[rabbitmq-discuss] Question about erlang cookie

Priyanki Vashi vashi.priyanki at gmail.com
Tue Jul 23 10:01:08 BST 2013

Hi there ,

Thank you for answer on this.

I was away for few days so could not reply immediately. I had managed to
solve the problem.
It was on the similar lines as replied by Anton.

1) First I copied the single cookie in all the nodes. It was
/var/lib/rabbitmq path.
2) Another problem was that the nodes were able to identify each other only
by IP address and not by hostname and since in one of the post, I read its
necessary that nodes identify each other by hostname as well since when we
start nodes it picks node name. So edited /etc/hosts file on all the nodes
and added IP address and hostname.

Best Regards,

On Tue, Jul 23, 2013 at 10:23 AM, Anton Sizov <a.sysoff at gmail.com> wrote:

> hi
> 1) Probably installation created files with rabbitmq user ownes. It is not
> good practice to run rabbitmq server with root privileges. RabbitMQ need
> rights to read/write to mnesia and log dirs only. You can run RMQ with non
> root user.
> 2) Default place for .erlang.cookie file is user home directory. Probably
> at the installation RMQ places cookie in its installation dir
> (/var/lib/rabbitmq). Read
> http://www.erlang.org/doc/reference_manual/distributed.html and
> http://www.rabbitmq.com/clustering.html for more info about erlang cookie.
> 3) Your understanding is correct. RMQ uses only one cookie file. To be
> consistent you can delete one of them. Start with that placed in user home
> dir. Probably RMQ creates cookie in home dir when started not with rabbitmq
> user or not with init script (service rabbitmq strarted). I use precompiled
> RMQ package that place in /opt dir.
> 4) You doesn't I think. Different cookies can be the reason of such
> problems. To help you, it necessary to know
> - how you start rabbitmq node (1 and 2)
> - try to start nodes not in cluster on different servers with the same
> cookie and with the full name resolving (-name flag instead of -sname).
> Then try to get status of each node from it server and from another.
> [server1]# rabbitmq -n rabbtimq at server1 status
> [server1]# rabbitmq -n rabbtimq at server2 status
> [server2]# rabbitmq -n rabbtimq at server1 status
> [server2]# rabbitmq -n rabbtimq at server2 status
> It is minimum of actions to start resolve your problem.
> On Tuesday, July 2, 2013 1:42:37 PM UTC+3, Priyanki Vashi wrote:
>> Hi there ,
>> I had a question about erlang cookie, which gets generated when we start
>> rabbitmq server. The situation is as follows.
>> 1) Even if I did not created any user named 'rabbitmq', there are files,
>> which are owned by this user. Does the installation or startup of
>> rabbitmq-server does this ? Also is it OK to use root user to do server
>> administration operation or will it be considered not so good practice ?
>> 2) I use root user to start and stop rabbitmq server and when I start the
>> server, I see that a file .erlang.cookie gets generated in root home dir.
>> That is correct as per my understanding but I also see that there is
>> another file with the same .erlang.cookie gets generated in
>> /var/lib/rabbitmq
>> 3) Also these two erlang cookies are different from each other. Why there
>> are two erlang cookie files gets generated ? What is the importance ?
>> My theoretical understanding is there should be only one erlang cookie
>> should get generated and that one should be in home dir of user, which
>> starts the rabbitmq-server.
>> Is this correct understanding or ?
>> 4) Also do I need to configure different values of epmd ports when I want
>> to run cluster with two physical nodes or it's OK to keep it as default ?
>>     I thought NO need to change but then since I am running into these
>> problems thought of asking.
>> I would like to understand this bcoz, I tried to setup a cluster on two
>> different physical machines and as per the guidelines gives in 'rabbitmq in
>> action', before joining nodes running on different physical machines in the
>> cluster, the erlang cookie should be sync meaning that both the nodes
>> should have same erlang cookie so I tried to copy cookie from first node to
>> second and tried to restart second node but then I had problems with
>> restarting the node or even stopping the node and I get error. I also
>> checked the latest log file and it says
>> "=ERROR REPORT==== 2-Jul-2013::19:48:28 ===
>> ** Connection attempt from disallowed node rabbitmqctl40424 at nazgul **" ,
>> which I believe is due to the fact that erlang cookie, which it had
>> originally when I started the node has changed now and hence it does not
>> allow me to stop the node. Is my understanding correct here or ?
>> Error mesaage while stopping or restarting the node after copying erlang
>> cookie from first node to second one.
>> Error: unable to connect to node rabbit_2 at nazgul: nodedown
>> ===========
>> nodes in question: [rabbit_2 at nazgul]
>> hosts, their running nodes and ports:
>> - nazgul: [{rabbit_2,58454},{rabbit,**38771},{rabbitmqctl40424,**60952}]
>> current node details:
>> - node name: rabbitmqctl40424 at nazgul
>> - home dir: /var/lib/rabbitmq
>> - cookie hash: ad/NgkXjjR95x3cMejxwqg==
>> Thank you in advance and please guide me so that I understand what had
>> gone wrong here.
>> Best Regards,
>> Priyanki.
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