Just finished installing mongodb, however, I have not been able to make complete sense of the difference between mongo vs mongod commands. Yes, I do understand that
mongod is the primary daemon process for the MongoDB system
and that
mongo is an interactive JavaScript shell interface to MongoDB
but what does that mean practically? I presume every time I want to use mongodb, I need to run mongod first. But then why am I able to run mongo without having started mongod first? Does mongo run mongod in the background automatically? Secondly, if I run mongod it eventually ends with something like
waiting for connections on port 27017
but then I can't type anything after that. Again, I presume that mongodb has been started in the background so I can safely close the terminal. But if I close the terminal by mistake (on a mac), how can I get that back up on the terminal? Also, how can I terminate the service for it to stop listening to the port?
So as you can I see, I have a bunch of simple questions... but most are related to the practical uses of when and when not to mongo or mongod. I can't seem to find anything online that will help me explain these in the practical sense.
As with most database software, Mongo is split into a server and client. The server is the main database component which stores and manages data. Clients come in various flavours and connect to the server to insert or query data.
mongod is the server portion. You start it, it runs, end of story.
mongo is a default command line client. You start it, you connect to a server, you enter commands, you quit it.
You have to run mongod first, otherwise you have no database to interact with. Simply running mongod on a command line will make it the frontmost running application, and it does not offer any interactivity. So yes, you'll just see something like "Waiting for connections...", and nothing more. You typically don't run mongod like that on the command line. You most typically create an init.d script or launchd file or however you manage your daemons, and have the system start it automatically at system boot time.
If you want to launch mongod as a one-off thing without having it permanently running on your systems, put it in the background:
$ mongod &
The & puts it in the background and you can continue to use your command line. You can see it and kill it like this:
~ deceze$ mongod &
[1] 1065
~ deceze$ jobs
[1]+ Running mongod &
~ deceze$ kill %1
[1]+ Done mongod
Once your server is running, start mongo, connect to the server, and interact with it. If you try to run mongo without a running server, it should complain that it's not able to connect:
~ deceze$ mongo
MongoDB shell version: 3.0.2
connecting to: test
2015-08-13T09:36:13.518+0200 W NETWORK Failed to connect to 127.0.0.1:27017, reason: errno:61 Connection refused
2015-08-13T09:36:13.521+0200 E QUERY Error: couldn't connect to server 127.0.0.1:27017 (127.0.0.1), connection attempt failed
at connect (src/mongo/shell/mongo.js:179:14)
at (connect):1:6 at src/mongo/shell/mongo.js:179
exception: connect failed
If your mongo shell does connect to something, you might unknowingly have another instance of mongod running on your system.
With mongodyou are starting the server on your machine. As you stated correctly, mongo is your client, your user interface, if you want to. Per default it connects to your local instance of MongoDB. If you start your client without a server instance running, you would have to 'tell' it, where it should connect to (e.g. a remote instance):
http://docs.mongodb.org/manual/reference/program/mongo/
Related
I sometimes can start the mongodb server and sometimes I cannot. What is the real problem with my mongodb server. I am using Mac and I am getting this problem for the first time.
I tried to kill the mongodb process but it didn't help me.
Any possible solutions would be highly appreciated.
The error I am getting is below.
For killing the process, I tried to kill 27017 and it says no process found.
I think you are confusing port and PID. When you kill 27017, you send the SIGKILL signal to a process whose PID is 27017. However, unless there is a coincidence, mongod does not need to have that PID. 27017 is the default port for mongod instances.
To kill it properly do the following:
ps -edf | grep mongod --> get the PID of the mongod process
Then:
kill -SIGKILL <pid>
Then start it again.
I'm using Ubuntu 16.04, and I can't understand what's difference between using
sudo service mongod start
and
mongod
In mongodb official documentation here
said that to start mongodb just use sudo service mongod start, and its log stores in /var/log/mongodb. However, I try to run mongodb using mongod this way, log shows on terminal, and after I turn off the terminal, I can not find the log file.
It is confused.
sudo - Runs the command as root.
service - Manages the following program as a daemon (background process).
mongod - Obviously the MongoDB program in question.
start - A command that tells service what to do with the program in question.
Together, we get "I want to start mongod as a background process, and I want to run it as root so it has permission to do the things it needs to do". Running mongod by itself, however, runs the program in an ordinary fashion, i.e. as a foreground process. Typically you want to run it as a background process so that you're free to do other things, e.g. connecting to the database via shell access.
This is pretty simplified, but it should explain what you actually need to know at this point in time.
I have installed mongodb in my computer. But whenever I try to launch it, it's not running. I have entered command , as "mongo" to start the mongodb, which shows following resuts, but the application is not opening.
Any one having any idea how can I fix this? Please share it. Thanx!
Environment: Ubuntu 16.04
Those are warnings that appear at the first mongo start. Don't worry to much about them.
Since the process is still running and you got the small > character there, that means you successfully connected to the MongoDB server.
mongod is the MongoDB server (you can check if it's running by running ps aux | grep mongod) and the mongo cli tool is a cli client connecting to the server. Here you can run commands.
For example, create your first document:
use myDatabase
db.people.insert({ name: "Rhea" })
db.people.find()
In conclusion, both the MongoDB server and client are running but you got a few warnings that only appear the first time when you run mongo.
Initially in one terminal write mongod.
Then on another terminal : mongo .
The first one will start the mongo server.
The second one will start the interpreter.
You can try various commands in the interpreter.
I am new to MongoDB and trying to install MongoDB on Windows 8.1.
After I finished the .msi installtion and prompt C:\Program Files\MongoDB\Server\3.4\bin\mongod.exe -dbpath E:\MongoDB\data\dbon CMD command, where the folder E:\MongoDB\data\db has already been created manually.
After I input that command on CMD, it seems that the program stops at [thread1] waiting for connections on port 27017 and does nothing for a long time.
So anyone knows what's wrong and how to fix it?Many thanks.
As stated in this Documentation, the waiting for connections on port 27017 means that mongoDB is running succesfuly(server instance).
You will need to connect to MongoDB through mongo.exe shell using another CMD instance (client instance).
The waiting message in first console would change to connection accepted, and you can start working on your client side.
Running MongoDB Shell v-3.2.8
I've noticed that articles and tutorials always mention to run the mongod server before running the mongo shell.
However, when I skip the first step and simply type mongo into my terminal, the mongo shell works without any errors / interruptions.
MacBook:Desktop user$ mongo
MongoDB shell version: 3.2.8
connecting to: test
Why does this work? Does mongo call mongod?
The mongod is being ran as a service or daemon, which means that there is always a mongod process running listening to a port. I use ubuntu, and when I install mongodb through the package manager, it immediately starts up a mongod process and begins listening on the standard port.
Running mongo is simply a small utility that attempts to connect to the localhost at the standard ip. The data reading, writing, and querying is done by the mongod process while mongo is a small program that sends the the commands to mongod.
If mongod wasn't running, you would see an error stating "Unable to connect to mongodb server"
I noticed the same. I think mongoose is doing some smart things there, which I'm not sure how it works. But I have noticed such things before, like mongoose will automatically add an "s" to your database's name when you declare it, which is a very thoughtful act =)).
I encountered the same thing and found that in the background services if MongoDB server is running, the mongo shell will work without any error. If we stop the service, the shell will throw an error.