TL;DR: lots of history, some explanation of why things are done certain ways. | From: o1bigtenor via talk <talk@gtalug.org> | OK - - - good to know. For many years it was | /boot, Covered well by Lennart. This first came up for me with UNIX System V release 2 on a PC. The boot loader only understood a a special simple file system (BFS). This file system was pretty useless for real work so only a minimal set of stuff was held there. I *think* it was mounted as /boot. It was a lot like the kernel + initrd. There's an interesting bootstrap problem that it addresses: how simple can you make the bootloader and still make it do what you need. LILO was an elegantly simple solution but it pinched: - It used BIOS for disk I/O. Eventually BIOSes could not address the whole of a disk and this bizarre limitation bled into the bootloader. - The bootloader did not understand any filesystems so a tool was needed to put absolute disk addresses into the bootloader whenever a kernel or initrd was moved, added, or deleted. Forget to do this and your system became unbootable. - Secure Boot? I don't see how that could fit into the LILO framework. - UEFI? I think that a new bootloader, as simple as LILO, but a lot better, could be written using the API provided by UEFI. GRUB is quite complex. Among other things, it needs to understand any filesystem from which it can boot. For another, it needs its own disk device drivers so that it can get around the BIOS limitations outlined above. I have a little PC that has a too-small "disk" (eMMC) to hold Windows and Linux. I wanted to use an SD card to hold Linux. The UEFI firmware doesn't have a driver for the SD card. So the machine cannot boot from the SD card. If GRUB had such a driver, then I could put /boot on the SD card, but it doesn't. Still, it would be quite reasonable for it to have such a driver. | / (or /root), Those are quite different. / is the root filesystem /root is the home directory for user "root". It is conveniently on / so the root user can be logged in without /home being mounted. | /usr, /var, /tmp, | swap, /usr/local and /home. I've had enough issues because / was too small, | ditto for /usr. If you use LVM (I don't) you get a level of indirection that lets you increase partition sizes pretty freely. So you don't have to get allocations right at the beginning. /tmp is quite reasonably on a separate special-purpose filesystem. On Fedora 28, the default is to use the filesystem type "tempfs". In the days of LILO, /boot needed to be addressable by LILO so it was constrained. That was one reason to put /boot in a separate filesystem. Once upon a time, / was all you needed for single user mode. You kept everything else in things like /var and /usr so that there was a great chance that a broken system could still be booted in single user mode. / was almost, but not quite, read-only. Long gone. Sometimes fleets of boxes shared, say, /usr, through NFS. This meant some kinds of system administration were easier and disk resources were less wasteful yet each machine was faster than a diskless workstation. Now /, /var, /usr/var, /local, /usr/local, /bin, /opt, might as well be on one filesystem. I keep /home separate so that my user data is mostly in its own filesystem. Then replacing the OS is almost simple. Too bad the dotfiles need to adjust for different OSes. | So on a new system I can drop /boot and only add /efi or ???? /boot/efi, not /efi. Of course that isn't the name of the filesystem it is the mount point. (Some people insist on using BIOS, not UEFI. In that case, you probably want a separate /boot and no /boot/efi. I think UEFI is a better choice.)