This section describes environment variables that affect how
mdadm operates.
MDADM_NO_MDMON
Setting this value to 1 will prevent mdadm from
automatically launching mdmon. This variable is intended
primarily for debugging mdadm/mdmon.
MDADM_NO_UDEV
Normally, mdadm does not create any device nodes in /dev,
but leaves that task to udev. If udev appears not to be
configured, or if this environment variable is set to '1',
the mdadm will create and devices that are needed.
MDADM_NO_SYSTEMCTL
If mdadm detects that systemd is in use it will normally
request systemd to start various background tasks
(particularly mdmon) rather than forking and running them
in the background. This can be suppressed by setting
MDADM_NO_SYSTEMCTL=1.
IMSM_NO_PLATFORM
A key value of IMSM metadata is that it allows
interoperability with boot ROMs on Intel platforms, and
with other major operating systems. Consequently, mdadm
will only allow an IMSM array to be created or modified if
detects that it is running on an Intel platform which
supports IMSM, and supports the particular configuration
of IMSM that is being requested (some functionality
requires newer OROM support).
These checks can be suppressed by setting
IMSM_NO_PLATFORM=1 in the environment. This can be useful
for testing or for disaster recovery. You should be aware
that interoperability may be compromised by setting this
value.
MDADM_GROW_ALLOW_OLD
If an array is stopped while it is performing a reshape
and that reshape was making use of a backup file, then
when the array is re-assembled mdadm will sometimes
complain that the backup file is too old. If this happens
and you are certain it is the right backup file, you can
over-ride this check by setting MDADM_GROW_ALLOW_OLD=1 in
the environment.
MDADM_CONF_AUTO
Any string given in this variable is added to the start of
the AUTO line in the config file, or treated as the whole
AUTO line if none is given. It can be used to disable
certain metadata types when mdadm is called from a boot
script. For example
export MDADM_CONF_AUTO='-ddf -imsm'
will make sure that mdadm does not automatically assemble
any DDF or IMSM arrays that are found. This can be useful
on systems configured to manage such arrays with dmraid.
