Provided by: lttng-tools_2.13.9-1build1_amd64 
NAME
lttng-enable-event - Create or enable LTTng recording event rules
SYNOPSIS
Create or enable one or more recording event rules to match Linux kernel tracepoint or
system call events:
lttng [GENERAL OPTIONS] enable-event --kernel [--tracepoint | --syscall]
(--all | NAME[,NAME]...) [--filter=EXPR]
[--session=SESSION] [--channel=CHANNEL]
Create or enable a recording event rule to match Linux kernel events created from a
dynamic instrumentation point:
lttng [GENERAL OPTIONS] enable-event --kernel
(--probe=LOC | --function=LOC | --userspace-probe=LOC) RECORDNAME
[--session=SESSION] [--channel=CHANNEL]
Create or enable one or more recording event rules to match user space tracepoint events:
lttng [GENERAL OPTIONS] enable-event --userspace [--tracepoint]
(--all | NAME[,NAME]...) [--exclude=XNAME[,XNAME]...]
[--loglevel=LOGLEVEL | --loglevel-only=LOGLEVEL] [--filter=EXPR]
[--session=SESSION] [--channel=CHANNEL]
Create or enable one or more recording event rules to match Java/Python logging events:
lttng [GENERAL OPTIONS] enable-event (--jul | --log4j | --python)
[--tracepoint] (--all | NAME[,NAME]...)
[--loglevel=LOGLEVEL | --loglevel-only=LOGLEVEL] [--filter=EXPR]
[--session=SESSION] [--channel=CHANNEL]
DESCRIPTION
The lttng enable-event command does one of:
• Create one or more recording event rules.
• Enable one or more disabled recording event rules.
See the “Enable a disabled recording event rule” section below.
See lttng-concepts(7) to learn more about instrumentation points, events, recording event
rules, and event records.
The recording event rule(s) to create or enable belong to:
With the --session=SESSION option
The recording session named SESSION.
Without the --session option
The current recording session (see lttng-concepts(7) to learn more about the current
recording session).
With the --channel=CHANNEL option
The channel named CHANNEL.
Without the --channel option
The channel named channel0.
If there’s already a channel for the selected recording session and domain which isn’t
named channel0, the enable-event command fails. Otherwise, it automatically creates
it.
See the “EXAMPLES” section below for usage examples.
List the recording event rules of a specific recording session and/or channel with the
lttng-list(1) and lttng-status(1) commands.
Disable an enabled recording event rule with the lttng-disable-event(1) command.
Overview of recording event rule conditions
For LTTng to emit and record an event E, E must satisfy all the conditions of a recording
event rule ER, that is:
Explicit conditions
You set the following conditions when you create or enable ER with the enable-event
command:
• The instrumentation point type from which LTTng creates E has a specific type.
See the “Instrumentation point type condition” section below.
• A pattern matches the name of E while another pattern doesn’t.
See the “Event name condition” section below.
• The log level of the instrumentation point from which LTTng creates E is at least
as severe as some value, or is exactly some value.
See the “Instrumentation point log level condition” section below.
• The fields of the payload of E and the current context fields satisfy a filter
expression.
See the “Event payload and context filter condition” section below.
Implicit conditions
• ER itself is enabled.
A recording event rule is enabled on creation.
Enable a disabled recording event rule with the enable-event command.
• The channel to which ER is attached is enabled.
A channel is enabled on creation.
Enable a disabled channel with the lttng-enable-channel(1) command.
• The recording session of ER is active (started).
A recording session is inactive (stopped) on creation.
Start an inactive recording session with the lttng-start(1) command.
• The process for which LTTng creates E is allowed to record events.
All processes are allowed to record events on recording session creation.
Use the lttng-track(1) and lttng-untrack(1) commands to select which processes are
allowed to record events based on specific process attributes.
The dedicated command-line options of most conditions are optional: if you don’t specify
the option, the associated condition is always satisfied.
Instrumentation point type condition
An event E satisfies the instrumentation point type condition of a recording event rule if
the instrumentation point from which LTTng creates E is:
For the Linux kernel tracing domain (--kernel option)
With the --tracepoint option or without any other instrumentation point type option
An LTTng kernel tracepoint, that is, a statically defined point in the source code
of the kernel image or of a kernel module with LTTng kernel tracer macros.
As of LTTng 2.13.9, this is the default instrumentation point type of the Linux
kernel tracing domain, but this may change in the future.
List the available Linux kernel tracepoints with lttng list --kernel. See lttng-
list(1) to learn more.
With the --syscall option
The entry and exit of a Linux kernel system call.
List the available Linux kernel system call instrumentation points with lttng list
--kernel --syscall. See lttng-list(1) to learn more.
With the --probe option
A Linux kprobe, that is, a single probe dynamically placed in the compiled kernel
code.
The argument of the --probe option is the location of the kprobe to insert, either
a symbol or a memory address, while RECORDNAME is the name of the record of E (see
the “Event record name” section below).
The payload of a Linux kprobe event is empty.
With the --userspace-probe option
A Linux user space probe, that is, a single probe dynamically placed at the entry
of a compiled user space application/library function through the kernel.
The argument of the --userspace-probe option is the location of the user space
probe to insert, one of:
• A path and symbol (ELF method).
• A path, provider name, and probe name (SystemTap User-level Statically Defined
Tracing (USDT) method; a DTrace-style marker).
As of LTTng 2.13.9, LTTng only supports USDT probes which are NOT
reference-counted.
RECORDNAME is the name of the record of E (see the “Event record name” section
below).
The payload of a Linux user space probe event is empty.
With the --function option
A Linux kretprobe, that is, two probes dynamically placed at the entry and exit of
a function in the compiled kernel code.
The argument of the --function option is the location of the Linux kretprobe to
insert, either a symbol or a memory address, while RECORDNAME is the name of the
record of E (see the “Event record name” section below).
The payload of a Linux kretprobe event is empty.
For the user space tracing domain (--userspace option)
With or without the --tracepoint option
An LTTng user space tracepoint, that is, a statically defined point in the source
code of a C/C++ application/library with LTTng user space tracer macros.
As of LTTng 2.13.9, this is the default and sole instrumentation point type of the
user space tracing domain, but this may change in the future.
List the available user space tracepoints with lttng list --userspace. See lttng-
list(1) to learn more.
For the java.util.logging (--jul option), Apache log4j (--log4j option), and Python
(--python option) tracing domains
With or without the --tracepoint option
A logging statement.
As of LTTng 2.13.9, this is the default and sole instrumentation point type of the
java.util.logging, Apache log4j, and Python tracing domains, but this may change
in the future.
List the available Java and Python loggers with lttng list --jul, lttng list
--log4j, and lttng list --python. See lttng-list(1) to learn more.
Event name condition
An event E satisfies the event name condition of a recording event rule ER if the two
following statements are true:
• You specify the --all option or, depending on the instrumentation type condition (see
the “Instrumentation point type condition” section above) of ER, NAME matches:
LTTng tracepoint
The full name of the tracepoint from which LTTng creates E.
Note that the full name of a user space tracepoint is PROVIDER:NAME, where
PROVIDER is the tracepoint provider name and NAME is the tracepoint name.
Logging statement
The name of the Java or Python logger from which LTTng creates E.
Linux system call
The name of the system call, without any sys_ prefix, from which LTTng creates E.
• You don’t specify the --exclude=XNAME[,XNAME]... option or, depending on the
instrumentation type condition of ER, none of the XNAME arguments matches the full
name of the user space tracepoint from which LTTng creates E.
The --exclude option is only available with the --userspace option.
This condition is only meaningful for the LTTng tracepoint, logging statement, and Linux
system call instrumentation point types: it’s always satisfied for the other types.
In all cases, NAME and XNAME are globbing patterns: the * character means “match
anything”. To match a literal * character, use \*. To match a literal , character, use \,.
Important
Make sure to single-quote NAME and XNAME when they contain the * character and when
you run the enable-event command from a shell.
With the LTTng tracepoint, logging statement, and Linux system call instrumentation point
types, the enable-event command creates or enables one independent recording event rule
per NAME argument (non-option, comma-separated). With the --all option, the enable-event
command creates or enables a single recording event rule.
Instrumentation point log level condition
An event E satisfies the instrumentation point log level condition of a recording event
rule if either:
• The --loglevel and --loglevel-only options are missing.
• The log level of the LTTng user space tracepoint or logging statement which creates E
is:
With the --loglevel=LOGLEVEL option
At least as severe as LOGLEVEL.
With the --loglevel-only=LOGLEVEL option
Exactly LOGLEVEL.
This condition is only meaningful for the LTTng user space tracepoint and logging
statement instrumentation point types: it’s always satisfied for other types.
The available values of LOGLEVEL are, depending on the tracing domain, from the most to
the least severe:
User space (--userspace option)
• EMERG (0)
• ALERT (1)
• CRIT (2)
• ERR (3)
• WARNING (4)
• NOTICE (5)
• INFO (6)
• DEBUG_SYSTEM (7)
• DEBUG_PROGRAM (8)
• DEBUG_PROCESS (9)
• DEBUG_MODULE (10)
• DEBUG_UNIT (11)
• DEBUG_FUNCTION (12)
• DEBUG_LINE (13)
• DEBUG (14)
java.util.logging (--jul option)
• OFF (INT32_MAX)
• SEVERE (1000)
• WARNING (900)
• INFO (800)
• CONFIG (700)
• FINE (500)
• FINER (400)
• FINEST (300)
• ALL (INT32_MIN)
Apache log4j (--log4j option)
• OFF (INT32_MAX)
• FATAL (50000)
• ERROR (40000)
• WARN (30000)
• INFO (20000)
• DEBUG (10000)
• TRACE (5000)
• ALL (INT32_MIN)
Python (--python option)
• CRITICAL (50)
• ERROR (40)
• WARNING (30)
• INFO (20)
• DEBUG (10)
• NOTSET (0)
Event payload and context filter condition
An event E satisfies the event payload and context filter condition of a recording event
rule if the --filter=EXPR option is missing or if EXPR is true.
This condition is only meaningful for the LTTng tracepoint and Linux system call
instrumentation point types: it’s always satisfied for other types.
EXPR can contain references to the payload fields of E and to the current context fields.
Important
Make sure to single-quote EXPR when you run the enable-event command from a shell, as
filter expressions typically include characters having a special meaning for most
shells.
The expected syntax of EXPR is similar to the syntax of a C language conditional
expression (an expression which an if statement can evaluate), but there are a few
differences:
• A NAME expression identifies an event payload field named NAME (a C identifier).
Use the C language dot and square bracket notations to access nested structure and
array/sequence fields. You can only use a constant, positive integer number within
square brackets. If the index is out of bounds, EXPR is false.
The value of an enumeration field is an integer.
When a field expression doesn’t exist, EXPR is false.
Examples: my_field, target_cpu, seq[7], msg.user[1].data[2][17].
• A $ctx.TYPE expression identifies the statically-known context field having the type
TYPE (a C identifier).
List the available statically-known context field names with the lttng-add-context(1)
command.
When a field expression doesn’t exist, EXPR is false.
Examples: $ctx.prio, $ctx.preemptible, $ctx.perf:cpu:stalled-cycles-frontend.
• A $app.PROVIDER:TYPE expression identifies the application-specific context field
having the type TYPE (a C identifier) from the provider PROVIDER (a C identifier).
When a field expression doesn’t exist, EXPR is false.
Example: $app.server:cur_user.
• Compare strings, either string fields or string literals (double-quoted), with the ==
and != operators.
When comparing to a string literal, the * character means “match anything”. To match a
literal * character, use \*.
Examples: my_field == "user34", my_field == my_other_field, my_field == "192.168.*".
• The precedence table of the operators which are supported in EXPR is as follows. In
this table, the highest precedence is 1:
┌───────────┬──────────┬─────────────────────┬───────────────┐
│Precedence │ Operator │ Description │ Associativity │
├───────────┼──────────┼─────────────────────┼───────────────┤
│1 │ - │ Unary minus │ Right-to-left │
├───────────┼──────────┼─────────────────────┼───────────────┤
│1 │ + │ Unary plus │ Right-to-left │
├───────────┼──────────┼─────────────────────┼───────────────┤
│1 │ ! │ Logical NOT │ Right-to-left │
├───────────┼──────────┼─────────────────────┼───────────────┤
│1 │ ~ │ Bitwise NOT │ Right-to-left │
├───────────┼──────────┼─────────────────────┼───────────────┤
│2 │ << │ Bitwise left shift │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│2 │ >> │ Bitwise right shift │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│3 │ & │ Bitwise AND │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│4 │ ^ │ Bitwise XOR │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│5 │ | │ Bitwise OR │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│6 │ < │ Less than │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│6 │ <= │ Less than or equal │ Left-to-right │
│ │ │ to │ │
├───────────┼──────────┼─────────────────────┼───────────────┤
│6 │ > │ Greater than │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│6 │ >= │ Greater than or │ Left-to-right │
│ │ │ equal to │ │
├───────────┼──────────┼─────────────────────┼───────────────┤
│7 │ == │ Equal to │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│7 │ != │ Not equal to │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│8 │ && │ Logical AND │ Left-to-right │
├───────────┼──────────┼─────────────────────┼───────────────┤
│9 │ || │ Logical OR │ Left-to-right │
└───────────┴──────────┴─────────────────────┴───────────────┘
Parentheses are supported to bypass the default order.
Important
Unlike the C language, the bitwise AND and OR operators (& and |) in EXPR take
precedence over relational operators (<, <=, >, >=, ==, and !=). This means the
expression 2 & 2 == 2 is true while the equivalent C expression is false.
The arithmetic operators are NOT supported.
LTTng first casts all integer constants and fields to signed 64-bit integers. The
representation of negative integers is two’s complement. This means that, for example,
the signed 8-bit integer field 0xff (-1) becomes 0xffffffffffffffff (still -1) once
casted.
Before a bitwise operator is applied, LTTng casts all its operands to unsigned 64-bit
integers, and then casts the result back to a signed 64-bit integer. For the bitwise
NOT operator, it’s the equivalent of this C expression:
(int64_t) ~((uint64_t) val)
For the binary bitwise operators, it’s the equivalent of those C expressions:
(int64_t) ((uint64_t) lhs >> (uint64_t) rhs)
(int64_t) ((uint64_t) lhs << (uint64_t) rhs)
(int64_t) ((uint64_t) lhs & (uint64_t) rhs)
(int64_t) ((uint64_t) lhs ^ (uint64_t) rhs)
(int64_t) ((uint64_t) lhs | (uint64_t) rhs)
If the right-hand side of a bitwise shift operator (<< and >>) is not in the [0, 63]
range, then EXPR is false.
Note
Use the lttng-track(1) and lttng-untrack(1) commands to allow or disallow processes to
record LTTng events based on their attributes instead of using equivalent
statically-known context fields in EXPR like $ctx.pid.
The former method is much more efficient.
EXPR examples:
msg_id == 23 && size >= 2048
$ctx.procname == "lttng*" && (!flag || poel < 34)
$app.my_provider:my_context == 17.34e9 || some_enum >= 14
$ctx.cpu_id == 2 && filename != "*.log"
eax_reg & 0xff7 == 0x240 && x[4] >> 12 <= 0x1234
Event record name
When LTTng records an event E, the resulting event record has a name which depends on the
instrumentation point type condition (see the “Instrumentation point type condition”
section above) of the recording event rule which matched E:
LTTng tracepoint (--kernel/--userspace and --tracepoint options)
Full name of the tracepoint from which LTTng creates E.
Note that the full name of a user space tracepoint is PROVIDER:NAME, where PROVIDER is
the tracepoint provider name and NAME is the tracepoint name.
java.util.logging logging statement (--jul and --tracepoint options)
lttng_jul:event
Such an event record has a string field logger_name which contains the name of the
java.util.logging logger from which LTTng creates E.
Apache log4j logging statement (--log4j and --tracepoint options)
lttng_log4j:event
Such an event record has a string field logger_name which contains the name of the
Apache log4j logger from which LTTng creates E.
Python logging statement (--python and --tracepoint options)
lttng_python:event
Such an event record has a string field logger_name which contains the name of the
Python logger from which LTTng creates E.
Linux system call (--kernel and --syscall options)
Entry
syscall_entry_NAME, where NAME is the name of the system call from which LTTng
creates E, without any sys_ prefix.
Exit
syscall_exit_NAME, where NAME is the name of the system call from which LTTng
creates E, without any sys_ prefix.
Linux kprobe (--kernel and --probe options), Linux user space probe (--kernel and
--userspace-probe options)
RECORDNAME (first non-option argument).
Linux kretprobe (--kernel and --function options)
Entry
RECORDNAME_entry
Exit
RECORDNAME_exit
Enable a disabled recording event rule
The enable-event command can enable a disabled recording event rule, as listed in the
output of the lttng-list(1) command.
You may enable a disabled recording event rule regardless of the activity (started or
stopped) of its recording session (see lttng-start(1) and lttng-stop(1)).
To enable a disabled recording event rule, run the enable-event command with the exact
same options and arguments that you used to create it. In particular, with the
--filter=EXPR option, EXPR must be the exact same string as the one you used on creation.
OPTIONS
See lttng(1) for GENERAL OPTIONS.
Tracing domain
One of:
-j, --jul
Create or enable recording event rules in the java.util.logging (JUL) tracing domain.
-k, --kernel
Create or enable recording event rules in the Linux kernel tracing domain.
-l, --log4j
Create or enable recording event rules in the Apache log4j tracing domain.
-p, --python
Create or enable recording event rules in the Python tracing domain.
-u, --userspace
Create or enable recording event rules in the user space tracing domain.
Recording target
-c CHANNEL, --channel=CHANNEL
Create or enable recording event rules attached to the channel named CHANNEL instead
of channel0.
-s SESSION, --session=SESSION
Create or enable recording event rules in the recording session named SESSION instead
of the current recording session.
Instrumentation point type condition
See the “Instrumentation point type condition” section above.
At most one of:
--function=LOC
Only match Linux kretprobe events.
Only available with the --kernel option.
LOC is one of:
• A function address (0x hexadecimal prefix supported).
• A function symbol name.
• A function symbol name and an offset (SYMBOL+OFFSET format).
You must specify the event record name with RECORDNAME. See the “Event record name”
section above to learn more.
--probe=LOC
Only match Linux kprobe events.
Only available with the --kernel option.
LOC is one of:
• An address (0x hexadecimal prefix supported).
• A symbol name.
• A symbol name and an offset (SYMBOL+OFFSET format).
You must specify the event record name with RECORDNAME. See the “Event record name”
section above to learn more.
--userspace-probe=LOC
Only match Linux user space probe events.
Only available with the --kernel option.
LOC is one of:
[elf:]PATH:SYMBOL
Probe an available symbol within a user space application or library.
PATH
Application or library path.
One of:
• An absolute path.
• A relative path.
• The name of an application as found in the directories listed in the PATH
environment variable.
SYMBOL
Symbol name of the function of which to instrument the entry.
SYMBOL can be any defined code symbol in the output of the nm(1) command,
including with its --dynamic option, which lists dynamic symbols.
As of LTTng 2.13.9, not specifying elf: is equivalent to specifying it, but this
default may change in the future.
Examples:
• --userspace-probe=/usr/lib/libc.so.6:malloc
• --userspace-probe=./myapp:createUser
• --userspace-probe=elf:httpd:ap_run_open_htaccess
sdt:PATH:PROVIDER:NAME
Use a SystemTap User-level Statically Defined Tracing (USDT) probe within a user
space application or library.
PATH
Application or library path.
This can be:
• An absolute path.
• A relative path.
• The name of an application as found in the directories listed in the PATH
environment variable.
PROVIDER, NAME
USDT provider and probe names.
For example, with the following USDT probe:
DTRACE_PROBE2("server", "accept_request",
request_id, ip_addr);
The provider/probe name pair is server:accept_request.
Example: --userspace-probe=sdt:./build/server:server:accept_request
You must specify the event record name with RECORDNAME. See the “Event record name”
section above to learn more.
--syscall
Only match Linux system call events.
Only available with the --kernel option.
--tracepoint
Only match:
With the --kernel or --userspace option
LTTng tracepoint events.
With the --jul, --log4j, or --python option
Logging events.
With the --kernel, not specifying any of the instrumentation point type options is
equivalent to specifying the --tracepoint option, but this default may change in the
future.
With the --userspace, --jul, --log4j, and --python options, not specifying the
--tracepoint option is equivalent to specifying it, but this default may change in the
future.
Event name condition
See the “Event name condition” section above.
-a, --all
Equivalent to a single NAME argument (LTTng tracepoint or logger name) set to * (match
anything).
You may NOT use this option with a NAME argument.
-x XNAME[,XNAME]..., --exclude=XNAME[,XNAME]...
Only match events of which none of the XNAME arguments matches the full name of the
LTTng user space tracepoint.
Only available with the --userspace option.
XNAME is a globbing pattern: the * character means “match anything”. To match a
literal * character, use \*. To match a literal , character, use \,.
Instrumentation point log level condition
See the “Instrumentation point log level condition” section above.
At most one of:
--loglevel=LOGLEVEL
Only match events of which the log level of the LTTng tracepoint or logging statement
is at least as severe as LOGLEVEL.
--loglevel-only=LOGLEVEL
Only match events of which the log level of the LTTng tracepoint or logging statement
is exactly LOGLEVEL.
The instrumentation point log level options above are NOT available with the --kernel
option.
Event payload and context filter condition
See the “Event payload and context filter condition” section above.
-f EXPR, --filter=EXPR
Only match events of which EXPR, which can contain references to event payload and
current context fields, is true.
This option is only available with the --tracepoint or --syscall option.
Program information
-h, --help
Show help.
This option attempts to launch /usr/bin/man to view this manual page. Override the
manual pager path with the LTTNG_MAN_BIN_PATH environment variable.
--list-options
List available command options and quit.
EXIT STATUS
0
Success
1
Command error
2
Undefined command
3
Fatal error
4
Command warning (something went wrong during the command)
ENVIRONMENT
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is encountered.
LTTNG_HOME
Path to the LTTng home directory.
Defaults to $HOME.
Useful when the Unix user running the commands has a non-writable home directory.
LTTNG_MAN_BIN_PATH
Absolute path to the manual pager to use to read the LTTng command-line help (with
lttng-help(1) or with the --help option) instead of /usr/bin/man.
LTTNG_SESSION_CONFIG_XSD_PATH
Path to the directory containing the session.xsd recording session configuration XML
schema.
LTTNG_SESSIOND_PATH
Absolute path to the LTTng session daemon binary (see lttng-sessiond(8)) to spawn from
the lttng-create(1) command.
The --sessiond-path general option overrides this environment variable.
FILES
$LTTNG_HOME/.lttngrc
Unix user’s LTTng runtime configuration.
This is where LTTng stores the name of the Unix user’s current recording session
between executions of lttng(1). lttng-create(1) and lttng-set-session(1) set the
current recording session.
$LTTNG_HOME/lttng-traces
Default output directory of LTTng traces in local and snapshot modes.
Override this path with the --output option of the lttng-create(1) command.
$LTTNG_HOME/.lttng
Unix user’s LTTng runtime and configuration directory.
$LTTNG_HOME/.lttng/sessions
Default directory containing the Unix user’s saved recording session configurations
(see lttng-save(1) and lttng-load(1)).
/etc/lttng/sessions
Directory containing the system-wide saved recording session configurations (see
lttng-save(1) and lttng-load(1)).
Note
$LTTNG_HOME defaults to the value of the HOME environment variable.
EXAMPLES
Example 1. Create a recording event rule which matches all Linux system call events
(current recording session, default channel).
See the --all and --syscall options.
$ lttng enable-event --kernel --all --syscall
Example 2. Create a recording event rule which matches user space tracepoint events named
specifically (current recording session, default channel).
The recording event rule below matches all user space tracepoint events of which the
name starts with my_provider:msg.
$ lttng enable-event --userspace 'my_provider:msg*'
Example 3. Create three recording event rules which match Python logging events named
specifically (current recording session, default channel).
$ lttng enable-event --python server3,ui.window,user-mgmt
Example 4. Create a recording event rule which matches Apache log4j logging events with a
specific log level range (current recording session, specific channel).
See the --channel, --all, and --loglevel options.
$ lttng enable-event --log4j --channel=my-loggers \
--all --loglevel=INFO
Example 5. Create a recording event rule which matches specific Linux kprobe events
(current recording session, default channel).
The recording event rule below matches the entry of usb_disconnect() Linux kernel
function calls. The records of such events are named usbd (see the “Event record name”
section above).
See the --probe option.
$ lttng enable-event --kernel --probe=usb_disconnect usbd
Example 6. Create a recording event rule which matches Linux kernel tracepoint events
which satisfy an event payload and context filter (specific recording session, default
channel).
See the --session and --filter options.
$ lttng enable-event --kernel --session=my-session 'sched_*' \
--filter='$ctx.preemptible && comm != "systemd*"'
Example 7. Enable two Linux kernel tracepoint recording event rules (current recording
session, specific channel).
See the --channel option.
$ lttng enable-event --kernel --channel=tva ja,wendy
RESOURCES
• LTTng project website <https://lttng.org>
• LTTng documentation <https://lttng.org/docs>
• LTTng bug tracker <https://bugs.lttng.org>
• Git repositories <https://git.lttng.org>
• GitHub organization <https://github.com/lttng>
• Continuous integration <https://ci.lttng.org/>
• Mailing list <https://lists.lttng.org/> for support and development: lttng-
dev@lists.lttng.org
• IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
COPYRIGHT
This program is part of the LTTng-tools project.
LTTng-tools is distributed under the GNU General Public License version 2
<http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html>. See the LICENSE
<https://github.com/lttng/lttng-tools/blob/master/LICENSE> file for details.
THANKS
Special thanks to Michel Dagenais and the DORSAL laboratory
<http://www.dorsal.polymtl.ca/> at École Polytechnique de Montréal for the LTTng journey.
Also thanks to the Ericsson teams working on tracing which helped us greatly with detailed
bug reports and unusual test cases.
SEE ALSO
lttng(1), lttng-disable-event(1), lttng-enable-channel(1), lttng-list(1), lttng-start(1),
lttng-track(1), lttng-concepts(7)