It has been a while since I have used Mongodb and I am running into a problem. I have an EC2 instance that had Mongodb running on it, but I had turned off the instance for a few months. After turning the instance back on, Mongodb will not start correctly. No log file is being created so I do not know what is causing the problem.
When I type:
sudo service mongodb start
I get the message:
mongodb start/running, process 2432
but mongo is not actually running and a mongod.lock file is being created.
If I type:
mongod
by itself, Mongodb will actually start and be usable. But, I must leave the terminal window up and not cancel out of the command to keep it running. I have to open up a second terminal window to access my databases. I guess my main question is how I get the mongod service to stay running itself without having to leave a terminal window open with the command running.
Sorry if my explanation doesn't make sense. Hopefully you get what I mean. Anyone have any idea what I am missing? I had this problem before months ago and was able to solve it. Sadly, I didn't write down the missing ingredient.
For that, run command using Nohup
nohup mongod &
Then you can terminate you terminal.
Related
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.
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.
I am using Ubuntu 14.04 LTS and I have installed MongoDB 3.2.1. I had various problems with it that I fixed by either finding help from the internet (thanks Google) or by uninstalling and re-installing MongoDb.
One persistent problem that I cannot fix, unless I re-install, is by running mongod on the terminal. Currently my mongodb installation is working properly. With sudo service mongod start I start mongodb (I commented out start on xxxx line at /etc/init/mongod.conf so it doesn't auto start.) and with sudo service mongod stop I can stop it normally atm. And it correctly uses /var/lib/mongodb path for saving my collections.
If however after I stop mongodb with sudo service mongod stop I hit, on the terminal, mongod then mongodb breaks. I have gotten all kinds of errors like
Unusable mongod.lock. I have gotten around it, in a previous install, by doing sudo mongod but that was not a proper solution.
/data/db folder not found !!. Why look for it in the first place? The /etc/mongod.conf specifies the dbpath /var/lib/mongodb which is also the default when mongodb gets installed !!?? I have gotten around it as well with the mongod --dbpath /var/lib/mongodb option.
I think there was one more error that I don't remember but I also fixed/gotten_around it by finding solutions online.
I know that by re-installing and by never running mongod I can - for now? - not face those problems again (which looks a much better solution that the "workarounds" I did whenever those problems arose. I am wondering however what it is that is going wrong when I type mongod instead of sudo service mongod start ?!
In case somebody tries to replicate the problem know that I ve done only two modifications on my system after installing:
Commenting out the start on xxxx line at /etc/init/mongod.conf
Disabling transparent hugepages as described on the answer here.
I don't think anyone of those should interfere with my installation.
Can anyone help me understand what is going on? Aren't those commands supposed to do the same thing??
Thanks for your help.
Ok, I will try to answer.
First, unless you know what you are doing, you should not start mongod manually.
In general (a bit simplified), calling [sudo] service mongod start, you instruct the system to read the according file in /etc/init and start the executable according to the configuration described in said file.
When you started mongod by hand, however, you actually called the mongod binary, the server software itself – while the name is the same as the service, the two commands have few things in common. The binary does not use the /etc/mongod.conf by default, falling back to its default values for the various settings. Actually, you can see that the config file is explicitly defined in the init script. This is why mongod tried to find /data/db.
You can find said binary by issuing
which mongod
Regarding the lock file: When mongod is started by the system, user root actually assumes the effective user id of mongod (or mongodb I don't know for Ubuntu of the top of my head). When you tried to start it from your user id, you do not have the privileges to overwrite the lock file. When you used sudo mongod afterwards, you assumed the effective user id of root which on the other hand is allowed to overwrite said file. However, mongod will the run as root which is a security no-no.
An init script defines which environment to use, which user to run under and a lot of other stuff. Unless you really know what you are doing, you should not even fiddle with them, much less skip it.
And now, with the finger up
sudo is not the UNIX way of saying "I mean it!"
It has security implications, and you should be very aware of those implications before using it – aka read the man pages of every command you issue before you use it until you have at least a fact based idea of what the command is doing.
And again: unless you really know (as opposed to assume) what you are doing, do not fiddle with the system configuration.
I am new to Mongodb. When I run the following command:
sudo service mongodb start
It shows me "mongodb start/running, process 3566". But when I try to stop by giving the below command:
sudo service mongodb stop
It shows stop: Unknown instance:. Do anybody have any idea how to slove this issue.
And if I give sudo service mongodb restart, I'm getting the below message:
stop: Unknown instance:
mongodb start/running, process 3644
PS: If I'm using just mongod, I could start the server and could connect the mongo shell by giving mongo.
Please suggest me how to fix the issue and how to connect mongo shell after giving service mongodb start. Thanks in advance.
I just ran into this.
Chances are the issue is in your conf file (obviously, since you reinstalled the seeded)
In the mongodb.conf do not set fork = true if calling it as a service. This will prevent the service call from being able to access it with service mongodb.conf status/stop/restart.
Removing a fork=True line, however, will alleviate the issue.
See comments; use the other solution even though this one is accepted.
The reason you get the Unknown instance error is because upstart is tracking the wrong PID for the instance of forked mongod process. But the proper solution to this is not running the process in foreground by removing fork=true line from the config like #GoingTharn suggesting, but rather helping upstart to capture the right PID of the forked process by adding
expect daemon
to the /etc/init/mongodb.conf
I faced exactly the same problem and did the followings:
Removed the file mongod.lock (in my case this file was located at /var/lib/mongodb/)
Used the following command from my mongo client
mongo --repair
And that fixed the issue. It may be noted that I had a system crash prior to this problem appeared. Therefore, what I believe, the problem was caused due to the unclean shutdown of the server demon.
If you are unsure of the reason, you may wish to have a look at the log file (in my case I found it under /var/log/mongodb/). That might give you some useful hints.
Thanks.
I faced it as you had.Maybe it is because my computer crash unexpectedly.I use the command: sudo top(ubuntu), and I found mongo running.I killed it and start mongo.Every thing turns right.
I fixed it by myself. Below is what I did:
apt-get install mongodb
And overwrote .conf file. After that everything works fine. I hope this would help someone.