How to Install MongoDB 4.0 on Arch Linux

Prerequisites

• A FastyCloud server running up to date Arch Linux (see this article)
• Sudo access:
  • Commands required to be ran as root are prefixed by #, and ones that can be ran as a regular user by $. The recommended way to run commands as root is to, as a regular user, prefix each of them with sudo.

Install MongoDB 4.0 Database

MongoDB is in the AUR (Arch User Repository). There are 2 sets of packages you can use. See Building Packages on Arch Linux (Including the AUR) to compile and install either set of packages:

1. Compile from source. Use AUR packages mongodb and possibly mongodb-tools‘. Note this takes about 180GB, and this is a long compilation. With 4 cores, it takes about 7 hours. This is the recommended method, because it uses Arch’s compilation flags.
2. Use MongoDB’s pre-built binary. Use AUR package mongodb-bin and possibly mongodb-tools-bin. This skips the entire compilation stage, downloading a pre-built binary from mongodb.org, and packaging it with the necessary configuration files.

After installing the package, start MongoDB, and make it start after every boot. During this first start, it will pre-allocate files for its journal and other data, which may take a while before the database finishes coming up:

# systemctl enable --now mongodb

Test Connection

Connect to MongoDB:

$ mongo

To quit:

> exit

Firewall Consideration

Although configuring a firewall is always a good idea, by default, MongoDB only listens on port 27017 on localhost, so it will receive no external traffic.

Require Authentication

By default, MongoDB allows anyone to connect to it without any type of authentication, which is obviously a security risk.

Create a root database user:

$ mongo
> use admin
> db.createUser(
... {
... user: "root",
... pwd: "YOUR-NEW-PASSWORD",
... roles: [ { role: "userAdminAnyDatabase", db: "admin" }, "readWriteAnyDatabase" ]
... }
... )
> exit

Edit /etc/mongodb.conf, and if using package mongodb add:

security:
  authorization: "enabled"

If using package mongodb-bin add:

auth = true

Restart MongoDB:

# systemctl restart mongodb

Now, although you can still connect to MongoDB without authentication, it will not perform anything without it:

$ mongodb
> db.getUsers()
... Error: command usersInfo requires authentication :

Connect to MongoDB as root:

$ mongodb -u root

Alternatively, connect to MongoDB, then authenticate within it:

$ mongodb
> use admin
> db.auth("root", "<YOUR-DATABASE-ROOT-PASSWORD>")

Important: Upgrades

Because MongoDB is now part of the AUR, pacman will not automatically compile and upgrade it to new versions, when you upgrade your entire Arch system. You will need to manually re-compile a new version and install the new package. Before doing so, it is important to look at MongoDB’s release notes, to see if there are any extra steps you need to take. It’s a good idea to backup your database before upgrading, as well.

Unclean Shutdown

If MongoDB does not cleanly shutdown, and does not automatically recover using its journal on the next boot, you may need to run the following:

sudo -u mongodb mongod --repair --dbpath /var/lib/mongodb/

Depending on the size of your database and indexes used, this process can range from seconds to hours.