7.3. Configuring the audit Service
7.3. Configuring the audit Service The Audit daemon can be configured in the /etc/audit/auditd.conf file. This file consists of configuration parameters that modify the behavior of the Audit daemon. Empty lines and text following a hash sign ( # ) are ignored. For further details, see the auditd.conf (5) man page. 7.3.1. Configuring auditd for a Secure Environment The default auditd configuration should be suitable for most environments. However, if your environment must meet strict security policies, the following settings are suggested for the Audit daemon configuration in the /etc/audit/auditd.conf file: log_file The directory that holds the Audit log files (usually /var/log/audit/ ) should reside on a separate mount point. This prevents other processes from consuming space in this directory and provides accurate detection of the remaining space for the Audit daemon. max_log_file Specifies the maximum size of a single Audit log file, which must be set to make full use of the available space on the partition that holds the Audit log files. The max_log_file parameter specifies the maximum file size in megabytes. The value given must be numeric. max_log_file_action Decides what action is taken once the limit set in max_log_file is reached, should be set to keep_logs to prevent Audit log files from being overwritten. space_left Specifies the amount of free space left on the disk for which an action that is set in the space_left_action parameter is triggered. Must be set to a number that gives the administrator enough time to respond and free up disk space. The space_left value depends on the rate at which the Audit log files are generated. 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 (for example, 5%), the audit daemon calculates the absolute size in megabytes based on the size of the file system containing log_file . space_left_action It is recommended to set the space_left_action parameter to email or exec with an appropriate notification method. admin_space_left Specifies the absolute minimum amount of free space for which an action that is set in the admin_space_left_action parameter is triggered, which must be set to a value that leaves enough space to log actions performed by the administrator. The numeric value for this parameter should be lower than the number for space_left . You can also append a percent sign (for example, 1%) to the number to have the audit daemon calculate the number based on the disk partition size. admin_space_left_action Should be set to single to put the system into single-user mode and allow the administrator to free up some disk space. disk_full_action Specifies an action that is triggered when no free space is available on the partition that holds the Audit log files, must be set to halt or single . This ensures that the system is either shut down or operating in single-user mode when Audit can no longer log events. disk_error_action Specifies an action that is triggered in case an error is detected on the partition that holds the Audit log files, must be set to syslog , single , or halt , depending on your local security policies regarding the handling of hardware malfunctions. flush Should be set to incremental_async . It works in combination with the freq parameter, which determines how many records can be sent to the disk before forcing a hard synchronization with the hard drive. The freq parameter should be set to 100 . These parameters assure that Audit event data is synchronized with the log files on the disk while keeping good performance for bursts of activity. The remaining configuration options should be set according to your local security policy.