Fix guard command environment for FFDC

Signed-off-by: Anusha Dathatri <adathatr@in.ibm.com>
Change-Id: I533996a13364b3fff3e7afcf83c13e78b48fd065
diff --git a/lib/openbmc_ffdc_list.py b/lib/openbmc_ffdc_list.py
index 80d048e..5401bfc 100755
--- a/lib/openbmc_ffdc_list.py
+++ b/lib/openbmc_ffdc_list.py
@@ -69,7 +69,8 @@
         + ' org.open_power.OCC.Status OccActive) done > /tmp/OCC_state.txt 2>&1',
         'bmcweb_persistent_data.json': 'cat /home/root/bmcweb_persistent_data.json'
         + ' > /tmp/bmcweb_persistent_data.json',
-        'GUARD_list.txt': 'guard -l > /tmp/GUARD_list.txt 2>&1',
+        'GUARD_list.txt': 'export PDBG_DTB=/var/lib/phosphor-software-manager/pnor/rw/DEVTREE;'
+        + 'guard -l > /tmp/GUARD_list.txt 2>&1',
         'fan_control_dump.json': 'fanctl dump; cat /tmp/fan_control_dump.json'
         + ' /tmp/fan_control_dump.json 2>&1',
         'DEVTREE': 'cp /var/lib/phosphor-software-manager/pnor/rw/DEVTREE'