U-boot environment variables in linux - Revision history

Peterll: Use correct application name in comment, fix typo in comment

2012-08-31T15:38:59Z

Use correct application name in comment, fix typo in comment

Markv: Added OpenWrt menuconfig location

2010-11-07T14:08:25Z

Added OpenWrt menuconfig location

JulienBoibessot: /* Setting and verifying an environment variable */

2010-02-11T09:48:41Z

‎Setting and verifying an environment variable

JulienBoibessot at 09:36, 11 February 2010

2010-02-11T09:36:00Z

JulienBoibessot: Correct minor typos + (try to) make it independant of OE + add infos for Buildroot

2010-02-11T09:27:38Z

Correct minor typos + (try to) make it independant of OE + add infos for Buildroot

RobertK: +cats

2008-10-27T12:14:38Z

+cats

RobertK at 12:13, 27 October 2008

2008-10-27T12:13:04Z

New page

U-boot makes use of environment variable which can be read and set from the u-boot command line with printenv and setenv. It can be helpful to read and set these variables from linux as well. The u-boot distribution has sources for these commands, named fw_printenv and fw_setenv, but the Angstrom OE distribution does not build the tools automatically. I'm a novice at OE and bitbake, so here are the instructions for building and installing the tools manually. Theses instructions assume that you have already buillt the angstrom distribution for the beagle board. Substitute directories and compiler locations to match your environment.

#cd to the source for u-boot in the OE tree. For me, it is at "../oe/tmp/work/beagleboard-angstrom-linux-gnueabi/u-boot-git-r18.1/git"
#manually build fw_printenv with make: "make env ARCH=arm CROSS_COMPILE= /usr/local/angstrom/arm/bin/arm-angstrom-linux-gnuabi-"
#if the compile succeeded, you should have fw_printenv in the u-boot directory tools/env. Copy fw_printenv to /sbin on the root filesystem of your beagle board.
#the fw_printenv binary also contains the code for fw_setenv. the functions of fw_setenv are run when the program is invoked with the name "fw_setenv". this is most easily accomplished by creating a symbolic link from fw_printenv to fw_setenv, as in "ln -sf /sbin/fw_printenv /sbin/fw_setenv"
#the last and most important step is creating the config file for the utilities. the file name is fw_env.config and it lives in /etc.
to create this file, you need to know information about where u-boot stores its env variables. Specifically, you need the mtd device name, the device offset, the env size and the flash sector size. I found most of what I needed by looking in the file /proc/mtd. here is my fw_env.config file:

# Configuration file for fw_(printenv/saveenv) utility.
# Up to two entries are valid, in this case the redundand
# environment sector is assumed present.
# MTD device name Device offset Env. size Flash sector size
/dev/mtd2 0x0000 0x20000 0x20000

== Usage ==
=== Printing all the environment variables===

# fw_printenv
bootdelay=1
baudrate=115200
ipaddr=192.168.0.2
serverip=192.168.0.1
netmask=255.255.255.0
bootfile="uImage"
filesize=B81A24
bootcmd=nand read 80200000 280000 400000;bootm 80200000
bootargs=console=ttyS2,115200n8 console=tty0 root=/dev/mtdblock4 rw rootfstyp=jffs2 nohz=off
stdin=serial
stdout=serial
stderr=serial

=== Printing a single environment variable ===
# fw_printenv stdin
stdin=serial

=== Setting and verifying an environment variable ===
WARNING! If the fw_env.config does not point to u-boots env section in flash, running fw_setenv could corrupt your flash. Make sure that fw_printenv works properly and does not return a message about "bad CRC" before running fw_setenv.

# fw_setenv mytestvariable abcdefg
# fw_printenv mytestvariable
mytestenv=abcdefg

Care must be taken when changing env variables as a typo could easily render your boot unbootable. Most problems can be fixed by connecting to the serial console and using u-boots command line to fix bad variable.

← Older revision		Revision as of 14:08, 7 November 2010
Line 21:		Line 21:

	Tools will be installed in ''/usr/sbin/'' of your target's rootfs.		Tools will be installed in ''/usr/sbin/'' of your target's rootfs.
		+
		+	===OpenWrt===
		+	Like Buildroot, OpenWrt can build these tools too but you will find them in a different location in the menu:
		+	Utilities --->
		+	[*] uboot-envtools
		+
		+	Tools will also be installed in ''/usr/sbin/''.

	===All distribs===		===All distribs===

@@ Line 54: / Line 54: @@
 === Setting and verifying an environment variable ===
-WARNING!  If the ''fw_env.config'' does not point to U-Boot's env section in Flash, running ''fw_setenv'' could corrupt your flash.  Make sure that ''fw_printenv'' works properly and does not return a message about "bad CRC" before running ''fw_setenv''.
+WARNING!  If the ''fw_env.config'' does not point to U-Boot's env section in Flash, running ''fw_setenv'' could corrupt your Flash.  Make sure that ''fw_printenv'' works properly and does not return a message about "bad CRC" before running ''fw_setenv''.
    # fw_setenv mytestvariable abcdefg
@@ Line 61: / Line 61: @@
-Care must be taken when changing env variables as a typo could easily render your boot unbootable. Most problems can be fixed by connecting to the serial console and using U-Boot's command line to fix bad variable.
+Care must be taken when changing env variables as a typo could easily render your system unbootable. Most problems can be fixed by connecting to the serial console and using U-Boot's command line to fix bad variable.

← Older revision		Revision as of 09:36, 11 February 2010
Line 1:		Line 1:
		+	[[Category: U-Boot]]
	[[Category: Linux]]		[[Category: Linux]]
	[[Category: OMAP]]		[[Category: OMAP]]

← Older revision		Revision as of 12:14, 27 October 2008
Line 1:		Line 1:
		+	[[Category: Linux]]
		+	[[Category: OMAP]]
	U-boot makes use of environment variable which can be read and set from the u-boot command line with printenv and setenv. It can be helpful to read and set these variables from linux as well. The u-boot distribution has sources for these commands, named fw_printenv and fw_setenv, but the Angstrom OE distribution does not build the tools automatically. I'm a novice at OE and bitbake, so here are the instructions for building and installing the tools manually. Theses instructions assume that you have already buillt the angstrom distribution for the beagle board. Substitute directories and compiler locations to match your environment.		U-boot makes use of environment variable which can be read and set from the u-boot command line with printenv and setenv. It can be helpful to read and set these variables from linux as well. The u-boot distribution has sources for these commands, named fw_printenv and fw_setenv, but the Angstrom OE distribution does not build the tools automatically. I'm a novice at OE and bitbake, so here are the instructions for building and installing the tools manually. Theses instructions assume that you have already buillt the angstrom distribution for the beagle board. Substitute directories and compiler locations to match your environment.

@@ Line 33: / Line 33: @@
 To create this file, you need to know information about where U-Boot stores its env variables.  Specifically, you need the mtd device name, the device offset, the env size and the flash sector size.  I found most of what I needed by looking in the file ''/proc/mtd''. Here is my ''fw_env.config'' file:
-    # Configuration file for fw_(printenv/saveenv) utility.
+    # Configuration file for fw_(printenv/setenv) utility.
-    # Up to two entries are valid, in this case the redundand
+    # Up to two entries are valid, in this case the redundant
     # environment sector is assumed present.
     # MTD device name       Device offset   Env. size       Flash sector size

@@ Line 1: / Line 1: @@
 [[Category: Linux]]
 [[Category: OMAP]]
-U-boot makes use of environment variable which can be read and set from the u-boot command line with printenv and setenv.  It can be helpful to read and set these variables from linux as well.  The u-boot distribution has sources for these commands, named fw_printenv and fw_setenv, but the Angstrom OE distribution does not build the tools automatically.  I'm a novice at OE and bitbake, so here are the instructions for building and installing the tools manually.  Theses instructions assume that you have already buillt the angstrom distribution for the beagle board.  Substitute directories and compiler locations to match your environment.
+U-Boot makes use of environment variables which can be read and set from the U-Boot command line with ''printenv'' and ''setenv''.  It can be helpful to read and set these variables from Linux as well.  The U-Boot distribution has sources for these commands, named ''fw_printenv'' and ''fw_setenv''.
-#cd to the source for u-boot in the OE tree.  For me, it is at "../oe/tmp/work/beagleboard-angstrom-linux-gnueabi/u-boot-git-r18.1/git"
+== Installation ==
 #manually build fw_printenv with make:  "make env ARCH=arm CROSS_COMPILE= /usr/local/angstrom/arm/bin/arm-angstrom-linux-gnuabi-"
-#if the compile succeeded, you should have fw_printenv in the u-boot directory tools/env.  Copy fw_printenv to /sbin on the root filesystem of your beagle board.
+#if the compile succeeded, you should have fw_printenv in the U-Boot directory tools/env.  Copy fw_printenv to /sbin on the root filesystem of your beagle board.
 #the fw_printenv binary also contains the code for fw_setenv.  the functions of fw_setenv are run when the program is invoked with the name "fw_setenv".  this is most easily accomplished by creating a symbolic link from fw_printenv to fw_setenv, as in "ln -sf /sbin/fw_printenv /sbin/fw_setenv"
-#the last and most important step is creating the config file for the utilities.  the file name is fw_env.config and it lives in /etc.
-to create this file, you need to know information about where u-boot stores its env variables.  Specifically, you need the mtd device name, the device offset, the env size and the flash sector size.  I found most of what I needed by looking in the file /proc/mtd.  here is my fw_env.config file:
+===Buildroot===
     # Configuration file for fw_(printenv/saveenv) utility.
@@ Line 38: / Line 53: @@
 === Setting and verifying an environment variable ===
-WARNING!  If the fw_env.config does not point to u-boots env section in flash, running fw_setenv could corrupt your flash.  Make sure that fw_printenv works properly and does not return a message about "bad CRC" before running fw_setenv.
+WARNING!  If the ''fw_env.config'' does not point to U-Boot's env section in Flash, running ''fw_setenv'' could corrupt your flash.  Make sure that ''fw_printenv'' works properly and does not return a message about "bad CRC" before running ''fw_setenv''.
    # fw_setenv mytestvariable abcdefg
@@ Line 45: / Line 60: @@
-Care must be taken when changing env variables as a typo could easily render your boot unbootable. Most problems can be fixed by connecting to the serial console and using u-boots command line to fix bad variable.
+Care must be taken when changing env variables as a typo could easily render your boot unbootable. Most problems can be fixed by connecting to the serial console and using U-Boot's command line to fix bad variable.