Coda -- The Disconnectable File System

Brett Lymn

In a previous series of articles in Sys Admin, I mentioned Coda as a possible method to provide services to clients in the event of the server going down. However, I haven’t covered the installation of Coda because it was too involved for the topics I previously covered. In this article, I will cover the installation and configuration of a small-scale Coda server and client. Some of the setup of Coda presented here is only suitable for a small Coda cell, but this article should give you enough to get started experimenting with Coda and give you some experience that can be applied to larger Coda networks.

Coda is a file system descended from the AFS-2 sources that have been modified to provide features that were not available in the original implementation. The primary new feature is the ability of the client to be disconnected from the server and still use the mounted file system. This feature can be very handy if you have mobile laptops or an unreliable network. The users will have access to their work, within limits, regardless of whether the network connection is present. Unfortunately, Coda is still an experimental file system. The problem that Coda tries to solve involves some difficult situations that must be handled gracefully; currently, this simply does not happen in some cases, but improvements are constantly being made. The Coda server and client do work, but there is the risk that you will experience problems that may result in loss of data. Thus, having a good backup regimen, as always, is very smart.

Installing Coda for most systems is a matter of downloading the correct packages and loading them. In this article, I will cover the process for loading Coda onto a NetBSD machine; other operating systems will have other methods, but once the server and client are installed, the process of setting up Coda is the same.<>