Reply to post: systemd is not a boot loader

Linux greybeards release beta of systemd-free Debian fork

Flocke Kroes Silver badge

systemd is not a boot loader

The sequence is firmware loads (part of) the boot loader, which is usually grub for x86 or U-Boot for everything else. The boot loader - using nothing but itself and some probably broken firmware - loads the rest of itself, then the kernel (and possibly a small disk image). The kernel mounts the root file system, and then runs something as process 1. That was usually sysvinit, or - if you are recovering a badly confused machine - bash. Systemd is a replacement for sysvinit.

When process 1 starts, it has the complete kernel and any modules the kernel requires, the root file system, and probably a few pseudo file systems like /dev. Sys[vt][ei][nm][di]t? starts almost everything else: all the permanently attached file systems, any strange configuration, various demons, login for each terminal and one of the gui login programs. When a process dies, its parent gets sent a signal. If the parent is dead, that signal goes to process 1. While running, systemd/sysvinit restarts any dead demons. During shutdown, sysvinit/systemd kills all the processes and unmounts all the file systems.

This makes sys{vinit,temd} very different from a boot loader - which self destructed when it handed control to the kernel within a few seconds of power on.

BTW: Debian architecture names make sense to techies, but not to computer illiterates. AMD64 is almost certainly what your Intel processor is pretending to be when it is not pretending to be an ancient pentium for 32-bit Windows users. It is the most common architecture on the planet. Raspberry pi is odd. The earliest ones are not quite armhf. The newest ones are ARM64, and the ones in the middle are armhf. Supporting raspberry pi means armhf with restrictive compiler flags. Banana pi is full armhf, and anything armhf should be able to use the same repository.

If we go through popcon in order of architecture, fist is AMD64. Second is i386 (probably AMD64 compatible machines, although some will be ancient / odd). Raspberry pi is not included in popcon, but is probably next in real life, then comes armel (arm older than the oldest pi), powerpc (old converted macs?), armhf (banana pi, and a pile of other arm based small cheap computers). All the remaining architectures supported by debian together are not as common as armhf. Devuan have chosen about three and a half of the most popular architectures. The most of the others are too old to run Debian Jessie anyway, have bigger problems than hatred of systemd if the maintainers want to upgrade.

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