When flashing a Linux System on a SD card using the script mk_mx28_sd on a Ubuntu 12.04 host, one needs to modify it so partitions are created correctly. Just follow these steps on the console:
$ cd $SDK/L2.6.35_10.12.01_SDK_scripts
$ cat > first_partition_sector.patch << EOF
diff -Naur a/mk_mx28_sd b/mk_mx28_sd
--- a/mk_mx28_sd 2010-10-06 09:47:42.000000000 -0500
+++ b/mk_mx28_sd 2012-11-30 13:38:34.508199154 -0600
@@ -178,7 +178,7 @@
n
p
1
-1
+2048
+32M
t
b
EOF
$ patch -p1 < first_partition_sector.patch
then, you can run the mk_mx28_sd command again with the device as parameter
$ cd $LIB
$ export PATH=$PATH:$SDK/L2.6.35_10.12.01_SDK_scripts
$ mk_mx28_sd /dev/$SDX