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.
