lttng-start(1)

1LTTNG-START(1)                   LTTng Manual                   LTTNG-START(1)
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NAME

6       lttng-start - Start LTTng tracers
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SYNOPSIS

9       lttng [GENERAL OPTIONS] start [SESSION]
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DESCRIPTION

12       The lttng start command starts the various LTTng tracers for a given
13       inactive tracing session.
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15       Starting the LTTng tracers has the effect that all enabled event rules
16       within enabled channels can make their target event sources emit trace
17       events. Whether they are recorded to the local file system, sent over
18       the network, or not recorded at all depends on the specific
19       configuration of the tracing session in which tracing is started. See
20       lttng-create(1) for different session modes.
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22       A tracing session with running tracers is said to be active. Active
23       tracing sessions can return to the inactive state using the lttng-
24       stop(1) command.
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26       If SESSION is omitted, the LTTng tracers are started for the current
27       tracing session (see lttng-create(1) for more information about the
28       current tracing session). Otherwise, they are started for the existing
29       tracing session named SESSION. lttng list outputs all the existing
30       tracing sessions (see lttng-list(1)).
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OPTIONS

33       General options are described in lttng(1).
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35   Program information
36       -h, --help
37           Show command help.
38
39           This option, like lttng-help(1), attempts to launch /usr/bin/man to
40           view the command’s man page. The path to the man pager can be
41           overridden by the LTTNG_MAN_BIN_PATH environment variable.
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43       --list-options
44           List available command options.
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ENVIRONMENT VARIABLES

47       LTTNG_ABORT_ON_ERROR
48           Set to 1 to abort the process after the first error is encountered.
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50       LTTNG_HOME
51           Overrides the $HOME environment variable. Useful when the user
52           running the commands has a non-writable home directory.
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54       LTTNG_MAN_BIN_PATH
55           Absolute path to the man pager to use for viewing help information
56           about LTTng commands (using lttng-help(1) or lttng COMMAND --help).
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58       LTTNG_SESSION_CONFIG_XSD_PATH
59           Path in which the session.xsd session configuration XML schema may
60           be found.
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62       LTTNG_SESSIOND_PATH
63           Full session daemon binary path.
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65           The --sessiond-path option has precedence over this environment
66           variable.
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68       Note that the lttng-create(1) command can spawn an LTTng session daemon
69       automatically if none is running. See lttng-sessiond(8) for the
70       environment variables influencing the execution of the session daemon.
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FILES

73       $LTTNG_HOME/.lttngrc
74           User LTTng runtime configuration.
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76           This is where the per-user current tracing session is stored
77           between executions of lttng(1). The current tracing session can be
78           set with lttng-set-session(1). See lttng-create(1) for more
79           information about tracing sessions.
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81       $LTTNG_HOME/lttng-traces
82           Default output directory of LTTng traces. This can be overridden
83           with the --output option of the lttng-create(1) command.
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85       $LTTNG_HOME/.lttng
86           User LTTng runtime and configuration directory.
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88       $LTTNG_HOME/.lttng/sessions
89           Default location of saved user tracing sessions (see lttng-save(1)
90           and lttng-load(1)).
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92       /usr/local/etc/lttng/sessions
93           System-wide location of saved tracing sessions (see lttng-save(1)
94           and lttng-load(1)).
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96           Note
97           $LTTNG_HOME defaults to $HOME when not explicitly set.
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EXIT STATUS

100       0
101           Success
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103       1
104           Command error
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106       2
107           Undefined command
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109       3
110           Fatal error
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112       4
113           Command warning (something went wrong during the command)
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BUGS

116       If you encounter any issue or usability problem, please report it on
117       the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-tools>.
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RESOURCES

120       •   LTTng project website <https://lttng.org>
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122       •   LTTng documentation <https://lttng.org/docs>
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124       •   Git repositories <http://git.lttng.org>
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126       •   GitHub organization <http://github.com/lttng>
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128       •   Continuous integration <http://ci.lttng.org/>
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130       •   Mailing list <http://lists.lttng.org> for support and development:
131           lttng-dev@lists.lttng.org
132
133       •   IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
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COPYRIGHTS

136       This program is part of the LTTng-tools project.
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138       LTTng-tools is distributed under the GNU General Public License version
139       2 <http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html>. See the
140       LICENSE <https://github.com/lttng/lttng-tools/blob/master/LICENSE> file
141       for details.
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THANKS

144       Special thanks to Michel Dagenais and the DORSAL laboratory
145       <http://www.dorsal.polymtl.ca/> at École Polytechnique de Montréal for
146       the LTTng journey.
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148       Also thanks to the Ericsson teams working on tracing which helped us
149       greatly with detailed bug reports and unusual test cases.
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