syslog: log levels

Code	Severity	Description	General Description
0	Emergency	System is unusable.	A "panic" condition usually affecting multiple apps/servers/sites. At this level it would usually notify all tech staff on call.
1	Alert	Action must be taken immediately.	Should be corrected immediately, therefore notify staff who can fix the problem. An example would be the loss of a backup ISP connection.
2	Critical	Critical conditions.	Should be corrected immediately, but indicates failure in a primary system, an example is a loss of primary ISP connection.
3	Error	Error conditions.	Non-urgent failures, these should be relayed to developers or admins; each item must be resolved within a given time.
4	Warning	Warning conditions.	Warning messages, not an error, but indication that an error will occur if action is not taken, e.g. file system 85% full - each item must be resolved within a given time.
5	Notice	Normal but significant condition.	Events that are unusual but not error conditions - might be summarized in an email to developers or admins to spot potential problems - no immediate action required.
6	Informational	Informational messages.	Normal operational messages - may be harvested for reporting, measuring throughput, etc. - no action required.
7	Debug	Debug-level messages.	Info useful to developers for debugging the application, not useful during operations.

SEE ALSO:

• iptables: add chains
• iptables: logging
• syslog: log levels
• Enable iptables logging on Ubuntu Linux
• iptables: add new chains to log drop/accept messages