NAME

logd — unified logging system daemon

DESCRIPTION

logd is the part of the unified logging system that is responsible for handling and managing historical data and related metadata. For example, it handles entries generated via the os_log(3) family of facilities.

{ process }
     `--- os_log ---> [ page ]
                      [ page ]
                      [ page ]
                          `---> { logd }
                                   | `---> [ buffer ]
                                   |
                                   `---> [ data store ]

All processes that use os_log(3) share pages of memory with logd and append entries to them. logd reads pages and combines and compresses this data. Depending on configured policies, it keeps them in a local ring buffer or writes them out to persistent storage.

{ logd }
   | `---> [ buffer ] ----.
   |                      ,`---> { log show }
   `---> [ data store ] -'

The log(1) utility can view these data by requesting logd for access to both the ring buffer and the persistent storage.

SEE ALSO

log(1), os_log(3), diagnosticd(8)

Logging | Apple Developer Documentation