Amongst other things... if you want to remove everything you don't need. Make sure the filesystem has atime fully enabled, you can set this in /etc/fstab the current defaults is relatime but you want to use just atime. Everytime a file is access the timestamp will get updated. Then do some usage for a few days, to see which files have never had their atime updated. I would do all of this in a vm, and very carefully. because I imagine there are a few files that are read when the system is in read-only mode. note: set it to noatime once you're ready for production, otherwise you'll do a write everytime you read, this is inefficient.

Though to be honest, I'd look at Damn Small Linux do you really need to be smaller than that? build based on their distro and simply remove the window manager and a few extra programs.... leave all the command line tools, that way if you ever need to repair or reload you have the shell.

Amongst other things, you want to remove everything you don't need. Make sure the filesystem has atime fully enabled; you can set this in /etc/fstab. The current default is relatime but you want to use just atime. Every time a file is accessed, the timestamp will get updated. Then do some usage for a few days to see which files have never had their atime updated. I would do all of this in a VM, and very carefully, because I imagine there are a few files that are read when the system is in read-only mode. Note: set it to noatime once you're ready for production, otherwise you'll do a write every time you read; this is inefficient.

Though to be honest, I'd look at Damn Small Linux; do you really need to be smaller than that? Build yours based on their distro and simply remove the window manager and a few extra programs. Leave all the command-line tools, that way if you ever need to repair or reload you have the shell.