asl.conf(5) BSD File Formats Manual asl.conf(5)
NAME
asl.conf -- configuration file for syslogd(8) and aslmanager(8)
DESCRIPTION
The syslogd(8) server reads the /etc/asl.conf file at startup, and re-
reads the file when it receives a HUP signal. The aslmanager(8) daemon
reads the file when it starts. See the ASLMANAGER PARAMETER SETTINGS
section for details on aslmanager-specific parameters.
If the /etc/asl directory exists, then syslogd and aslmanager will read
each file it contains. These files must have the same format as
asl.conf. Each file configures an independent module, identified by the
file name. Modules may be enabled or disabled independently. Each mod-
ule may specify its own set of rules for acting on received messages.
See the ASL MODULES section for details.
The files contains four types of lines. Each type is identified by the
first non-whitespace character.
= Parameter settings
? Query-action rules
> Output file or directory configuration options
# Comments
Parameter setting lines in the configuration file are generally of the
form:
= parameter_name value ...
Most parameter settings require a single value, although some may take
several values. See the PARAMETER SETTINGS section for details.
Query-action rules in the file generally have the form:
? query action ...
This directs syslogd to perform the specified action when a received mes-
sage matches the given query. Actions may be followed by optional argu-
ments. See the QUERY-ACTION RULES section for details.
Most query-action rules specify output files or ASL-format data stores
where matching messages should be saved. The optional parameters for
those rules can specify a number of options for these outputs. As a con-
venience, these configuration options may be specified on a separate
line. Output configuration settings in the file begin with a greater-
than sign ``>'' followed by a file or ASL directory name and the configu-
ration options for that file or directory. These lines generally have
the form:
> filename option ...
See the OUTPUT CONFIGURATION SETTINGS section for details.
Comments lines are ignored.
PARAMETER SETTINGS
The following parameter-settings are recognized by syslogd.
debug Enables or disables internal debugging output.
This is probably of little interest to most
users. The debug parameter requires a value of
``1'' to enable debug output, or a value of ``0''
to disable it. Debugging messages are written to
/var/log/syslogd.log.
mark_time Sets the time interval for the mark facility.
The default is 0 seconds, which indicates that
mark messages are not generated.
dup_delay Sets the maximum time before writing a ``last
message repeated <N> times'' message in a log
file when duplicate messages have been detected.
The default is 30 seconds.
utmp_ttl Sets the time-to-live for messages used by the
utmp, wtmp, and lastlog subsystems. The default
is 31622400 seconds (approximately 1 year).
mps_limit Sets the kernel message per second quota. The
default is value is 500. A value of 0 disables
the quota mechanism. Note that this setting only
limits the number of kernel messages that will be
saved by syslogd. User processes are limited to
36000 messages per hour. The limit for a user
process is not enforced if a remote-control ASL
filter is in place for the process. See the
syslog(1) manual for enabling a remote-control
filter using the -c option with the syslog com-
mand.
max_file_size Sets the maximum file size for individual files
in the ASL database. The default is 25600000
bytes.
QUERY-ACTION RULES
Query-action rules are used to cause syslogd to perform specific actions
when received messages match a specified query pattern. For example, to
save certain messages in a file. The rules are processed in the order in
which they appear in the file. This matters because some actions can
affect further processing. For example, an ``ignore'' action causes
syslogd to stop processing the rules in a file for messages that match a
given query pattern.
Query-action rules contain three components: a query, an action, and
optional parameters specific to that action. For example, the following
rule matches log messages sent by the ``example'' process which have log
priority levels in the range emergency to error. If a received message
matches, syslogd posts a BSD notification for the key
``com.example.log_message''.
? [= Sender example] [<= Level error] notify
com.example.log_message
Query Format
Queries comprise one or more message matching components, each of which
has the form:
[OP KEY VAL]
OP is a comparison operator. It can have the following values:
T true (always matches)
= equal
! not equal
> greater than
>= greater than or equal to
< less than
<= less than or equal to
It can also be preceded by one or more modifiers:
C casefold
N numeric comparison
S substring
A prefix
Z suffix
KEY and VAL are message keys and values. For example
[= Sender example]
matches any message with value ``example'' for the ``Sender'' key. The
query
[CA= Color gr]
matches any message with a value beginning with the letters GR, Gr, gr,
or gR ( ``C'' meaning casefold, ``A'' meaning prefix) for the ``Color''
key. The example query above,
[= Sender example] [N< Level 3]
matches any message from ``example'' with a level numerically less than 3
(string values are converted to integers, and the comparison is done on
the integer values). Note that the string values may be used equiva-
lently for the Level key, so the example above may also be written as:
[= Sender example] [< Level Error]
String values for levels may be any of the set ``emergency'', ``alert'',
``critical'', ``error'', ``warning'', ``notice'', ``info'', or ``debug''.
These strings may be upper, lower, or mixed case.
The ``T'' operator is useful to test for the presence of a particular
key.
[T Flavor]
Will match any message that has a ``Flavor'' key, regardless of its
value.
As a special case, the query
*
matches all messages.
Actions
The following actions are available.
store Causes syslogd to save matching messages in the ASL
database. Note that if /etc/asl.conf contains no
``store'' action rules, then syslogd will save all mes-
sages it receives in the ASL database.
file Causes matching messages to be stored in a log file.
The file's path name must follow as the first parameter.
If the path already exists, it must be a plain file. If
the file does not exist, it will be created when the
first message is written. If the pathname specified is
not an absolute path, syslogd will treat the given path
as relative to /var/log (for /etc/asl.conf), or for
other output modules relative to /var/log/module/NAME
where NAME is the module name.
By default, the file's owner will be root, and the file
will be readable by the admin group. Various options
may follow the file name to specify ownership and access
controls, printed log message format, and controls for
file rotation, compression, time-to-live, and other
aspects of output file life-cycle management. See the
OUTPUT CONFIGURATION SETTINGS section for more details.
directory Causes matching messages to be stored in an ASL-format
log message data store. A directory path name must fol-
low as the first parameter. If the path exists, it must
be a directory.
Messages saved to an ASL directory are saved in files
that are named ``yyyy.mm.dd.asl'', where ``yyyy'',
``mm'', and ``dd'' are the year, month (01 to 12) and
day of the month (01 to 31) associated with matching
messages. This has the effect of saving messages in a
separate file for each day.
By default, files in the directory will be owned by
root, and readable by the admin group. Various options
may follow the directory name to control ownership,
access controls, and the management of the store and its
contents. See the OUTPUT CONFIGURATION SETTINGS section
for a list of options that may be set for store directo-
ries.
notify Causes syslogd to post a notification with
notify_post(). The notification key must appear as a
single parameter following the ``notify'' action.
skip Causes a matching message to be ignored in all subse-
quent matching rules in the file. Its scope is local to
a single module configuration file.
claim Messages that match the query associated with a
``claim'' action are not processed by the main ASL con-
figuration file /etc/asl.conf. While claimed messages
are not processed by /etc/asl.conf, they are not com-
pletely private. Other modules may also claim messages,
and in some cases two or more modules may have claim
actions that match the same messages. This action only
blocks processing by /etc/asl.conf.
The ``claim'' action may be followed by the keyword
``only''. In this case, only those messages that match
the ``claim only'' query will be processed by subsequent
rules in the module.
access Sets read access controls for messages that match the
associated query pattern. syslogd will restrict read
access to matching messages to a specific user and
group. The user ID number and group ID number must fol-
low the ``access'' keyword as parameters.
broadcast Causes syslogd to write the text of matching messages to
all terminal windows. If optional text follows the
``broadcast'' keyword, then that text is written rather
that the matching message text. Note that this action
is restricted to the main ASL configuration file
/etc/asl.conf.
ignore Causes a matching message to be ignored in all subse-
quent matching rules in the file. This action is equiv-
alent to the ``skip'' action in all module configuration
files except the main ASL configuration file
/etc/asl.conf. When used in the main configuration
file, the scope of the action is global, and matching
messages will be ignored by all ASL modules.
OUTPUT CONFIGURATION SETTINGS
Various options may follow the path name in a ``file'' or ``directory''
query-action rule. For example, the following rule specifies that all
messages from the ``example'' facility will be saved in the file
``example.log'', and that messages are printed in a ``raw'' format that
shows all the keys and values in the message:
? [= Facility example] file example.log format=raw
Multiple options may be specified separated by whitespace characters.
For example:
? [= Facility example] file example.log format=raw rotate=local
compress ttl=3 mode=0640 uid=0 gid=5 gid=20
As a convenience, a file or directory name and any associated options can
be specified on a separate output configuration line following a ``>''
character:
> example.log format=raw rotate=local compress ttl=3 mode=0640
uid=0 gid=5 gid=20
Options for a file or directory are taken from the first query-action
rule or output configuration line for the given path. A good usage pat-
tern for multiple rules that specify the same output file or directory
is:
> example.log options ...
? query1 file example.log
? query2 file example.log
? query3 file example.log
Most of the options listed below may be used with either file or direc-
tory outputs. Exceptions are noted.
format=FMT Controls the format of log messages saved in a file.
Note that this option is specific to file outputs.
It is ignored for ASL directories.
The format is specified by the value given for FMT.
Several pre-defined formats are available:
bsd Format used by the syslogd daemon for system
log files, e.g. /var/log/system.log.
std Standard (default) format. Similar to ``bsd'',
but includes the message priority level.
raw Prints the complete message structure. Each
key/value pair is enclosed in square brackets.
Embedded closing brackets and white space are
escaped. Time stamps are printed as seconds
since the epoch.
xml The list of messages is printed as an XML prop-
erty list. Each message is represented as a
dictionary in a array. Dictionary keys repre-
sent message keys. Dictionary values are
strings.
asl The output file is written as an ASL-format
data store file. Files in this format may be
read and searched using the syslog command line
utility with the use of the -f path option.
Custom format strings may also be specified. Since
custom formats often contain white-space characters,
the entire string may be enclosed in single or double
quote characters, or each white-space character may
be preceded by a backslash escape character. Escaped
characters are not interpreted. Custom format
strings are described in detail in the READING MES-
SAGES section of the syslog(1) manual.
mode=MMM Sets the mode of the file or files within an ASL
directory. The value MMM may be specified as a deci-
mal value, a hexadecimal value (if preceded by
``0x''), or octal value (if preceded by ``0'').
uid=UUU Specifies the file's owner. If more than one
``uid=UUU'' option is given, the first will be used
to set ownership, and subsequent user IDs will be
given read access to in the files POSIX.1e ACLs.
Note that UIDs should be defined in the local Open
Directory database, since syslogd starts and may cre-
ate the log file before network directory services
are available. Unknown UIDs and GIDs will be ignored
when setting access controls.
gid=GGG Specifies the file's group. If more than one
``gid=GGG'' option is given, the first will be used
to set the file's group, and subsequent group IDs
will be given read access to in the files POSIX.1e
ACLs. As with UID=UUU options, groups should be
defined in the local Open Directory database.
coalesce=VAL By default, files printed using the ``bsd'' and
``std'' formats will coalesce duplicates. If two or
more messages are logged within 30 seconds, and which
differ only in time, then the second and subsequent
messages will not be printed. When a different mes-
sage is logged, or 30 seconds have elapsed since the
initial message was logged, a line with the text
--- last message repeated N times ---
will be added to the file. The default is
``coalesce=1''. The default may be overridden by
specifying ``coalesce=0''. The values ``off'' and
``false'' may be used in place of ``0''.
The following options all deal with file rotation and life-cycle manage-
ment. The FILE ROTATION section describes this in detail.
rotate=NAME_STYLE Enables log file rotation and specifies the file
naming scheme for rotated files. This option
does not apply to ASL directories. Four styles
are supported:
sec Rotated file names are of the form
``example.log.T1340607600''. The
file names include the creation
time of the file in seconds since
the epoch.
utc Rotated file names are in ISO 8601
extended format, for example
``example.log.2012-06-24T07:00:00Z''.
The file names includes its cre-
ation time as a UTC date and time.
utc-basic Rotated file names are in ISO 8601
basic format, for example
``example.log.20120624T070000Z''.
The file names includes its cre-
ation time as a UTC date and time.
local Rotated file names are in ISO 8601
extended format, for example
``example.log.2012-06-24T07:00:00-7''.
The file names includes its cre-
ation time as date and time in the
local time zone. The local time-
zone offset is included as a trail-
ing part of the name.
local-basic Rotated file names are in ISO 8601
basic format, for example
``example.log.20120624T070000-07''.
The file names includes its cre-
ation time as date and time in the
local time zone. The local time-
zone offset is included as a trail-
ing part of the name.
seq Rotated file names are of the form
``example.log.N'' where N is an
integer sequence number. Files are
re-numbered on each rotation so
that the ``0'' file is the most
recent.
If the option ``rotate'' appears without a
value, the naming style defaults to ``sec''.
Note that using the local timezone for times-
tamped files may cause odd behavior on highly-
mobile systems. aslmanager will delete files
after a specified time-to-live (see below). The
age of the file is determined by the file name.
If files are created in different timezones but
saved with a non-absolute timestamp, the age
calculation may result in some files being con-
sidered older or newer than they are in reality.
Also note that sequenced files (using the
``sec'' style) will initially be checkpointed
using a file name containing a timestamp in sec-
onds. aslmanager will re-sequence the files
when it scans for checkpoint files.
ttl=DAYS Specifies the number of days that older versions
of rotated files should be allowed to remain in
the filesystem. Rotated files older than this
limit are deleted.
dest=PATH By default, rotated files are left in the same
directory as the original file. However, in
some cases it may be useful to move the rotated
versions to a different directory for archival
or other reasons. If this option is specified,
aslmanager will move files to the directory
given by PATH.
soft Makes syslogd ignore write errors when saving
messages. Normally, syslogd will stop saving to
a file or ASL directory after 5 consecutive
write errors.
compress Enables gzip file compression for rotated log
files. When compressed, the extension ``.gz''
is appended to the file name.
file_max=SIZE Limits the size of an active log file. SIZE may
be an integer number of bytes, or the value may
be followed by a single character ``k'', ``m'',
or ``g'' (upper or lower case), to indicate a
size limit in multiples of 1024 (kibibyte),
1048576 (mebibyte), or 1073741824 (gibibyte).
If a file exceeds this limit, it is immediately
checkpointed by syslogd and a new file is
opened. Note that ``file_max'' specifies a size
limit before file compression is performed if
the ``compress'' option is also present.
all_max=SIZE Specifies a size limit for the total of all
rotated versions of a file. aslmanager will
delete rotated files, oldest first, to reduce
the total below the limit. SIZE may be speci-
fied in the same format as the file_max option.
FILE ROTATION
syslogd and aslmanager work together to automatically provide all the
features of file rotation. However, it is useful to understand how the
process works. This section describes the file rotation options that may
be used in /etc/asl.conf or an ASL Output Module configuration file,
together with a description of how the system works to support those fea-
tures.
If a file is marked for rotation, syslogd will close the file at the
start of a new day or when the file exceeds its ``file_max'' size limit.
At that point, syslogd renames the file and starts a new file to continue
logging. The old file is renamed with the file's creation time included
in its name. This operation is called checkpointing the file.
For example, syslogd might close ``example.log'' and rename it
``example.log.T1340521200'', 1340521200 being the time that the file was
created. It would then start a new ``example.log'' file and use it until
midnight, when the cycle would be repeated.
Files are normally checkpointed at midnight. If the system is sleeping
or powered off, then files are checkpointed when the the first message of
a new day (local time) is received. Files are also checkpointed if they
exceed a size limit specified by a file_max option, and they may be
checkpointed manually through options provided by the syslog(1) and
aslmanager(8) utilities. The checkpointed file name always contains the
file's creation time. If the options for the file include ``rotate=utc''
then the timestamp will be a UTC date and time string. ``rotate=local''
causes the timestamp to be the date and time in the current local time-
zone. Otherwise, the timestamp will be in seconds since the epoch.
syslogd only performs the checkpointing operation. It closes old files,
moves them out of the way, and starts writing new files. Most of the
work of file rotation is done by the aslmanager(8) utility. That
includes moving files to a destination directory, compressing files, re-
naming files according to one of the naming style options, deleting old
files after they exceed their time-to-live, and checking file space
usage.
aslmanager normally runs once during system start-up, and once a day just
after midnight. It may also be triggered occasionally by syslogd, and it
may be run manually.
aslmanager scans for any checkpointed files created by syslogd and will
rename the files (if required) to match the naming style specified by the
``rotate=NAME_STYLE'' option. If ``rotate=seq'' is specified for a file,
checkpointed files created by syslogd contain a timestamp in seconds.
These files are renamed so that the file names contain a sequence number.
The most recent version has the number ``0'', and older versions have
higher numbers. For example:
example.log.0
example.log.1
example.log.2
...
As well as renaming files, aslmanager may perform other actions. If the
file has been given a ``dest=PATH'' option, the rotated versions of the
file will be moved to the specified directory. Files will be gzip com-
pressed using the zlib(3) library if the ``compress'' option has been
given. If the total size of all the rotated versions of the file exceeds
a value given in an ``all_max'' option, older version of the rotated file
will be deleted to keep the total below the specified limit.
Although checkpoint and file rotation operations are normally done auto-
matically, aslmanager supports an option that will trigger syslogd to
checkpoint files before aslmanager starts its scan. syslog also supports
an option to force files to be checkpointed without running aslmanager.
See the aslmanager(8) and syslog(1) manuals for details.
ASL OUTPUT MODULES
An ASL output module is created by a configuration file in the directory
/etc/asl. The file name is used as the module's name. The format of the
file is generally the same as asl.conf with a few exceptions. Mdules may
not have parameter setting lines for the system parameters listed in the
PARAMETER SETTINGS or ASLMANAGER PARAMETER SETTINGS sections, nor may
they include ``broadcast'' query-action rules.
Module configuration files are read by syslogd when it starts, and when-
ever it gets a HUP signal. Messages received by syslogd are first pro-
cessed according the the rules found in /etc/asl.conf (also known as the
``com.apple.asl'' module), then the message is processed by the rules
from each module found in /etc/asl.
An exception to this is that messages that match the query in a ``claim''
action rule in any module are not processed by the rules in
/etc/asl.conf.
ASL output modules are enabled by default, but a module may include a
parameter setting:
= enable 0
The module is still loaded by syslogd, but the module will not save mes-
sages to files or directories, and will not post BSD notifications.
Several mechanisms allow modules to be enabled or disabled dynamically.
One mechanism allows the setting of the ``enable'' parameter to be based
on the existence of a path in the filesystem, or on the value associated
with a dictionary key in a property list file. On iOS only, the value of
a key in an installed configuration profile may be tested.
To enable a module based on the existence of a file, the module may use:
= enable [File /a/b/c]
where ``/a/b/c'' may be any filesystem path.
To enable a module based on the value of a dictionary key in a property
list file,
= enable [Plist /path/config.plist] [= SomeKey SomeValue]
Any of the test operations described above in the QUERY-ACTION RULES sec-
tion may also be used in testing key / value pairs. Multiple operations
are also allowed, for example:
= enable [Plist /path/config.plist] [N>= DebugLevel 7] [S=
Othervalue xyz]
If the property list file does not exist, the test will evaluate to zero.
The file may be in binary or xml format. It may only contain a single
dictionary object at its top level. Only keys and values at the top
level of the dictionary may be tested. Values must be strings, integer
values, doubles, UUIDs, dates, or booleans. Boolean <true/> and <false/>
values are converted to 1 and 0 respectively. Values are converted into
strings, and string comparisons are used unless unless an ``N'' modifier
is specified with the test operator.
On iOS, a module may test key / value pairs in a configuration profile
using the same key / value tests that may be used for property list
files.
= enable [Profile name] [= Verbose 1]
The profile name is the value of its DefaultsDomainName key. The test
will evaluate to zero if the profile is not installed.
A module may be also enabled or disabled using syslog or by sending
syslogd a special asl(3) control message. Only the user ``root'' may
enable or disable modules.
A module may be enabled or disabled by sending an asl(3) message as shown
in this example, which enables a module named ``com.apple.example'':
#include <asl.h>
aslmsg ctl = asl_new(ASL_TYPE_MSG);
asl_set(ctl, ASL_KEY_OPTION, "control");
asl_set(ctl, ASL_KEY_MSG, "@ com.apple.example enable 1");
asl_send(NULL, ctl);
asl_free(ctl);
A control message may also be sent using syslog as the following example
shows to disable a module named ``com.apple.example'':
sudo syslog -module com.apple.example enable 0
A module may also enable or disable itself. Although a module that is
not enabled will not write or post notifications, it still will scan mes-
sages. The module may contain conditional parameter-setting rules like:
= [= Color Green] enable 1
= [= Color Red] enable 0
This is similar to a query-action rule. If a message received by syslogd
matches the specified query, in this case having a Color key with the
value Green or Red, then the enable parameter is set as specified. So in
this example, the module would be enabled and disabled whenever syslogd
received a message containing the appropriate value for the ``Color''
key.
ASLMANAGER PARAMETER SETTINGS
The following parameter-settings are recognized by aslmanager.
aslmanager_debug Enables or disables internal debugging output.
This is probably of little interest to most
users. The debug parameter requires a value of
``1'' to enable debug output, or a value of ``0''
to disable it. Debug messages saved in an auxil-
iary file attached to an ASL log message. The
file may be inspected by opening the file
attachement from the Console utility.
store_ttl Sets the time-to-live in days for messages in the
ASL database. The default is 7 days.
max_store_size Sets the maximum size for for the ASL database.
The default is 150000000 bytes.
archive Enables or disables archiving of the ASL data-
base. The archive parameter requires a value of
``1'' to enable archiving, or a value of ``0'' to
disable it. An option archive directory path may
follow the ``0'' or ``1''. If enabled, files
removed from the ASL database are moved to the
archive directory. The default archive directory
path is /var/log/asl.archive.
store_path The ASL database path used by aslmanager. The
default is /var/log/asl. Note that this parame-
ter is ignored by syslogd.
archive_mode Files copied to the ASL database archive will be
given the specified access mode. The default is
0400, so archive files will only be readable by
root.
SEE ALSO
asl(3), notify(3), syslog(1), aslmanager(8), syslogd(8).
Mac OS X Sept 19, 2008 Mac OS X
Mac OS X 10.9 - Generated Wed Oct 16 18:16:59 CDT 2013