MongoDB, an Ubuntu user other than root, and storing the PID file in /var/run/mongodb

Question

I am having trouble storing the PID file for mongod in the directory /var/run/mongodb and getting the mongod process to start on boot as a user other than root .

I have installed MongoDB v2.6.3 on Ubuntu v14.04; created a linux user called mongodb ; and granted ownership of the directories in the following configuration to that user, using chown -R mongodb:mongodb {path} :

systemLog:
  path: /var/log/mongodb/mongod.log
  logAppend: true
  destination: file

processManagement:
  pidFilePath: /var/run/mongodb/mongod.pid
  fork: true

security:
  keyFile: /srv/mongodb/keyfile
  clusterAuthMode: keyFile

storage:
  dbPath: /data

replication:
  replSetName: myReplicaSet

I understand that only the root user can write to the /var/run directory, so I added the following code to /etc/rc.local in order to create a subdirectory that my mongodb user owns:

PID_FILE_DIRECTORY=/var/run/mongodb
CONFIG_FILE=/etc/mongod.conf

do_start () {
  if [ ! -d $PID_FILE_DIRECTORY ]; then
    mkdir $PID_FILE_DIRECTORY
    chown -R mongodb:mongodb $PID_FILE_DIRECTORY
  fi
  setuid mongodb
  mongod -f $CONFIG_FILE
}

exit 0

When I reboot the server, I expect mongod to start as if the user mongodb had run the mongod command. However, when I check the logs I see the error:

ERROR: Cannot write pid file to /var/run/mongodb/mongod.pid: No such file or directory

I noticed in /etc/init.d there was a file called mongod that appeared to be overriding my commands in rc.local (a default boot script for MongoDB that I can't seem to find any documentation on). Feeling brave, I deleted that file, rebooted the server, and got the same error as above.

Frustrated, I shutdown the server and went to bed. The next morning, I woke up, booted the server, and everything worked as expected. The mongod process was running; the directory /var/run/mongodb existed; everything was fine.

However, when I rebooted the server I again got the error message.

What is happening here?? Is rc.local not being run on reboot? If so, how can I get it to do so? Is there a better way of achieving my goal?

Answer 1

Turns out the preferred way to handle startup services in Ubuntu is by using upstart configuration files , which are located in /etc/init .

Looking at /etc/init/mongodb , I found a section that looked like this:

pre-start script
    mkdir -p /var/lib/mongodb/
    mkdir -p /var/log/mongodb/
end script

To which I added:

mkdir -p /var/run/mongodb
chown -R mongodb:mongodb /var/run/mongodb

And that seemed to do the trick!