how to upgrade MongoDB 2.6 to 3.x on Ubuntu

sudo mv /etc/apt/sources.list.d/mongodb* /tmp/
echo "deb "$(lsb_release -sc)"/mongodb-org/3.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.0.list
sudo apt-get update && sudo apt-get install -y mongodb-org

And I also had to do fix my replica set in the MongoDB shell (necessary for Meteor oplog tailing):

var a = {"_id" : "rs0", "version" : 1,"members" : [{"_id" : 1, "host" : "localhost:27017"}]};
rs.reconfig(a, {force:true});

UPDATE 2015-10-01: Alas, one of my coworkers found even all the above wasn’t enough–he had to blow away his old MongoDB install.

sudo mv /var/lib/mongodb /tmp
sudo apt-get purge mongodb-org-server
sudo apt-get install -y mongodb-org-server

We also use one-member replica sets in dev (Meteor uses the oplog), so edit /etc/mongodb.conf and include something like replSet=rs0, then restart mongo (sudo service mongodb restart). Finally, initialize the replica set:

var a = {"_id" : "rs0", "version" : 1,"members" : [{"_id" : 1, "host" : "localhost:27017"}]};

It appears that collections can be restored by simply copying files like blah.0, blah.1, blah.2 and blah.ns from /tmp/mongodb to /var/lib/mongodb while the MongoDB server is stopped.

Ubuntu and Encryption

Encryption is a nice security feature that makes it significantly harder for someone to mine your data if, for instance, your latptop is stolen.

If you install Ubuntu with the alternate installer disk, encryption takes only a few keystrokes. Here are two tutorials with screenshots.

If you only need to encrypt a single file, just right-click on the file in the File Browser and click “Encrypt”.