Provided by: auditd_3.1.2-2.1build1.1_amd64 
NAME
auditd.conf - audit daemon configuration file
DESCRIPTION
The file /etc/audit/auditd.conf contains configuration information specific to the audit daemon. Each
line should contain one configuration keyword, an equal sign, and then followed by appropriate
configuration information. All option names and values are case insensitive. The keywords recognized are
listed and described below. Each line should be limited to 160 characters or the line will be skipped.
You may add comments to the file by starting the line with a '#' character.
local_events
This yes/no keyword specifies whether or not to include local events. Normally you want local
events so the default value is yes. Cases where you would set this to no is when you want to
aggregate events only from the network. At the moment, this is useful if the audit daemon is
running in a container. This option can only be set once at daemon start up. Reloading the config
file has no effect.
log_file
This keyword specifies the full path name to the log file where audit records will be stored. It
must be a regular file.
write_logs
This yes/no keyword determines whether or not to write logs to the disk. Normally you want this
so the default is yes.
log_format
The log format describes how the information should be stored on disk. There are 2 options: raw
and enriched. If set to RAW, the audit records will be stored in a format exactly as the kernel
sends it. The ENRICHED option will resolve all uid, gid, syscall, architecture, and socket address
information before writing the event to disk. This aids in making sense of events created on one
system but reported/analyzed on another system. The NOLOG option is now deprecated. If you were
setting this format, now you should set the write_logs option to no.
log_group
This keyword specifies the group that is applied to the log file's permissions. The default is
root. The group name can be either numeric or spelled out.
priority_boost
This is a non-negative number that tells the audit daemon how much of a priority boost it should
take. The default is 4. No change is 0.
flush Valid values are none, incremental, incremental_async, data, and sync. If set to none, no
special effort is made to flush the audit records to disk. If set to incremental, Then the freq
parameter is used to determine how often an explicit flush to disk is issued. The
incremental_async parameter is very much like incremental except the flushing is done
asynchronously for higher performance. The data parameter tells the audit daemon to keep the data
portion of the disk file sync'd at all times. The sync option tells the audit daemon to keep both
the data and meta-data fully sync'd with every write to disk. The default value is
incremental_async.
freq This is a non-negative number that tells the audit daemon how many records to write before issuing
an explicit flush to disk command. This value is only valid when the flush keyword is set to
incremental or incremental_async.
num_logs
This keyword specifies the number of log files to keep if rotate is given as the
max_log_file_action. If the number is < 2, logs are not rotated. This number must be 999 or less.
The default is 0 - which means no rotation. As you increase the number of log files being rotated,
you may need to adjust the kernel backlog setting upwards since it takes more time to rotate the
files. This is typically done in /etc/audit/audit.rules. If log rotation is configured to occur,
the daemon will check for excess logs and remove them in effort to keep disk space available. The
excess log check is only done on startup and when a reconfigure results in a space check.
name_format
This option controls how computer node names are inserted into the audit event stream. It has the
following choices: none, hostname, fqd, numeric, and user. None means that no computer name is
inserted into the audit event. hostname is the name returned by the gethostname syscall. The fqd
means that it takes the hostname and resolves it with dns for a fully qualified domain name of
that machine. Numeric is similar to fqd except it resolves the IP address of the machine. In
order to use this option, you might want to test that 'hostname -i' or 'domainname -i' returns a
numeric address. Also, this option is not recommended if dhcp is used because you could have
different addresses over time for the same machine. User is an admin defined string from the name
option. The default value is none.
name This is the admin defined string that identifies the machine if user is given as the name_format
option.
max_log_file
This keyword specifies the maximum file size in megabytes. When this limit is reached, it will
trigger a configurable action. The value given must be numeric.
max_log_file_action
This parameter tells the system what action to take when the system has detected that the max file
size limit has been reached. Valid values are ignore, syslog, suspend, rotate and keep_logs. If
set to ignore, the audit daemon does nothing. syslog means that it will issue a warning to
syslog. suspend will cause the audit daemon to stop writing records to the disk. The daemon will
still be alive. The rotate option will cause the audit daemon to rotate the logs. It should be
noted that logs with higher numbers are older than logs with lower numbers. This is the same
convention used by the logrotate utility. The keep_logs option is similar to rotate except it does
not use the num_logs setting. This prevents audit logs from being overwritten. The effect is that
logs accumulate and are not deleted - which will trigger the space_left_action if the volume fills
up. This is best used in combination with an external script used to archive logs on a periodic
basis.
verify_email
This option determines if the email address given in action_mail_acct is checked to see if the
domain name can be resolved. This option must be given before action_mail_acct or the default
value of yes will be used.
action_mail_acct
This option should contain a valid email address or alias. The default address is root. If the
email address is not local to the machine, you must make sure you have email properly configured
on your machine and network. Also, this option requires that /usr/lib/sendmail exists on the
machine.
space_left
If the free space in the filesystem containing log_file drops below this value, the audit daemon
takes the action specified by space_left_action. If the value of space_left is specified as a
whole number, it is interpreted as an absolute size in megabytes (MiB). If the value is specified
as a number between 1 and 99 followed by a percentage sign (e.g., 5%), the audit daemon calculates
the absolute size in megabytes based on the size of the filesystem containing log_file. (E.g., if
the filesystem containing log_file is 2 gigabytes in size, and space_left is set to 25%, then the
audit daemon sets space_left to approximately 500 megabytes. Note that this calculation is
performed when the audit daemon starts, so if you resize the filesystem containing log_file while
the audit daemon is running, you should send the audit daemon SIGHUP to re-read the configuration
file and recalculate the correct percentage.
space_left_action
This parameter tells the system what action to take when the system has detected that it is
starting to get low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend,
single, and halt. If set to ignore, the audit daemon does nothing. syslog means that it will
issue a warning to syslog. rotate will rotate logs, losing the oldest to free up space. Email
means that it will send a warning to the email account specified in action_mail_acct as well as
sending the message to syslog. exec /path-to-script will execute the script. You cannot pass
parameters to the script. The script is also responsible for telling the auditd daemon to resume
logging once its completed its action. This can be done by adding service auditd resume to the
script. suspend will cause the audit daemon to stop writing records to the disk. The daemon will
still be alive. The single option will cause the audit daemon to put the computer system in single
user mode. The halt option will cause the audit daemon to shutdown the computer system. Except for
rotate, it will perform this action just one time.
admin_space_left
This is a numeric value in megabytes that tells the audit daemon when to perform a configurable
action because the system is running low on disk space. This should be considered the last chance
to do something before running out of disk space. The numeric value for this parameter should be
lower than the number for space_left. You may also append a percent sign (e.g. 1%) to the number
to have the audit daemon calculate the number based on the disk partition size.
admin_space_left_action
This parameter tells the system what action to take when the system has detected that it is low on
disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt. If
set to ignore, the audit daemon does nothing. Syslog means that it will issue a warning to
syslog. rotate will rotate logs, losing the oldest to free up space. Email means that it will
send a warning to the email account specified in action_mail_acct as well as sending the message
to syslog. exec /path-to-script will execute the script. You cannot pass parameters to the
script. The script is also responsible for telling the auditd daemon to resume logging once its
completed its action. This can be done by adding service auditd resume to the script. Suspend
will cause the audit daemon to stop writing records to the disk. The daemon will still be alive.
The single option will cause the audit daemon to put the computer system in single user mode. The
halt option will cause the audit daemon to shutdown the computer system. Except for rotate, it
will perform this action just one time.
disk_full_action
This parameter tells the system what action to take when the system has detected that the
partition to which log files are written has become full. Valid values are ignore, syslog, rotate,
exec, suspend, single, and halt. If set to ignore, the audit daemon will issue a syslog message
but no other action is taken. Syslog means that it will issue a warning to syslog. rotate will
rotate logs, losing the oldest to free up space. exec /path-to-script will execute the script.
You cannot pass parameters to the script. The script is also responsible for telling the auditd
daemon to resume logging g once its completed its action. This can be done by adding service
auditd resume to the script. Suspend will cause the audit daemon to stop writing records to the
disk. The daemon will still be alive. The single option will cause the audit daemon to put the
computer system in single user mode. halt option will cause the audit daemon to shutdown the
computer system.
disk_error_action
This parameter tells the system what action to take whenever there is an error detected when
writing audit events to disk or rotating logs. Valid values are ignore, syslog, exec, suspend,
single, and halt. If set to ignore, the audit daemon will not take any action. Syslog means that
it will issue no more than 5 consecutive warnings to syslog. exec /path-to-script will execute
the script. You cannot pass parameters to the script. Suspend will cause the audit daemon to stop
writing records to the disk. The daemon will still be alive. The single option will cause the
audit daemon to put the computer system in single user mode. halt option will cause the audit
daemon to shutdown the computer system.
tcp_listen_port
This is a numeric value in the range 1..65535 which, if specified, causes auditd to listen on the
corresponding TCP port for audit records from remote systems. The audit daemon may be linked with
tcp_wrappers. You may want to control access with an entry in the hosts.allow and deny files. If
this is deployed on a systemd based OS, then you may need to adjust the 'After' directive. See the
note in the auditd.service file.
tcp_listen_queue
This is a numeric value which indicates how many pending (requested but unaccepted) connections
are allowed. The default is 5. Setting this too small may cause connections to be rejected if
too many hosts start up at exactly the same time, such as after a power failure. This setting is
only used for aggregating servers. Clients logging to a remote server should keep this commented
out.
tcp_max_per_addr
This is a numeric value which indicates how many concurrent connections from one IP address is
allowed. The default is 1 and the maximum is 1024. Setting this too large may allow for a Denial
of Service attack on the logging server. Also note that the kernel has an internal maximum that
will eventually prevent this even if auditd allows it by config. The default should be adequate in
most cases unless a custom written recovery script runs to forward unsent events. In this case you
would increase the number only large enough to let it in too.
use_libwrap
This setting determines whether or not to use tcp_wrappers to discern connection attempts that are
from allowed machines. Legal values are either yes, or no The default value is yes.
tcp_client_ports
This parameter may be a single numeric value or two values separated by a dash (no spaces
allowed). It indicates which client ports are allowed for incoming connections. If not
specified, any port is allowed. Allowed values are 1..65535. For example, to require the client
use a privileged port, specify 1-1023 for this parameter. You will also need to set the local_port
option in the audisp-remote.conf file. Making sure that clients send from a privileged port is a
security feature to prevent log injection attacks by untrusted users.
tcp_client_max_idle
This parameter indicates the number of seconds that a client may be idle (i.e. no data from them
at all) before auditd complains. This is used to close inactive connections if the client machine
has a problem where it cannot shutdown the connection cleanly. Note that this is a global setting,
and must be higher than any individual client heartbeat_timeout setting, preferably by a factor of
two. The default is zero, which disables this check.
transport
If set to TCP, only clear text tcp connections will be used. If set to KRB5, then Kerberos 5 will
be used for authentication and encryption. The default value is TCP.
enable_krb5
This option is deprecated. Use the transport option above instead. If set to "yes", Kerberos 5
will be used for authentication and encryption. The default is "no". If this option is set to
"yes" and it follows the transport option, it will override the transport setting. This would be
the normal expected behavior for backwards compatibility.
krb5_principal
This is the principal for this server. The default is "auditd". Given this default, the server
will look for a key named like auditd/hostname@EXAMPLE.COM stored in /etc/audit/audit.key to
authenticate itself, where hostname is the canonical name for the server's host, as returned by a
DNS lookup of its IP address.
krb5_key_file
Location of the key for this client's principal. Note that the key file must be owned by root and
mode 0400. The default is /etc/audit/audit.key
distribute_network
If set to "yes", network originating events will be distributed to the audit dispatcher for
processing. The default is "no".
q_depth
This is a numeric value that tells how big to make the internal queue of the audit event
dispatcher. A bigger queue lets it handle a flood of events better, but could hold events that are
not processed when the daemon is terminated. If you get messages in syslog about events getting
dropped, increase this value. The default value is 2000.
overflow_action
This option determines how the daemon should react to overflowing its internal queue. When this
happens, it means that more events are being received than it can pass along to child processes.
This error means that it is going to lose the current event that it's trying to dispatch. This
option has the following choices: ignore, syslog, suspend, single, and halt. If set to ignore,
the audit daemon does nothing. syslog means that it will issue a warning to syslog. suspend will
cause the audit daemon to stop sending events to child processes. The daemon will still be alive.
The single option will cause the audit daemon to put the computer system in single user mode.
halt option will cause the audit daemon to shutdown the computer system.
max_restarts
This is a non-negative number that tells the audit event dispatcher how many times it can try to
restart a crashed plugin. The default is 10.
plugin_dir
This is the location that auditd will use to search for its plugin configuration files.
end_of_event_timeout
This is a non-negative number of seconds used by the userspace auparse() library routines and the
aureport(8) , ausearch(8) utilities to consider an event is complete when parsing an event log
stream. For an event stream being processed, if the time of the current event is over
end_of_event_timeout seconds old, compared to co-located events, then the event is considered
complete. See the NOTES section for more detail.
NOTES
In a CAPP environment, the audit trail is considered so important that access to system resources must be
denied if an audit trail cannot be created. In this environment, it would be suggested that
/var/log/audit be on its own partition. This is to ensure that space detection is accurate and that no
other process comes along and consumes part of it.
The flush parameter should be set to sync or data.
Max_log_file and num_logs need to be adjusted so that you get complete use of your partition. It should
be noted that the more files that have to be rotated, the longer it takes to get back to receiving audit
events. Max_log_file_action should be set to keep_logs.
Space_left should be set to a number that gives the admin enough time to react to any alert message and
perform some maintenance to free up disk space. This would typically involve running the aureport -t
report and moving the oldest logs to an archive area. The value of space_left is site dependent since the
rate at which events are generated varies with each deployment. The space_left_action is recommended to
be set to email. If you need something like an snmp trap, you can use the exec option to send one.
Admin_space_left should be set to the amount of disk space on the audit partition needed for admin
actions to be recorded. Admin_space_left_action would be set to single so that use of the machine is
restricted to just the console.
The disk_full_action is triggered when no more room exists on the partition. All access should be
terminated since no more audit capability exists. This can be set to either single or halt.
The disk_error_action should be set to syslog, single, or halt depending on your local policies regarding
handling of hardware malfunctions.
Specifying a single allowed client port may make it difficult for the client to restart their audit
subsystem, as it will be unable to recreate a connection with the same host addresses and ports until the
connection closure TIME_WAIT state times out.
Auditd events are made up of one or more records. The auditd system cannot guarantee that the set of
records that make up an event will occur atomically, that is the stream will have interleaved records of
different events, IE
event0_record0
event1_record0
event2_record0
event1_record3
event2_record1
event1_record4
event3_record0
The auditd system does not guarantee that the records that make up an event will appear in order. Thus,
when processing event streams, we need to maintain a list of events with their own list of records hence
List of List (LOL) event processing.
When processing an event stream we define the end of an event via
record type = AUDIT_EOE (audit end of event type record), or
record type = AUDIT_PROCTITLE (we note the AUDIT_PROCTITLE is always the last record), or
record type = AUDIT_KERNEL (kernel events are one record events), or
record type < AUDIT_FIRST_EVENT (only single record events appear before this type), or
record type >= AUDIT_FIRST_ANOM_MSG (only single record events appear after this type), or
record type >= AUDIT_MAC_UNLBL_ALLOW && record type <= AUDIT_MAC_CALIPSO_DEL (these are also one
record events), or
for the stream being processed, the time of the event is over end_of_event_timeout seconds old.
FILES
/etc/audit/auditd.conf
Audit daemon configuration file
SEE ALSO
auditd(8), audisp-remote.conf(5), auditd-plugins(5).
AUTHOR
Steve Grubb