I'm trying to understand how the operating system (OS) can be mounted on a filesystem when it seems like the filesystem is just a feature of the OS itself. It feels like an endless loop of components working together—where does it all start? What's the sequence that takes place during booting?
4 Answers
To clarify, the OS is a general term covering several components: the kernel, desktop environments, and distributions (distros). The boot process involves the UEFI loading the bootloader which can navigate various filesystems. The kernel is loaded into memory after the bootloader mounts the filesystem it’s stored on, which includes the necessary info to know about the root filesystem. This process helps the kernel effectively handle commands and structure once it’s running.
When you boot up your computer, it all starts with the BIOS or UEFI. This initial firmware points to the bootloader stored on your drive, often something like Grub. The bootloader then loads the necessary components into RAM, including the kernel and an initial RAM disk (initramfs). The kernel is what can then interact with filesystems and mount the root filesystem to continue the boot process. Essentially, the bootloader kicks everything off and tells the kernel what filesystem to use as the root. It's kind of like a chain reaction, with each part leading to the next!
Exactly! And modern UEFI setups can even load kernels directly, but most still use a bootloader.
Booting is often referred to as 'bootstrapping'. The initial boot process uses a small program in the motherboard to find and run the bootloader, which then handles the heavier lifting of loading the OS and mounting the filesystem. Each part builds on the last, and eventually it all leads to the kernel being in charge, managing the filesystem among other things. It’s basically a sequence of tiny steps that all connect to get the system running!
And each step relies on the previous one, right? So if one fails, it affects everything?
Exactly! If the bootloader can’t find the kernel, the whole system won’t boot.
The phrase 'bootstrapping' indeed comes from the old saying about pulling oneself up by the bootstraps. It’s this process of gradually loading just enough to get the next component up and running, until the full OS is operational. The BIOS/UEFI for checking hardware, then the bootloader loading everything it needs—all the way until you have a fully operational system!
Got it! So the kernel doesn’t load itself; it’s the bootloader that does all that work first.