doc/man/lttng-sessiond.8.txt

   1 lttng-sessiond(8)
   2 =================
   3
   4
   5 NAME
   6 ----
   7 lttng-sessiond - LTTng 2 tracing session daemon
   8
   9
  10 SYNOPSIS
  11 --------
  12 [verse]
  13 *lttng-sessiond* [option:--background | option:--daemonize] [option:--sig-parent]
  14                [option:--config='PATH'] [option:--group='GROUP'] [option:--load='PATH']
  15                [option:--agent-tcp-port='PORT']
  16                [option:--apps-sock='PATH'] [option:--client-sock='PATH']
  17                [option:--no-kernel | [option:--kmod-probes='PROBE'[,'PROBE']...]
  18                               [option:--extra-kmod-probes='PROBE'[,'PROBE']...]
  19                               [option:--kconsumerd-err-sock='PATH']
  20                               [option:--kconsumerd-cmd-sock='PATH']]
  21                [option:--ustconsumerd32-err-sock='PATH']
  22                [option:--ustconsumerd64-err-sock='PATH']
  23                [option:--ustconsumerd32-cmd-sock='PATH']
  24                [option:--ustconsumerd64-cmd-sock='PATH']
  25                [option:--consumerd32-path='PATH'] [option:--consumerd32-libdir='PATH']
  26                [option:--consumerd64-path='PATH'] [option:--consumerd64-libdir='PATH']
  27                [option:--quiet | [option:-v | option:-vv | option:-vvv] [option:--verbose-consumer]]
  28
  29
  30 DESCRIPTION
  31 -----------
  32 The http://lttng.org/[_Linux Trace Toolkit: next generation_] is an open
  33 source software package used for correlated tracing of the Linux kernel,
  34 user applications, and user libraries.
  35
  36 LTTng consists of Linux kernel modules (for Linux kernel tracing) and
  37 dynamically loaded libraries (for user application and library tracing).
  38
  39 The _LTTng session daemon_ is a tracing registry which allows the user
  40 to interact with multiple tracers (kernel and user space) within the
  41 same container, a _tracing session_. Traces can be gathered from the
  42 Linux kernel and/or from instrumented applications (see
  43 man:lttng-ust(3)). You can aggregate and read the events of LTTng
  44 traces using man:babeltrace(1).
  45
  46 To trace the Linux kernel, the session daemon needs to be running as
  47 `root`. LTTng uses a _tracing group_ to allow specific users to interact
  48 with the root session daemon. The default tracing group name is
  49 `tracing`. You can use the option:--group option to set the tracing
  50 group name to use.
  51
  52 Session daemons can coexist. You can have a session daemon running as
  53 user Alice that can be used to trace her applications alongside a root
  54 session daemon or a session daemon running as user Bob.
  55
  56 The LTTng session daemon manages trace data consumer daemons by spawning
  57 them when necessary. You do not need to manage the consumer daemons
  58 manually.
  59
  60 NOTE: It is highly recommended to start the session daemon at boot time
  61 for stable and long-term tracing.
  62
  63
  64 Automatic loading of tracing session configurations
  65 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  66 When the session daemon starts, it automatically loads session
  67 configuration files.
  68
  69 The following directories are searched, non-recursively, in this order
  70 for configuration files to load on launch:
  71
  72 . `$LTTNG_HOME/.lttng/sessions/auto` (`$LTTNG_HOME` defaults to `$HOME`)
  73 . +{system_sessions_auto_dir}+
  74
  75 Note that both the directory containing the tracing session
  76 configurations _and_ the session daemon binary _must_ share the same UID
  77 for the configurations to be automatically loaded.
  78
  79 The option:--load option overrides the default directories _and_ the UID
  80 check. The session daemon simply checks if the path is accessible and
  81 tries to load every tracing session configuration in it. When this
  82 option is specified, the default directories are :not: searched for
  83 configuration files. When the option is not specified, _both_ default
  84 directories are searched for configuration files.
  85
  86 If the option:--load option's argument is a directory, then all the
  87 tracing session configurations found in all the files in this directory
  88 are loaded. If the argument is a file, then all the tracing session
  89 configurations found in this file are loaded.
  90
  91
  92 OPTIONS
  93 -------
  94 Daemon configuration
  95 ~~~~~~~~~~~~~~~~~~~~
  96 option:-b, option:--background::
  97     Start as Unix daemon, but keep file descriptors (console) open.
  98     Use the option:--daemonize option instead to close the file
  99     descriptors.
 100
 101 option:-d, option:--daemonize::
 102     Start as Unix daemon, and close file descriptors (console). Use the
 103     option:--background option instead to keep the file descriptors
 104     open.
 105
 106 option:-f, option:--config='PATH'::
 107     Load session daemon configuration from path 'PATH'.
 108
 109 option:-g, option:--group='GROUP'::
 110     Use 'GROUP' as Unix tracing group (default: `tracing`).
 111
 112 option:-l, option:--load='PATH'::
 113     Automatically load tracing session configurations from 'PATH',
 114     either a directory or a file, instead of loading them from the
 115     default search directories.
 116
 117 option:-S, option:--sig-parent::
 118     Send `SIGUSR1` to parent process to notify readiness.
 119 +
 120 NOTE: This is used by man:lttng(1) to get notified when the
 121 session daemon is ready to accept commands. When building a third party
 122 tool on liblttng-ctl, this option can be very handy to synchronize the
 123 control tool and the session daemon.
 124
 125
 126 Linux kernel tracing
 127 ~~~~~~~~~~~~~~~~~~~~
 128 option:--extra-kmod-probes='PROBE'[,'PROBE']...::
 129     Load specific LTTng Linux kernel modules when kernel tracing
 130     is enabled (option:--no-kernel option is :not: specified), in
 131     addition to loading the default list of LTTng kernel modules.
 132 +
 133 Only the name of the probe needs to be specified, without the
 134 `lttng-probe-` prefix and without the kernel module extension suffix.
 135 For example, specify `sched` to load the `lttng-probe-sched.ko` kernel
 136 module.
 137
 138 option:--kmod-probes='PROBE'[,'PROBE']...::
 139     Only load specific LTTng Linux kernel modules when kernel tracing
 140     is enabled (option:--no-kernel option is :not: specified).
 141 +
 142 Only the name of the probe needs to be specified, without the
 143 `lttng-probe-` prefix and without the kernel module extension suffix.
 144 For example, specify `sched` to load the `lttng-probe-sched.ko` kernel
 145 module.
 146
 147 option:--no-kernel::
 148     Disable Linux kernel tracing.
 149
 150
 151 Paths and ports
 152 ~~~~~~~~~~~~~~~
 153 option:--agent-tcp-port='PORT'::
 154     Listen on TCP port 'PORT' for agent application registrations
 155     (default: {default_agent_tcp_port}).
 156
 157 option:-a 'PATH', option:--apps-sock='PATH'::
 158     Set application Unix socket path to 'PATH'.
 159
 160 option:-c 'PATH', option:--client-sock='PATH'::
 161     Set client Unix socket path to 'PATH'.
 162
 163 option:--consumerd32-libdir='PATH'::
 164     Set 32-bit consumer daemon library directory to 'PATH'.
 165
 166 option:--consumerd32-path='PATH'::
 167     Set 32-bit consumer daemon binary path to 'PATH'.
 168
 169 option:--consumerd64-libdir='PATH'::
 170     Set 64-bit consumer daemon library directory to 'PATH'.
 171
 172 option:--consumerd64-path='PATH'::
 173     Set 64-bit consumer daemon binary path to 'PATH'.
 174
 175 option:--kconsumerd-cmd-sock='PATH'::
 176     Set Linux kernel consumer daemon's command Unix socket path
 177     to 'PATH'.
 178
 179 option:--kconsumerd-err-sock='PATH'::
 180     Set Linux kernel consumer daemon's error Unix socket path
 181     to 'PATH'.
 182
 183 option:--ustconsumerd32-cmd-sock='PATH'::
 184     Set 32-bit consumer daemon's command Unix socket path to 'PATH'.
 185
 186 option:--ustconsumerd64-cmd-sock='PATH'::
 187     Set 64-bit consumer daemon's command Unix socket path to 'PATH'.
 188
 189 option:--ustconsumerd32-err-sock='PATH'::
 190     Set 32-bit consumer daemon's error Unix socket path to 'PATH'.
 191
 192 option:--ustconsumerd64-err-sock='PATH'::
 193     Set 64-bit consumer daemon's error Unix socket path to 'PATH'.
 194
 195
 196 Verbosity
 197 ~~~~~~~~~
 198 option:-q, option:--quiet::
 199     Suppress all messages, including warnings and errors.
 200
 201 option:-v, option:--verbose::
 202     Increase verbosity.
 203 +
 204 Three levels of verbosity are available, which are triggered by
 205 appending additional `v` letters to the option
 206 (that is, `-vv` and `-vvv`).
 207
 208 option:--verbose-consumer::
 209     Increase verbosity of consumer daemons spawned by this session
 210     daemon.
 211
 212
 213 Program information
 214 ~~~~~~~~~~~~~~~~~~~
 215 option:-h, option:--help::
 216     Show help.
 217
 218 option:-V, option:--version::
 219     Show version.
 220
 221
 222 ENVIRONMENT VARIABLES
 223 ---------------------
 224 Note that command-line options override their equivalent environment
 225 variable.
 226
 227 `LTTNG_ABORT_ON_ERROR`::
 228     Set to 1 to abort the process after the first error is encountered.
 229
 230 `LTTNG_APP_SOCKET_TIMEOUT`::
 231     Application socket's timeout (seconds) when sending/receiving
 232     commands. After this period of time, the application is unregistered
 233     by the session daemon. A value of 0 or -1 means an infinite timeout.
 234     Default value: {default_app_socket_rw_timeout}.
 235
 236 `LTTNG_CONSUMERD32_BIN`::
 237     32-bit consumer daemon binary path.
 238 +
 239 The option:--consumerd32-path option overrides this variable.
 240
 241 `LTTNG_CONSUMERD32_LIBDIR`::
 242     32-bit consumer daemon library path.
 243 +
 244 The option:--consumerd32-libdir option overrides this variable.
 245
 246 `LTTNG_CONSUMERD64_BIN`::
 247     64-bit consumer daemon binary path.
 248 +
 249 The option:--consumerd64-path option overrides this variable.
 250
 251 `LTTNG_CONSUMERD64_LIBDIR`::
 252     64-bit consumer daemon library path.
 253 +
 254 The option:--consumerd64-libdir option overrides this variable.
 255
 256 `LTTNG_DEBUG_NOCLONE`::
 257     Set to 1 to disable the use of `clone()`/`fork()`. Setting this
 258     variable is considered insecure, but it is required to allow
 259     debuggers to work with the session daemon on some operating systems.
 260
 261 `LTTNG_EXTRA_KMOD_PROBES`::
 262     Load specific LTTng Linux kernel modules when kernel tracing
 263     is enabled (option:--no-kernel option is :not: specified), in
 264     addition to loading the default list of LTTng kernel modules.
 265 +
 266 The option:--extra-kmod-probes option overrides this variable.
 267
 268 `LTTNG_KMOD_PROBES`::
 269     Only load specific LTTng Linux kernel modules when kernel tracing
 270     is enabled (option:--no-kernel option is :not: specified).
 271 +
 272 The option:--kmod-probes option overrides this variable.
 273
 274 `LTTNG_NETWORK_SOCKET_TIMEOUT`::
 275     Socket connection, receive and send timeout (milliseconds). A value
 276     of 0 or -1 uses the timeout of the operating system (default).
 277
 278 `LTTNG_SESSION_CONFIG_XSD_PATH`::
 279     Tracing session configuration XML schema definition (XSD) path.
 280
 281
 282 FILES
 283 -----
 284 `$LTTNG_HOME/.lttng`::
 285     User LTTng runtime and configuration directory.
 286
 287 `$LTTNG_HOME/lttng-traces`::
 288     Default output directory of LTTng traces. This can be overridden
 289     with the nloption:--output option of the man:lttng-create(1)
 290     command.
 291
 292 `$LTTNG_HOME/.lttng/sessions/auto`::
 293     Directory from which user tracing configuration files are
 294     automatically loaded when the session daemon starts (see
 295     man:lttng-save(1) and man:lttng-load(1) for saving
 296     and loading tracing sessions).
 297
 298 +{system_sessions_auto_dir}+::
 299     Directory from which system-wide tracing configuration files are
 300     automatically loaded when the session daemon starts (see
 301     man:lttng-save(1) and man:lttng-load(1) for saving
 302     and loading tracing sessions).
 303
 304 `$LTTNG_HOME/.lttng/lttng.conf`::
 305     Default location of the session daemon configuration file (see the
 306     option:--config option).
 307
 308 +{system_lttng_conf}+::
 309     System-wide location of the session daemon configuration file (see
 310     the option:--config option).
 311
 312 NOTE: `$LTTNG_HOME` defaults to `$HOME` when not explicitly set.
 313
 314
 315 EXIT STATUS
 316 -----------
 317 *0*::
 318     Success
 319
 320 *1*::
 321     Error
 322
 323 *3*::
 324     Fatal error
 325
 326
 327 LIMITATIONS
 328 -----------
 329 For an unprivileged user running `lttng-sessiond`, the maximum number of
 330 file descriptors per process is usually 1024. This limits the number of
 331 traceable applications, since for each instrumented application, there
 332 is two file descriptors per CPU and one more socket for bidirectional
 333 communication.
 334
 335 For the root user, the limit is bumped to 65535. A future version will
 336 deal with this limitation.
 337
 338
 339 include::common-footer.txt[]
 340
 341
 342 SEE ALSO
 343 --------
 344 man:lttng(1),
 345 man:lttng-relayd(8),
 346 man:lttng-crash(1),
 347 man:lttng-ust(3),
 348 man:babeltrace(1)