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 │ Can be used on │
	   │		    │			    │ the initrd     │ 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 258					    SYSTEMD-DEBUG-GENERATOR(8)