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: 5345).
 156
 157 option:-a, option:--apps-sock='PATH'::
 158     Set application Unix socket path to 'PATH'.
 159
 160 option:-c, 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_APP_SOCKET_TIMEOUT`::
 228     Application socket's timeout (seconds) when sending/receiving
 229     commands. After this period of time, the application is unregistered
 230     by the session daemon. A value of 0 or -1 means an infinite timeout.
 231     Default value: 5.
 232
 233 `LTTNG_CONSUMERD32_BIN`::
 234     32-bit consumer daemon binary path.
 235 +
 236 The option:--consumerd32-path option overrides this variable.
 237
 238 `LTTNG_CONSUMERD32_LIBDIR`::
 239     32-bit consumer daemon library path.
 240 +
 241 The option:--consumerd32-libdir option overrides this variable.
 242
 243 `LTTNG_CONSUMERD64_BIN`::
 244     64-bit consumer daemon binary path.
 245 +
 246 The option:--consumerd64-path option overrides this variable.
 247
 248 `LTTNG_CONSUMERD64_LIBDIR`::
 249     64-bit consumer daemon library path.
 250 +
 251 The option:--consumerd64-libdir option overrides this variable.
 252
 253 `LTTNG_DEBUG_NOCLONE`::
 254     Set to 1 to disable the use of `clone()`/`fork()`. Setting this
 255     variable is considered insecure, but it is required to allow
 256     debuggers to work with the session daemon on some operating systems.
 257
 258 `LTTNG_EXTRA_KMOD_PROBES`::
 259     Load specific LTTng Linux kernel modules when kernel tracing
 260     is enabled (option:--no-kernel option is :not: specified), in
 261     addition to loading the default list of LTTng kernel modules.
 262 +
 263 The option:--extra-kmod-probes option overrides this variable.
 264
 265 `LTTNG_KMOD_PROBES`::
 266     Only load specific LTTng Linux kernel modules when kernel tracing
 267     is enabled (option:--no-kernel option is :not: specified).
 268 +
 269 The option:--kmod-probes option overrides this variable.
 270
 271 `LTTNG_NETWORK_SOCKET_TIMEOUT`::
 272     Socket connection, receive and send timeout (milliseconds). A value
 273     of 0 or -1 uses the timeout of the operating system (default).
 274
 275 `LTTNG_SESSION_CONFIG_XSD_PATH`::
 276     Tracing session configuration XML schema definition (XSD) path.
 277
 278
 279 FILES
 280 -----
 281 `$LTTNG_HOME/.lttng`::
 282     User LTTng runtime and configuration directory.
 283
 284 `$LTTNG_HOME/lttng-traces`::
 285     Default output directory of LTTng traces. This can be overridden
 286     with the nloption:--output option of the man:lttng-create(1)
 287     command.
 288
 289 `$LTTNG_HOME/.lttng/sessions/auto`::
 290     Directory from which user tracing configuration files are
 291     automatically loaded when the session daemon starts (see
 292     man:lttng-save(1) and man:lttng-load(1) for saving
 293     and loading tracing sessions).
 294
 295 +{system_sessions_auto_dir}+::
 296     Directory from which system-wide tracing configuration files are
 297     automatically loaded when the session daemon starts (see
 298     man:lttng-save(1) and man:lttng-load(1) for saving
 299     and loading tracing sessions).
 300
 301 `$LTTNG_HOME/.lttng/lttng.conf`::
 302     Default location of the session daemon configuration file (see the
 303     option:--config option).
 304
 305 +{system_lttng_conf}+::
 306     System-wide location of the session daemon configuration file (see
 307     the option:--config option).
 308
 309 NOTE: `$LTTNG_HOME` defaults to `$HOME` when not explicitly set.
 310
 311
 312 EXIT STATUS
 313 -----------
 314 *0*::
 315     Success
 316
 317 *1*::
 318     Error
 319
 320 *3*::
 321     Fatal error
 322
 323
 324 LIMITATIONS
 325 -----------
 326 For an unprivileged user running `lttng-sessiond`, the maximum number of
 327 file descriptors per process is usually 1024. This limits the number of
 328 traceable applications, since for each instrumented application, there
 329 is two file descriptors per CPU and one more socket for bidirectional
 330 communication.
 331
 332 For the root user, the limit is bumped to 65535. A future version will
 333 deal with this limitation.
 334
 335
 336 include::common-footer.txt[]
 337
 338
 339 SEE ALSO
 340 --------
 341 man:lttng(1),
 342 man:lttng-relayd(8),
 343 man:lttng-crash(1),
 344 man:lttng-ust(3),
 345 man:babeltrace(1)