Audit Daemon's Role

The following list summarizes what the audit daemon, auditd, does.

• auditd opens and closes audit log files in the directories specified in the audit_control file, in the order in which they are specified.

• auditd reads audit data from the kernel and writes it to an audit file.

• auditd executes the audit_warn script when the audit directories fill past limits specified in the audit_control file. The script, by default, sends warnings to the audit_warn alias and to the console.

• With the system default configuration, when all audit directories are full, processes that generate audit records are suspended. In addition, auditd writes a message to the console and to the audit_warn alias. (The auditing policy can be reconfigured with autoconfig.) At this point only the system administrator can log in to write audit files to tape, delete audit files from the system, or do other cleanup.

When the audit daemon starts as the machine is brought up to multiuser mode, or when the audit daemon is instructed by the audit -s command to reread the file after the file has been edited, auditd determines the amount of free space necessary and reads the list of directories from the audit_control file. It then uses those directories as possible locations for creating audit files.

The audit daemon maintains a pointer into this list of directories, starting with the first. Every time the audit daemon needs to create an audit file, it puts the file into the first available directory in the list, starting at the audit daemon's current pointer. The pointer can be reset to the beginning of the list if the administrator enters the audit -s command. When you use the audit -n command to instruct the daemon to switch to a new audit file, the new file is created in the same directory as the current file.