doc/man/lttng-snapshot.1.txt

   1 lttng-snapshot(1)
   2 =================
   3
   4
   5 NAME
   6 ----
   7 lttng-snapshot - Take LTTng snapshots and configure snapshot outputs
   8
   9
  10 SYNOPSIS
  11 --------
  12 Add a snapshot output:
  13
  14 [verse]
  15 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot add-output* [option:--max-size='SIZE']
  16       [option:--name='NAME'] [option:--session='SESSION']
  17       (option:--ctrl-url='URL' option:--data-url='URL' | 'URL')
  18
  19 Remove a snapshot output:
  20
  21 [verse]
  22 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot del-output* [option:--session='SESSION']
  23       ('ID' | 'NAME')
  24
  25 List current snapshot outputs:
  26
  27 [verse]
  28 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot list-output* [option:--session='SESSION']
  29
  30 Take a snapshot:
  31
  32 [verse]
  33 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot record* [option:--max-size='SIZE']
  34       [option:--name='NAME'] [option:--session='SESSION']
  35       (option:--ctrl-url='URL' option:--data-url='URL' | 'URL')
  36
  37
  38 DESCRIPTION
  39 -----------
  40 The `lttng snapshot` command manages the snapshot outputs and takes
  41 snapshots.
  42
  43 A _snapshot_ is a dump of the current sub-buffers of all the channels
  44 of a given tracing session. When a snapshot is taken, the memory dump
  45 is sent to the registered snapshot outputs.
  46
  47 The tracing session should be created in _snapshot mode_ to make sure
  48 that taking snapshots is allowed. This is done at tracing session
  49 creation time using the man:lttng-create(1) command's
  50 nloption:--snapshot option.
  51
  52 Note that, when a snapshot is taken, the sub-buffers are not cleared.
  53 This means that different recorded snapshots may contain the same
  54 events.
  55
  56 If you want, instead, to keep all the trace data, but divide it into
  57 archived chunks which are then free to process (just like snapshots),
  58 see the lttng-rotate(1) and lttng-enable-rotation(1) commands. Trace
  59 chunk archives do not overlap like snapshots can.
  60
  61
  62 Snapshot outputs
  63 ~~~~~~~~~~~~~~~~
  64 Snapshot outputs are the destinations of snapshot files when a
  65 snapshot is taken using the `record` action.
  66
  67 As of this version, only one snapshot output is allowed.
  68
  69 A snapshot output can be added using the `add-output` action. The
  70 output destination URL is set using either the 'URL' positional
  71 argument, or both the option:--ctrl-url and option:--data-url options.
  72 See man:lttng-create(1) to learn more about the URL format.
  73
  74 A name can be assigned to an output when adding it using the
  75 option:--name option. This name is part of the names of the
  76 snapshot files written to this output.
  77
  78 By default, the snapshot files can be as big as the sum of the
  79 sizes of all the sub-buffers or all the channels of the selected
  80 tracing session. The maximum total size of all the snapshot files can
  81 be configured using the option:--max-size option.
  82
  83 Snapshot outputs can be listed using the `list-output` action.
  84
  85 Snapshot outputs can be removed using the `del-output` action. The
  86 configured name can be used when removing an output, or an ID as
  87 listed by the `list-output` action.
  88
  89
  90 Taking a snapshot
  91 ~~~~~~~~~~~~~~~~~
  92 Taking a snapshot of the current tracing session is as easy as:
  93
  94 [role="term"]
  95 ----
  96 $ lttng snapshot record
  97 ----
  98
  99 This writes the snapshot files to the configured output. It is possible
 100 to use a custom, unregistered output at record time using the same
 101 options supported by the `add-output` action.
 102
 103 NOTE: Before taking a snapshot on a system with a high event throughput,
 104 it is recommended to first run `lttng stop` (see
 105 man:lttng-stop(1)). Otherwise, the snapshot could contain "holes",
 106 the result of the tracers overwriting unconsumed trace packets during
 107 the record operation. After the snapshot is recorded, the tracers can be
 108 started again with `lttng start` (see man:lttng-start(1)).
 109
 110
 111 include::common-cmd-options-head.txt[]
 112
 113
 114 Target
 115 ~~~~~~
 116 option:-s 'SESSION', option:--session='SESSION'::
 117     Take a snapshot of the sub-buffers of the channels contained in
 118     the tracing session named 'SESSION' instead of the current
 119     tracing session.
 120
 121
 122 Snapshot output
 123 ~~~~~~~~~~~~~~~
 124 option:-C 'URL', option:--ctrl-url='URL'::
 125     Set control path URL to 'URL' (must use option:--data-url option
 126     also).
 127
 128 option:-D 'URL', option:--data-url='URL'::
 129     Set data path URL to 'URL' (must use option:--ctrl-url option
 130     also).
 131
 132 option:-m 'SIZE', option:--max-size='SIZE'::
 133     Limit the total size of all the snapshot files written when
 134     recording a snapshot to 'SIZE' bytes. The `k` (kiB), `M` (MiB),
 135     and `G` (GiB) suffixes are supported.
 136
 137 option:-n 'NAME', option:--name='NAME'::
 138     Assign the name 'NAME' to the snapshot output.
 139
 140
 141 include::common-cmd-help-options.txt[]
 142
 143
 144 include::common-cmd-footer.txt[]
 145
 146
 147 SEE ALSO
 148 --------
 149 man:lttng(1)