Artesyn ATCA-9405 Installation and Use (May 2014) - Manual (Page 76)

Service Processor
ATCA-9405 Installation and Use (6806800M71G) 76
The above listing basically describes the order of precedence, that is a variable stored in the
NVRAM can potentially be overridden, modified, or deleted by a variable of the same name
stored in the IPMI boot parameter storage, and later on by dynamic variables declared during
the boot process or by the user from the shell prompt.
Although the saveenv command stores the complete set of variables currently being used
into the NVRAM, the actual setting of these variables might not become valid because they are
overridden by the other entities.
Note that the U-Boot does not synchronize the NVRAM storage and the IPMI boot parameter
storage by itself.
If the NVRAMs CRC is invalid, the NVRAM is initialized with the blade's default values
immediately after detecting the bad CRC (before reading additional values from the IPMC).
4.5.2 Passing Parameter Set to the Operating System
An operating system making use of environment variables should only rely on the RAM copy of
the parameter set.
U-Boot passes its current parameters via the firmware device tree. It generates a node /u-
boot-env
, containing a node for each environment variable. This is done by the bootm
command as the final step before executing the OS image. Under Linux, these parameters
appear under the directory /proc/dev-tree/u-boot-env.
4.5.3 Dynamic Variables Set During the Boot Phase
This section lists the variables that are set during the boot phase.
Table 4-4 Dynamic Variables Set During the Boot Phase
Variable Name Description
boottime The time (UNIX time) when the blade has started. If this variable is set
to "-1" then the RTC does not run at startup
physical_slot The physical slot number where the blade is mounted
logical_slot The logical slot number where the blade is mounted
bootbank The physical boot bank number from which the blade has started (0 or
1)