Question

IS there a way that we can calculate how many ‘mongod’ instances are running on a single ubuntu server at a given time.

Answer 1

On Ubuntu, the ps output of a running mongod process will look something like this –

mongodb 2210 3.3 1.5 259012 15300 pts/0 Dl 11:48 0:00 mongod –dbpath /var/tmp/mongotest –logpath /var/tmp/mongotest_log –port 3001

so you can follow Sergio’s solution. If you want to exclude the config server element (as it’s a mongod process also, see my comment)

Another way of checking would be to run –

ls /etc/mongodb*conf | wc -l

as each mongod instance should (if it’s installed as per recommended) its own configuration file under etc, e.g. /etc/mongodb.conf, /etc/mongodb1.conf, /etc/mongodb2.conf etc.

Each mongod instance will have its own logpath and datapath, which you should find configured in the relevant configuration file under etc. For example –

# mongodb1.conf

dbpath=/var/lib/mongodb1

#where to log
logpath=/var/log/mongodb/mongodb1.log

port = 30001

so the previous command will also apply.

ls /var/lib/mongodb* | wc -l

ls /var/log/mongodb/mongodb*log | wc -l

You may be interested in my answer on dba.stackexchange.com for more information on how to run multiple mongodb instances on Ubuntu using Upstart.