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NAME | SYNOPSIS | DESCRIPTION | KERNEL COMMAND LINE | SYSTEM CREDENTIALS | SEE ALSO | COLOPHON |
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SYSTEMD-...GENERATOR(8) systemd-debug-generator SYSTEMD-...GENERATOR(8)
systemd-debug-generator - Generator for enabling a runtime debug
shell and masking specific units at boot
/usr/lib/systemd/system-generators/systemd-debug-generator
systemd-debug-generator is a generator that provides some
debugging functionality.
systemd-debug-generator implements systemd.generator(7).
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.
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.
systemd(1), systemctl(1), kernel-command-line(7),
systemd.system-credentials(7), bootup(7)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 SYSTEMD-...GENERATOR(8)
Pages that refer to this page: kernel-command-line(7), systemd.directives(7), systemd.generator(7), systemd.index(7), systemd.system-credentials(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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