When comparing SysV-init vs runit, the Slant community recommends SysV-init for most people. In the question“What are the best Linux init systems?” SysV-init is ranked 2nd while runit is ranked 3rd.
Ranked in these QuestionsQuestion Ranking
Pro Simple to understand
Pro Very stable
Since sysvinit does only one thing (initialize the system) and one thing only, it's very stable and it's impossible for it to fail for any problems unrelated to booting the system.
Pro Better boot time and overall performance
Pro Fast, parallel startup
After the system's one time tasks (stage 1) are done, the system services are started up in parallel. The operating system's process scheduler takes care of having the services available as soon as possible.
Pro Small and Unix-like
One of the runit project's principles is to keep the code size small. As of version 1.0.0 of runit, the runit.c source contains 330 lines of code; the runsvdir.c source is 274 lines of code, the runsv.c source 509. This minimizes the possibility of bugs introduced by programmer's fault, and makes it more easy for security related people to proofread the source code.
The runit core programs have a very small memory footprint and do not allocate memory dynamically.
Pro Easy to use
Simple scripts linked to the proper directory is all that's needed to bring a service up at boot, and everything is up and running quickly.
Pro Runs on every POSIX system
Pro Supported by several Linux plumbers
Myself included. Development is no longer stalled.
Pro Init purity. Does what an init system must do and nothing more.
UNIX philosophy, easy to add new services, easy to manipulate, really fast,
Happy to read, that the development is not stalled.
Con Launches a bunch of processes to launch a process
Every init script spawns at least sh/dash/bash, and probably also additional processes such as cat, echo, start-stop-daemon, etc, just to start a single daemon that may not even be needed at the time of boot. This massive overhead results in poor performance, and is a killer for embedded systems.
Con Can lead to slow boot
Since init starts tasks serially, it has to wait for a certain task to finish in order to start the next one. But when startup processes end up I/O blocked, this leads to considerable delays during boot.
Con Duplicated implementation for every service
Every init script needs to reinvent the wheel for every script: argument processing, start/stop/restart/reload/status/whatever processing, finding/clearing/creating PID files, sourcing defaults, building and setting configuration options, so on and so forth.
Con Initscripts is not portable
It is virtually impossible to write portable sysvinit-scripts
Con Hard to write sysv-initscripts
As one needs programming skills (opposed to a declarative style).
Con Development stalled
Last patch was back in 2014.