mongo.config.yaml

storage:
    dbPath: "/data/db"
    journal:
        enabled: true
systemLog:
    destination: file
    path: "/var/log/mongodb.log"
    logAppend: true
    timeStampFormat: iso8601-utc
processManagement:
    fork: true
net:
    bindIp: 192.0.2.3
    port: 27019
security:
    keyFile: "/data/key/config.key"
    authorization: "enabled"
sharding:
    clusterRole: "configsvr"

mongod.conf.yaml

# http://dba.stackexchange.com/questions/82591/sample-yaml-configuration-files-for-mongodb
storage:
    engine: wiredTiger
    dbPath: "/var/lib/mongodb"
    directoryPerDB: true
    journal:
        enabled: true
systemLog:
    destination: file
    path: "/var/log/mongodb/mongod.log"
    logAppend: true
    timeStampFormat: iso8601-utc
processManagement:
    fork: true
net:
    bindIp: 127.0.0.1
    port: 27017
    wireObjectCheck : false
    unixDomainSocket: 
        enabled : true

mongod.repl.yaml

storage:
    dbPath: "/data/db"
    engine: "wiredTiger"
    wiredTiger:
        engineConfig: 
            cacheSizeGB: 8
        collectionConfig: 
            blockCompressor: snappy        
systemLog:
    destination: file
    path: "/var/log/mongodb.log"
    logAppend: true
    timeStampFormat: iso8601-utc
replication:
    oplogSizeMB: 10240
    replSetName: "rs1"
processManagement:
    fork: true
net:
    bindIp: "192.0.2.1,127.0.0.1"
    port: 27018
security:
    keyFile: "/data/key/rs1.key"
    authorization: "enabled"
sharding:
    clusterRole: "shardsvr"

mongod.shard.yaml

storage:
    dbPath: "/data/db"
    directoryPerDB: true
    journal:
        enabled: true
systemLog:
    destination: file
    path: "/var/log/mongodb.log"
    logAppend: true
    timeStampFormat: iso8601-utc
replication:
    oplogSizeMB: 10240
    replSetName: "rs1"
processManagement:
    fork: true
net:
    bindIp: 192.0.2.1
    port: 27018
security:
    keyFile: "/data/key/rs1.key"
    authorization: "enabled"
sharding:
    clusterRole: "shardsvr"

mongos.yaml

sharding:
    configDB: "config1.example.net:27019,config2.example.net:27019,config3.example.net:27019"
    autoSplit: true
systemLog:
    destination: file
    path: "/var/log/mongos.log"
processManagement:
    fork: true
net:
    port: 27017
    bindIp: 192.0.2.2
    maxIncomingConnections: 5000
security:
    keyFile: "/data/key/mongos.key"
    authorization: "enabled"