root/sudo access is not available on DreamHost managed servers (Shared, VPS, and DreamPress plans). The only exceptions are Dedicated Servers and DreamCompute.
Dedicated Servers allow root/sudo access. On this type of server, you can set up an admin user and install software using sudo.
Another option is DreamHost's cloud computing service, DreamCompute. This service is completely unmanaged meaning you can install whatever software you like on it.
DreamHost provides you with a base OS install (or you can even upload your own). On this machine, you can use sudo or log in as root. View the following article for further details:
Why is root/sudo access not available?
DreamHost currently manages all servers to provide quick and reliable updates necessary for the security and stability of the server. However, when users take server management into their own hands with the sudo command, it directly limits DreamHost's ability to provide a safe and reliable managed hosting environment. This is why it's only available on Dedicated Servers and DreamCompute which are isolated environments separated from other DreamHost users.
How can I install software and manage my sites without root/sudo access?
Most software does not need to be compiled into the operating system directly as root. You can generally install it to your user's home directory and run it as your non-root user. This can also be a more secure way to run these programs.
Below are a few examples with links that show how to manage your sites root/sudo access.
Changing PHP settings
PHP changes such as the following can be done using a PHP.ini file:
Installing PHP modules/tools/frameworks
PHP modules can also be installed locally. View the following for detailed examples: