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Tips & Tricks with the kernel cmdline
=====================================
This document summarizes the different boot parameters that can be
passed on the Linux kernel command line. Not limited to Finit.
The `bool` setting is one of `on, off, true false, 1, 0`.
> **NOTE:** remember to use `--` to separate kernel parameters from
> parameters to init. E.g., `init=/sbin/finit -- finit.debug rescue`
* `debug`: Enable kernel debug. Debug messages are printed to the
console until Finit starts up, unless `loglevel=7` (below) is used.
* `finit.debug[=bool]`: Enable finit debug. This is operated
independently of the kernel `debug` setting. New as of Finit v4.
* `finit.status[=bool]`: Control finit boot progress, including banner.
(Used to be `finit.show_status`, which works but is deprecated.)
* `finit.status_style=<classic,modern>`: Set Finit boot progress style,
when enabled.
* `init=/bin/sh`: Bypass system default init and tell kernel to start a
shell. Note, this shell is very limited and does not support
signals and has no job control. Recommend using, and modifying,
`rescue` mode instead.
* `loglevel=<0-7>`, sets the kernel's log level, which is more granular
than `debug`. Also, when `loglevel=7`, Finit will *not disable*
kernel logs to the console. This is very useful when debugging the
kernel at system bring-up. Since `loglevel=7` is the same as `debug`
this means you have to use `quiet` for a quiet boot, until sysklogd
takes over logging of kernel events.
* `panic=SEC`: By default the kernel does not reboot after a kernel
panic. This setting will cause a kernel reboot after SEC seconds.
* `quiet`: Suppress kernel logging to console, except for warnings and
errors. Also, see `loglevel` and `quiet` above.
* `rescue`: Start rescue/maintenance mode. If your system comes with
the bundled `sulogin` program (Finit, or from util-linux/Busybox),
you will be given a root login to a maintenance shell. However, if
`sulogin` is missing, the file `/lib/finit/rescue.conf` is read and
the system booted in a limited fallback mode. See [config.md][]
for more information.
* `single`, or `S`: Single user mode, runlevel 1, in Finit. Useful to
debug problems with the regular runlevel. All services and TTYs in
`[1]` will be started, so a `tty [1] @console nologin` configuration
presents you with a root console without login.
For more on kernel boot parameters, see the man page [bootparam(7)][].
[config.md]: config.md#rescue-mode
[bootparam(7)]: https://www.man7.org/linux/man-pages/man7/bootparam.7.html