Custom Embedded Linux Distributions
In the past, many embedded projects used off-the-shelf distributions and stripped them down to bare essentials for a number of reasons. First, removing unused packages reduced storage requirements. Embedded systems are typically shy of large amounts of storage at boot time, and the storage available, in non-volatile memory, can require copying large amounts of the OS to memory to run. Second, removing unused packages reduced possible attack vectors. There is no sense hanging on to potentially vulnerable packages if you don't need them. Finally, removing unused packages reduced distribution management overhead. Having dependencies between packages means keeping them in sync if any one package requires an update from the upstream distribution. That can be a validation nightmare.
Yet, starting with an existing distribution and removing packages isn't as easy as it sounds. Removing one package might break dependencies held by a variety of other packages, and dependencies can change in the upstream distribution management.
Read more at Linux Journal