Add more source code documentation.

[dss.git] / dss.ggo

diff --git a/dss.ggo b/dss.ggo
index a0a3503c6862c56eaeb15a75d7d55598eca3eac5..6e222d27727a8e201e825e234213426662a8cb64 100644 (file)
--- a/dss.ggo
+++ b/dss.ggo
@@ -21,6 +21,14 @@ details="
        configuration file. As usual, if an option is given both at
        the command line and in the configuration file, the command
        line option takes precedence.
        configuration file. As usual, if an option is given both at
        the command line and in the configuration file, the command
        line option takes precedence.

+
+       However, there is an important exception to this rule:
+       If the --run option was given (see below) then dss honors
+       SIGHUP and re-reads its configuration file whenever it
+       receives this signal. In this case the options in the config
+       file override any options that were previously given at the
+       command line. This allows to change the configuration of a
+       running dss process on the fly by sending SIGHUP.

 "
 
 option "daemon" d
 "
 
 option "daemon" d


@@ -30,8 +38,11 @@ flag off
 dependon="logfile"
 details="
        Note that dss refuses to start in daemon mode if no logfile
 dependon="logfile"
 details="
        Note that dss refuses to start in daemon mode if no logfile

-       was specified. This option makes sense only in conjunction
+       was specified. This option is mostly useful in conjuction

        with the -R option described below.
        with the -R option described below.

+
+       Note that it is not possible to change whether dss runs as
+       background daemon by sending SIGHUP.

 "
 
 option "dry-run" D
 "
 
 option "dry-run" D


@@ -55,7 +66,7 @@ int typestr="level"
 default="3"
 optional
 details="
 default="3"
 optional
 details="

-       Lower values mean less verbose logging.
+       Lower values mean more verbose logging.

 "
 
 option "logfile" -
 "
 
 option "logfile" -


@@ -71,8 +82,9 @@ details="
 defgroup "command"
 #=================
 groupdesc="
 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.
+       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
 
 "
 required
 


@@ -81,9 +93,10 @@ groupoption "create" C
 "Create a new snapshot"
 group="command"
 details="
 "Create a new snapshot"
 group="command"
 details="

-       Execute the rsync command to create a new snapshot. Note that this
-       command does not care about free disk space.
+       Execute the rsync command to create a new snapshot. Note that
+       this command does not care about free disk space.

 "
 "

+

 groupoption "prune" P
 #~~~~~~~~~~~~~~~~~~~~
 "Remove a redundant snapshot"
 groupoption "prune" P
 #~~~~~~~~~~~~~~~~~~~~
 "Remove a redundant snapshot"


@@ -146,7 +159,7 @@ option "source-dir" -
 #~~~~~~~~~~~~~~~~~~~~
 "The data directory"
 string typestr="dirname"
 #~~~~~~~~~~~~~~~~~~~~
 "The data directory"
 string typestr="dirname"

-optional
+required

 details="
        The directory on the remote host from which snapshots are
        taken.  Of course, the user specified as --remote-user must
 details="
        The directory on the remote host from which snapshots are
        taken.  Of course, the user specified as --remote-user must


@@ -157,7 +170,7 @@ option "dest-dir" -
 #~~~~~~~~~~~~~~~~~~
 "Snapshot dir"
 string typestr="dirname"
 #~~~~~~~~~~~~~~~~~~
 "Snapshot dir"
 string typestr="dirname"

-optional
+required

 details="
        The destination directory on the local host where snapshots
        will be written. This must be writable by the user who runs
 details="
        The destination directory on the local host where snapshots
        will be written. This must be writable by the user who runs


@@ -192,29 +205,21 @@ int typestr="days"
 default="4"
 optional
 details="
 default="4"
 optional
 details="

-       dss snapshot aging is implemented in terms of intervals. There are
-       two command line options related to intervals: the duration of a
-       \"unit\" interval and the number of those unit intervals.
-
-       dss removes any snapshots older than the given number of intervals
-       times the duration of a unit interval and tries to keep the following
-       number of snapshots per interval:
-
-               interval number         number of snapshots
-               ===============================================
-               0                       2 ^ (num-intervals - 1)
-               1                       2 ^ (num-intervals - 2)
-               2                       2 ^ (num-intervals - 3)
-               ...
-               num-intervals - 2                       2
-               num-intervals - 1                       1
-               num-intervals                           0
-
-       In other words, the oldest snapshot will at most be unit_interval *
-       num_intervals old (= 5 days * 4 = 20 days if default values are used).
-       Moreover, there are at most 2^num_intervals - 1 snapshots in total
-       (i. e. 31 by default).  Observe that you have to create at least
-       2 ^ (num_intervals - 1) snapshots each interval for this to work out.
+       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^(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.

 "
 
 option "num-intervals" n
 "
 
 option "num-intervals" n


@@ -232,29 +237,34 @@ option "pre-create-hook" r
 #~~~~~~~~~~~~~~~~~~~~~~~~~~
 "Executed before snapshot creation"
 string typestr="command"
 #~~~~~~~~~~~~~~~~~~~~~~~~~~
 "Executed before snapshot creation"
 string typestr="command"

-default="/bin/true"

 optional
 details="
        Execute this command before trying to create a new snapshot.
 optional
 details="
        Execute this command before trying to create a new snapshot.

-       If this command returns with a non-zero exit status, do not
-       perform the backup. One possible application of this is to
-       return non-zero during office hours in order to not slow down
-       the file systems by taking snapshots.
-"
+       If this command returns with a non-zero exit status, no
+       snapshot is being created and the operation is retried later.

 
 

+       For example, one might want to execute a script that checks
+       whether all snapshot-related file systems are properly mounted.
+
+       Another possible application of this is to return non-zero
+       during office hours in order to not slow down the file systems
+       by taking snapshots.
+"

 
 option "post-create-hook" o
 #~~~~~~~~~~~~~~~~~~~~~~~~~~
 "Executed after snapshot creation"
 string typestr="command"
 
 option "post-create-hook" o
 #~~~~~~~~~~~~~~~~~~~~~~~~~~
 "Executed after snapshot creation"
 string typestr="command"

-default="/bin/true"

 optional
 details="
 optional
 details="

-       Execute this after a snapshot has successfully been created
-       The return value on the command is ignored. For instance one
-       could count the number of files per user and/or the disk
-       usage patterns in order to store them in a database for
-       further treatment.
+       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.
+
+       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.

 "
 
 ###############################
 "
 
 ###############################