Manual: systemd-debug-generator

SYSTEMD-DEBUG-GENERATOR(8)			   systemd-debug-generator			  SYSTEMD-DEBUG-GENERATOR(8)

NAME
       systemd-debug-generator - Generator for enabling a runtime debug shell and masking specific units at boot

SYNOPSIS
       /usr/lib/systemd/system-generators/systemd-debug-generator

DESCRIPTION
       systemd-debug-generator is a generator that provides some debugging functionality.

       systemd-debug-generator implements systemd.generator(7).

KERNEL COMMAND LINE
       systemd-debug-generator understands the following kernel command line parameters:

       systemd.mask=, rd.systemd.mask=
	   These options take a unit name as argument. The unit specified is masked for the runtime (i.e. for this session —
	   from boot to shutdown), similarly to the effect of systemctl(1)'s mask command. This is useful to boot with
	   certain units removed from the initial boot transaction for debugging system startup. May be specified more than
	   once. The option prefixed with "rd."	 is honored only in the initrd, while the one without prefix is only honored
	   on the host.

	   Added in version 215.

       systemd.wants=, rd.systemd.wants=
	   These options take a unit name as argument. A start job for this unit is added to the initial transaction. This
	   is useful to start one or more additional units at boot. May be specified more than once. The option prefixed
	   with "rd."  is honored only in the initrd, while the one that is not prefixed only on the host.

	   Added in version 215.

       systemd.debug_shell, rd.systemd.debug_shell, systemd.default_debug_tty=, rd.systemd.default_debug_tty=
	   If the systemd.debug_shell or rd.systemd.debug_shell option is specified, the debug shell service
	   "debug-shell.service" is pulled into the boot transaction and a debug shell will be spawned during early boot. By
	   default, /dev/tty9 is used, but a specific tty can also be specified, either with or without the /dev/ prefix. To
	   set the tty to use without enabling the debug shell, the systemd.default_debug_tty= option can be used which also
	   takes a tty with or without the /dev/ prefix. Note that the shell may also be turned on persistently by enabling
	   it with systemctl(1)'s enable command. The options prefixed with "rd."  are honored only in the initrd, while the
	   ones without prefix are only honored on the host.

	   Added in version 215.

       systemd.break=, rd.systemd.break=
	   Takes one of pre-udev, pre-basic, pre-mount, or pre-switch-root (the default for the "rd."  option). It also
	   accepts multiple values separated by comma (","). These options allow one to pause the boot process at a certain
	   point and spawn a debug shell. After exiting this shell, the system will resume booting. The option prefixed with
	   "rd."  is honored only in the initrd, while the one without prefix is only honored on the host.

	   Table 1. Available breakpoints
	   ┌─────────────────┬───────────────────────────┬───────────────────────────┬─────────────────────────┐
	   │ Breakpoints     │ Description		 │ Can be used in the initrd │ Can be used on the host │
	   ├─────────────────┼───────────────────────────┼───────────────────────────┼─────────────────────────┤
	   │ pre-udev	     │ Before starting to	 │ ✓			     │ ✓		       │
	   │		     │ process kernel uevents,	 │			     │			       │
	   │		     │ i.e., before		 │			     │			       │
	   │		     │ systemd-udevd.service	 │			     │			       │
	   │		     │ starts.			 │			     │			       │
	   ├─────────────────┼───────────────────────────┼───────────────────────────┼─────────────────────────┤
	   │ pre-basic	     │ Before leaving early boot │ ✓			     │ ✓		       │
	   │		     │ and regular services	 │			     │			       │
	   │		     │ start, i.e., before	 │			     │			       │
	   │		     │ basic.target is reached.	 │			     │			       │
	   ├─────────────────┼───────────────────────────┼───────────────────────────┼─────────────────────────┤
	   │ pre-mount	     │ Before the root		 │ ✓			     │ ✗		       │
	   │		     │ filesystem is mounted,	 │			     │			       │
	   │		     │ i.e., before		 │			     │			       │
	   │		     │ sysroot.mount starts.	 │			     │			       │
	   ├─────────────────┼───────────────────────────┼───────────────────────────┼─────────────────────────┤
	   │ pre-switch-root │ Before switching from the │ ✓			     │ ✗		       │
	   │		     │ initrd to the real root.	 │			     │			       │
	   └─────────────────┴───────────────────────────┴───────────────────────────┴─────────────────────────┘

	   Added in version 258.

SYSTEM CREDENTIALS
       systemd.extra-unit.*
	   Credentials prefixed with "systemd.extra-unit."  specify additional units to add to the final system. Note that
	   these additional units are added to both the initrd and the final system.
	   ConditionPathExists=!/etc/initrd-release can be used to make sure the unit is conditioned out in the initrd. Note
	   that this can also be used to mask units, by simply specifying an empty value.

	   Added in version 256.

       systemd.unit-dropin.*
	   Credentials prefixed with "systemd.unit-dropin."  add drop-ins for the corresponding units in the final system.
	   Each credential must be suffixed with the full unit name including the unit extension. Its contents must be a
	   valid unit drop-in file. Optionally, the unit name may be followed with "~", followed by the drop-in name without
	   the ".conf" suffix. If not specified, the name of the generated drop-in will be "50-credential.conf". Note that
	   these additional drop-ins are added to both the initrd and the final system.

	   Added in version 256.

SEE ALSO
       systemd(1), systemctl(1), kernel-command-line(7), systemd.system-credentials(7), bootup(7)

systemd 259.5											  SYSTEMD-DEBUG-GENERATOR(8)