Basic Cluster Administration

mongod is the core database process. mongo is the interactive MongoDB shell that you use to connect to mongod.

mongod --dbpath /data/db --logpath /data/log/mongod.log --fork --replSet "M103" --keyFile /data/keyfile --bind_ip "127.0.0.1,192.168.103.100" --tlsMode requireTLS --tlsCAFile "/etc/tls/TLSCA.pem" --tlsCertificateKeyFile "/etc/tls/tls.pem"

note : --bind_ip 127.0.0.1,192.168.103.100

storage:
  dbPath: /data/db/
  journal:
    enabled: true
#  engine:
#  mmapv1:
#  wiredTiger:

# where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: first_mongod/mongod.log

# network interfaces
net:
  port: 27000
  bindIp: "127.0.0.1,192.168.103.100"


# how the process runs
processManagement:
   fork: true
   timeZoneInfo: /usr/share/zoneinfo
tls:
  mode: "requireTLS"
  certificateKeyFile: "/etc/tls/tls.pem"
  CAFile: "/etc/tls/TLSCA.pem"
security:
  keyFile: "/data/keyfile"
processManagement:
  fork: true
security:
  authorization: enabled

mongo admin --host localhost:27000 --eval '
  db.createUser({
    user: "m103-admin",
    pwd: "m103-pass",
    roles: [
      {role: "root", db: "admin"}
    ]
  })
'

db.createUser(
  { user: "m103-application-user",
    pwd: "m103-application-pass",
    roles: [ { db: "applicationData", role: "readWrite" } ]
  }
)

mongod --config /etc/mongod.conf

1. ERROR: child process failed, exited with error number 1 To see additional information in this output, start without the "--fork" option

vagrant@m103:~$ sudo nano /etc/mongod.conf
vagrant@m103:~$ mongod --config /etc/mongod.conf

2020-03-09T12:28:25.617 0000 F CONTROL [main] Failed global initialization: FileNotOpen: Failed to open "/first_mongod/mongod.log"

Solution: Make sure the folder is created, else create it using mkdir and assign RW access

sudo chown vagrant:vagrant first_mongod/mongod.log

2020-03-09T12:40:31.616 0000 E QUERY [thread1] Error: listDatabases failed:{ "ok" : 0, "errmsg" : "there are no users authenticated", "code" : 13, "codeName" : "Unauthorized" } : _getErrorWithCode@src/mongo/shell/utils.js:25:13 Mongo.prototype.getDBs@src/mongo/shell/mongo.js:67:1 shellHelper.show@src/mongo/shell/utils.js:860:19 shellHelper@src/mongo/shell/utils.js:750:15 @(shellhelp2):1:1 MongoDB Enterprise > db.auth('m103-admin','m103-pass') Error: Authentication failed.

Solution: Login with user credentials

mongo --host localhost:27000  --authenticationDatabase "admin" -u "m103-admin" -p "m103-pass"

3. QUERY [thread1] Error: listDatabases failed:{ "ok" : 0, "errmsg" : "not master and slaveOk=false", "code" : 13435, "codeName" : "NotMasterNoSlaveOk" } : _getErrorWithCode@src/mongo/shell/utils.js:25:13 Mongo.prototype.getDBs@src/mongo/shell/mongo.js:67:1 shellHelper.show@src/mongo/shell/utils.js:860:19 shellHelper@src/mongo/shell/utils.js:750:15 @(shellhelp2):1:1

Solution: Note: rs is the replication set

MongoDB Enterprise >

rs.status() 
{
	"info" : "run rs.initiate(...) if not yet done for the set",
	"ok" : 0,
	"errmsg" : "no replset config has been received",
	"code" : 94,
	"codeName" : "NotYetInitialized"
}

MongoDB Enterprise >

rs.initiate() 
{
	"info2" : "no configuration specified. Using a default configuration for the set",
	"me" : "192.168.103.100:27000",
	"ok" : 1
}

MongoDB Enterprise M103:OTHER>

rs.status()
{
	"set" : "M103",
	"date" : ISODate("2020-03-09T12:49:58.116Z"),
	"myState" : 1,
	"term" : NumberLong(1),
	"syncingTo" : "",
	"syncSourceHost" : "",
	"syncSourceId" : -1,
	"heartbeatIntervalMillis" : NumberLong(2000),
 ( Not complete)

4. Different DB path than the default path /data/db. Mongod will now store data files in this new directory instead. Solution: create a new folder /var/mongodb/db/ and allow mongod to write files to this directory create this directory with sudo, because /var is owned by root use chown to change the owner of this directory to vagrant:vagrant edit your config file to use this new directory as the dbpath

use admin
db.shutdownServer()
quit()

Start to see reflected changes

~$ mongod --config /etc/mongod.conf
Aborted (core dumped)

Solution: Likely there is an other instance of mongod running. Find the process and kill it

To find process

vagrant@m103:~$ sudo lsof -i -P -n | grep 27000 
mongod    2109 vagrant   12u  IPv4  13601      0t0  TCP 127.0.0.1:27000 (LISTEN)
mongod    2109 vagrant   13u  IPv4  13602      0t0  TCP 192.168.103.100:27000 (LISTEN)
mongo     2138 vagrant    4u  IPv4  13619      0t0  TCP 127.0.0.1:56336->127.0.0.1:27000 (ESTABLISHED)


vagrant@m103:~$ sudo lsof -i -P -n | grep mongod
mongod    2109 vagrant   12u  IPv4  13601      0t0  TCP 127.0.0.1:27000 (LISTEN)
mongod    2109 vagrant   13u  IPv4  13602      0t0  TCP 192.168.103.100:27000 (LISTEN)

To kill the process kill -9 2109

6. Detected unclean shutdown - /data/db/mongod.lock is not empty.

Solution:

mongod --repair

Not recommanded but if you want to repair your data files without preserving the original files

sudo rm /var/lib/mongodb/mongod.lock
sudo mongod --dbpath /var/lib/mongodb/ --repair
sudo mongod --dbpath /var/lib/mongodb/ --journal

Make sure that you leave you terminal running in which you have run above lines, don't press 'Ctrl c' or quit it. Type the command to start mongo now in another window.

7. Error: couldn't connect to server localhost:27000, connection attempt failed: SocketException: Error connecting to localhost:27000 (127.0.0.1:27000) :: caused by :: Connection refused : connect@src/mongo/shell/mongo.js:343:13 @(connect):2:6 exception: connect failed

Hint: Check the mongod logs for failure

8. exception in initAndListen: 29 Data directory /data/db not found., terminating Solution: Error happen because dbpath /data/db/ (default config) does not exist. You need to create data folder and set permission for it.

sudo mkdir -p /data/db/ 
sudo chown id -u /data/db

then start the mongo