). Moreover, there
+ are at most 2^n - 1 snapshots in total (2^5 - 1 = 31 by default). Note
+ that for this to work out your system must be fast enough to create at
+ least 2^(n - 1) snapshots per unit interval (16 snapshots in 4 days =
+ one snapshot in 6 hours), because this is the number of snapshots in
+ interval zero.
"
option "num-intervals" n
int typestr="num"
default="5"
optional
+details="
+ Note that increasing this number by one doubles the total number of
+ snapshots. See the documentation of --unit-interval above.
+"
###############
section "Hooks"
#~~~~~~~~~~~~~~~~~~~~~~~~~~
"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
#~~~~~~~~~~~~~~~~~~~~~~~~~~
"Executed before snapshot removal"
string typestr="command"
+default = "true"
optional
details="
Execute this command before removing a snapshot. The full
#~~~~~~~~~~~~~~~~~~~~~~~~~~
"Executed after snapshot removal"
string typestr="command"
+default = "true"
optional
details="
Execute this after a snapshot has successfully been removed. As
#~~~~~~~~~~~~~~~~~~~
"Executed if run command exits"
string typestr="command"
+default = "true"
optional
details="
This hook is only used if the --run command was given which
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.
"
"Prune by disk space only"
flag off
details="
- If this flag is not given dss removes redundant and outdated
- snapshots automatically.
+ By default, redundant and outdated snapshots are removed automatically
+ to keep the number of snapshots in harmony with the configured
+ policy. If this flag is given, dss removes such snapshots only if
+ disk space or number of free inodes becomes low.
+"
- 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