Bootloader (U-Boot) • 189
Environment Variables
WAGO-I/O-SYSTEM 750
Linux Fieldbus Coupler
9.5 Environment Variables
A list of all environment variables set can be viewed using
> printenv.
An environment variable can contain values, further environment variables or
U-Boot commands. In the latter case, the environment variable works similar
to a macro which processes the commands one after the other.
The relevant environment variables for the Linux fieldbus coupler boot
process are:
• ipmode
Defines the type of IP configuration. Possible values are bootp, dhcp, a
static IP in the format xxx.xxx.xxx.xxx or a completely static
configuration in the format
<FBK-IP>:<ServerIP>:<GW-IP>:<Netmask>:<Hostname>:<Device>
10.1.1.8:10.1.2:1:10.1.1.254:255.255.255.0:lfbk:eth0
• bootargs
Contains further parameters for the kernel, for example the root file system
(root=/dev/mtdblock3)
• bootcmd
Contains a macro that creates a kernel command line from ipmode and
bootargs and starts the kernel. This macro is called automatically 3
seconds after starting the Linux fieldbus coupler (stored in the bootdelay
variable).
• bootA/bootB
Macros that, depending on the selector switch position of the Linux
fieldbus coupler, are copied to bootcmd when U-Boot is started.
•
bootdelay
The time the system waits for the abort password to arrrive
•
ethaddr
MAC address of the Linux fieldbus coupler
To Next Page
Loading...
