mirror of
https://github.com/troglobit/finit.git
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Joachim Wiberg
57c97d8190
This adds support for bringing up the system with an alternate fstab at boot. E.g., when using a primary/secondary setup for boot partitions. By default /etc/fstab is read, like before, this can now be changed using configure --with-fstab=/path/to/fstab.primary, which sets the default that can be overridden using finit.fstab=/etc/fstab.secondary If mounting, or fsck, fails in any way, Finit calls its own bundled sulogin, or the system sulogin(8), to let the user handle the issue. If there is no sulogin available, Finit will try to start up in its rescue.conf boot mode. Please note, in either of these rescue modes, use `reboot -f` to get the system to reboot. Finit is on pause in the background in rescue mode and cannot be relied on (since there may not be any writable filesystems available.). Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
77 lines
3.4 KiB
Markdown
77 lines
3.4 KiB
Markdown
Tips & Tricks with the kernel cmdline
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=====================================
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This document summarizes the different boot parameters that can be
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passed on the Linux kernel command line. Not limited to Finit.
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The `bool` setting is one of `on, off, true false, 1, 0`.
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> **NOTE:** remember to use `--` to separate kernel parameters from
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> parameters to init. E.g., `init=/sbin/finit -- finit.debug rescue`
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* `debug`: Enable kernel debug. Debug messages are printed to the
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console until Finit starts up, unless `loglevel=7` (below) is used.
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* `finit.debug[=bool]`: Enable finit debug. This is operated
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independently of the kernel `debug` setting. New as of Finit v4.
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* `finit.fstab=</path/to/etc/fstab.alternative>`: Tell Finit to use an
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alternate `fstab` to mount the file system from. Remember, this file
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must be on the `root=...` file system provided to Finit from the
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kernel. By default the built-in fstab is used, which itself defaults
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to `/etc/fstab`, but can be changed at build time with:
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./configure --with-fstab=/path/to/fstab
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It is even possible to disable a built-in default using:
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./configure --without-fstab
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Making `finit.fstab=/path/to/fstab` a *mandatory* command line option.
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Note, if the command line fstab is missing, Finit falls back to the
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built-in fstab, and if both are missing, the system treats this as a
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bad `fsck` and thus calls `sulogin`. If, in turn, `sulogin` is not
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available on the system, Finit calls reboot, which is also what will
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happen when a user exits from `sulogin`.
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* `finit.status[=bool]`: Control finit boot progress, including banner.
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(Used to be `finit.show_status`, which works but is deprecated.)
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* `finit.status_style=<classic,modern>`: Set Finit boot progress style,
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when enabled.
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* `init=/bin/sh`: Bypass system default init and tell kernel to start a
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shell. Note, this shell is very limited and does not support
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signals and has no job control. Recommend using, and modifying,
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`rescue` mode instead.
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* `loglevel=<0-7>`, sets the kernel's log level, which is more granular
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than `debug`. Also, when `loglevel=7`, Finit will *not disable*
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kernel logs to the console. This is very useful when debugging the
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kernel at system bring-up. Since `loglevel=7` is the same as `debug`
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this means you have to use `quiet` for a quiet boot, until sysklogd
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takes over logging of kernel events.
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* `panic=SEC`: By default the kernel does not reboot after a kernel
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panic. This setting will cause a kernel reboot after SEC seconds.
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* `quiet`: Suppress kernel logging to console, except for warnings and
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errors. Also, see `loglevel` and `quiet` above.
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* `rescue`: Start rescue/maintenance mode. If your system comes with
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the bundled `sulogin` program (Finit, or from util-linux/Busybox),
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you will be given a root login to a maintenance shell. However, if
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`sulogin` is missing, the file `/lib/finit/rescue.conf` is read and
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the system booted in a limited fallback mode. See [config.md][]
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for more information.
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* `single`, or `S`: Single user mode, runlevel 1, in Finit. Useful to
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debug problems with the regular runlevel. All services and TTYs in
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`[1]` will be started, so a `tty [1] @console nologin` configuration
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presents you with a root console without login.
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For more on kernel boot parameters, see the man page [bootparam(7)][].
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[config.md]: config.md#rescue-mode
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[bootparam(7)]: https://www.man7.org/linux/man-pages/man7/bootparam.7.html
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