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btrbk: add sanity check on timezone offset; add documentation about implications of long-iso time format

pull/88/head
Axel Burri 2016-04-23 14:37:24 +02:00
parent c7dd680537
commit efc260ef91
2 changed files with 22 additions and 10 deletions
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4
btrbk
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@ -3054,7 +3054,9 @@ sub timestamp($$;$)
} else { } else {
my $offset = timegm(@tm) - timelocal(@tm); my $offset = timegm(@tm) - timelocal(@tm);
if($offset < 0) { $ts .= '-'; $offset = -$offset; } else { $ts .= '+'; } if($offset < 0) { $ts .= '-'; $offset = -$offset; } else { $ts .= '+'; }
$ts .= sprintf('%02u%02u', int($offset / (60 * 60)), int($offset / 60) % 60); my $h = int($offset / (60 * 60));
die if($h > 24); # sanity check, something went really wrong
$ts .= sprintf('%02u%02u', $h, int($offset / 60) % 60);
} }
return $ts; return $ts;

28
doc/btrbk.conf.5
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@ -75,20 +75,22 @@ space-separated table format.
Timestamp format used as postfix for new snapshot subvolume Timestamp format used as postfix for new snapshot subvolume
names. Defaults to \[lq]short\[rq]. names. Defaults to \[lq]short\[rq].
.PP .PP
.IP \fBshort\fR .IP \fBshort\fR 10
YYYYMMDD[_N] (e.g. "20150825", "20150825_1") YYYYMMDD[_N] (e.g. "20150825", "20150825_1")
.IP \fBlong\fR .IP \fBlong\fR 10
YYYYMMDD<T>hhmm[_N] (e.g. "20150825T1531") YYYYMMDD<T>hhmm[_N] (e.g. "20150825T1531")
.IP \fBlong-iso\fR .IP \fBlong-iso\fR 10
YYYYMMDD<T>hhmmss\[t+-]hhmm[_N] (e.g. "20150825T153123+0200") YYYYMMDD<T>hhmmss\[t+-]hhmm[_N] (e.g. "20150825T153123+0200")
.PP .PP
Note that a postfix "_N" is only appended to the timestamp if a Note that a postfix "_N" is appended to the timestamp if a snapshot or
snapshot/backup already exists with the timestamp of current backup already exists with the timestamp of current date/time.
date/time.
.PP .PP
Use \[lq]long-iso\[rq] if you want to make sure that btrbk never Use \[lq]long-iso\[rq] if you want to make sure that btrbk never
creates ambiguous time stamps (which can happen if multiple snapshots creates ambiguous time stamps (which can happen if multiple snapshots
are created during a daylight saving time clock change). are created during a daylight saving time clock change).
.PP
Note that using \[lq]long-iso\[rq] has implications on the scheduling,
see RETENTION POLICY (caveats) below.
.RE .RE
.PP .PP
\fBsnapshot_dir\fR <directory> \fBsnapshot_dir\fR <directory>
@ -289,11 +291,19 @@ running btrbk.
.PP .PP
Caveats: Caveats:
.IP \[bu] 2 .IP \[bu] 2
If you run a setup with several btrbk instances (e.g. one
snapshot-only instance per remote client, and a separate fetch-only
instance on the backup server), it makes perfectly sense to run btrbk
with different local time on the clients, in order to make sure the
backups from all the remote hosts are preserved for "midnight", and
not at "00:00 UTC" (which would be "14:00" in Honolulu). If you want
this behaviour, do NOT use "timestamp_format long-iso".
.IP \[bu] 2
If "timestamp_format long-iso" is set, running btrbk from different If "timestamp_format long-iso" is set, running btrbk from different
time zones leads to different interpretation of "first in day, week, time zones leads to different interpretation of "first in day, week,
month, or year". So with this setup, make sure to run btrbk with the month, or year". Make sure to run btrbk with the same time zone on
same time zone on every host (e.g. by setting the TZ environment every host, e.g. by setting the TZ environment variable (see
variable). tzset(3)).
.SH TARGET TYPES .SH TARGET TYPES
.PP .PP
\fBsend-receive\fR \fBsend-receive\fR