Commit | Line | Data |
---|---|---|
12397c59 PP |
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] | |
ce19b9ed | 15 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot add-output* [option:--max-size='SIZE'] |
12397c59 PP |
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] | |
ce19b9ed | 22 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot del-output* [option:--session='SESSION'] |
12397c59 PP |
23 | ('ID' | 'NAME') |
24 | ||
25 | List current snapshot outputs: | |
26 | ||
27 | [verse] | |
ce19b9ed | 28 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot list-output* [option:--session='SESSION'] |
12397c59 PP |
29 | |
30 | Take a snapshot: | |
31 | ||
32 | [verse] | |
ce19b9ed | 33 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *snapshot record* [option:--max-size='SIZE'] |
12397c59 PP |
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 | taking snapshots is allowed. This is done at tracing session creation | |
7c1a4458 | 49 | time using the man:lttng-create(1) command. |
12397c59 PP |
50 | |
51 | Note that, when a snapshot is taken, the sub-buffers are not cleared. | |
52 | This means that different recorded snapshots may contain the same | |
53 | events. | |
54 | ||
55 | ||
56 | Snapshot outputs | |
57 | ~~~~~~~~~~~~~~~~ | |
58 | Snapshot outputs are the destinations of snapshot files when a | |
59 | snapshot is taken using the `record` action. | |
60 | ||
61 | As of this version, only one snapshot output is allowed. | |
62 | ||
63 | A snapshot output can be added using the `add-output` action. The | |
64 | output destination URL is set using either the 'URL' positional | |
65 | argument, or both the option:--ctrl-url and option:--data-url options. | |
7c1a4458 | 66 | See man:lttng-create(1) to learn more about the URL format. |
12397c59 PP |
67 | |
68 | A name can be assigned to an output when adding it using the | |
69 | option:--name option. This name is part of the names of the | |
70 | snapshot files written to this output. | |
71 | ||
72 | By default, the snapshot files can be as big as the sum of the | |
73 | sizes of all the sub-buffers or all the channels of the selected | |
74 | tracing session. The maximum total size of all the snapshot files can | |
75 | be configured using the option:--max-size option. | |
76 | ||
77 | Snapshot outputs can be listed using the `list-output` action. | |
78 | ||
79 | Snapshot outputs can be removed using the `del-output` action. The | |
80 | configured name can be used when removing an output, or an ID as | |
81 | listed by the `list-output` action. | |
82 | ||
83 | ||
84 | Taking a snapshot | |
85 | ~~~~~~~~~~~~~~~~~ | |
86 | Taking a snapshot of the current tracing session is as easy as: | |
87 | ||
88 | --------------------- | |
89 | lttng snapshot record | |
90 | --------------------- | |
91 | ||
92 | This writes the snapshot files to the configured output. It is possible | |
93 | to use a custom, unregistered output at record time using the same | |
94 | options supported by the `add-output` action. | |
95 | ||
96 | NOTE: Before taking a snapshot on a system with a high event throughput, | |
97 | it is recommended to first run `lttng stop` (see | |
7c1a4458 | 98 | man:lttng-stop(1)). Otherwise, the snapshot could contain "holes", |
12397c59 PP |
99 | the result of the tracers overwriting unconsumed trace packets during |
100 | the record operation. After the snapshot is recorded, the tracers can be | |
7c1a4458 | 101 | started again with `lttng start` (see man:lttng-start(1)). |
12397c59 PP |
102 | |
103 | ||
104 | include::common-cmd-options-head.txt[] | |
105 | ||
106 | ||
107 | Target | |
108 | ~~~~~~ | |
109 | option:-s, option:--session='SESSION':: | |
110 | Take a snapshot of the sub-buffers of the channels contained in | |
111 | the tracing session named 'SESSION' instead of the current | |
112 | tracing session. | |
113 | ||
114 | ||
115 | Snapshot output | |
116 | ~~~~~~~~~~~~~~~ | |
117 | option:-C, option:--ctrl-url='URL':: | |
118 | Set control path URL to 'URL' (must use option:--data-url option | |
119 | also). | |
120 | ||
121 | option:-D, option:--data-url='URL':: | |
122 | Set data path URL to 'URL' (must use option:--ctrl-url option | |
123 | also). | |
124 | ||
125 | option:-m, option:--max-size='SIZE':: | |
126 | Limit the total size of all the snapshot files written when | |
127 | recording a snapshot to 'SIZE' bytes. The `k` (kiB), `M` (MiB), | |
128 | and `G` (GiB) suffixes are supported. | |
129 | ||
130 | option:-n, option:--name='NAME':: | |
131 | Assign the name 'NAME' to the snapshot output. | |
132 | ||
133 | ||
134 | include::common-cmd-help-options.txt[] | |
135 | ||
136 | ||
137 | include::common-cmd-footer.txt[] | |
138 | ||
139 | ||
140 | SEE ALSO | |
141 | -------- | |
7c1a4458 | 142 | man:lttng(1) |