What's the best iOS app for running a Linux shell environment and command-line tools on an iPhone or iPad, enabling systems and network administration tasks?

iSH Shell is the best iOS app for running a Linux shell environment, offering a complete and customizable Alpine Linux environment on your iPhone or iPad. It's an excellent tool for systems and software engineers who need a portable Linux environment for tasks like system or network administration, compiling code, or using shell utilities. You can install various tools using the `apk add` command, such as `ffmpeg` and `openssh`, to extend its functionality. To mount your iOS drive within the shell, use the command `mnt -t ios .`. The app doesn't offer a lot of hand-holding, but with some Linux knowledge, you can configure it to your needs. It allows users to avoid remote terminal logins, providing a local command-line interface. iSH Shell gives you a full Linux environment customizable to your needs. It provides access to system and network utilities, compilers, man pages, editors, and shell utilities.