MongoDB Documentation  Release 3.0.4 Collection on all mongod Instances On startup  each mongod instance inserts a document into startup_log (page 653) with diagnostic informa- tion about the mongod instance itself and host information. startup_log (page 653) is a capped collection. This information is primarily useful for diagnostic purposes. Example Consider the following prototype of a document from the startup_log (page 653) collection: Documents in the startup_log (page 653) collection contain the following fields: Includes the system hostname and a millisecond epoch value. The system’s hostname. A UTC ISODate value that reflects when the server started. A string that reports the startTime (page 653) in the system’s local time zone. An embedded document that reports the mongod runtime options and their values. The process identifier for this process. An embedded document that reports information about the build environment and settings used to compile this mongod . This is the same output as buildInfo . See buildInfo . 9.4. Replication Reference 653 local.startup_log. buildinfo local.startup_log. pid local.startup_log. cmdLine local.startup_log. startTimeLocal local.startup_log. startTime local.startup_log. hostname local.startup_log. _id { "_id" : "<string>"  "hostname" : "<string>"  "startTime" : ISODate("<date>")  "startTimeLocal" : "<string>"  "cmdLine" : { "dbpath" : "<path>"  "<option>" : <value> }  "pid" : <number>  "buildinfo" : { "version" : "<string>"  "gitVersion" : "<string>"  "sysInfo" : "<string>"  "loaderFlags" : "<string>"  "compilerFlags" : "<string>"  "allocator" : "<string>"  "versionArray" : [ <num>  <num>  <...> ]  "javascriptEngine" : "<string>"  "bits" : <number>  "debug" : < boolean >  "maxBsonObjectSize" : <number> } } local. startup_log