From 5033f52497a444831696f178ba6ee77722a4533d Mon Sep 17 00:00:00 2001
From: Michael Prokop <mika@grml.org>
Date: Thu, 13 Apr 2017 23:47:47 +0200
Subject: [PATCH 1/1] Support --rw-blockdev option for usage with
 read-only/forensic like devices

If the system is running in a read-only mode for devices and
setting devices to read-only when they appear (e.g. partition
table scans) then we need to explictely set read-write mode
on the involved devices (e.g. /dev/sdx + /dev/sdx2 if /dev/sd2
is the target partition).

Be aware that you might have to use the --skip-bootflag option
as well then, because this option triggers parted code which
is behaving bad with read-only devices.
---
 grml2usb | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/grml2usb b/grml2usb
index b188539..05067e4 100755
--- a/grml2usb
+++ b/grml2usb
@@ -103,6 +103,8 @@ parser.add_option("--quiet", dest="quiet", action="store_true",
                   help="do not output anything but just errors on console")
 parser.add_option("--remove-bootoption", dest="removeoption", action="append",
                   help="regex for removing existing bootoptions")
+parser.add_option("--rw-blockdev", dest="rwblockdev", action="store_true",
+                  help="enforce read-write mode on involved block devices")
 parser.add_option("--skip-addons", dest="skipaddons", action="store_true",
                   help="do not install /boot/addons/ files")
 parser.add_option("--skip-bootflag", dest="skipbootflag", action="store_true",
@@ -252,6 +254,17 @@ def get_function_name(obj):
     return obj.__module__ + '.' + obj.__name__
 
 
+def set_rw(device):
+    if not options.rwblockdev:
+        return
+
+    logging.debug("executing: blockdev --setrw %s", device)
+    proc = subprocess.Popen(["blockdev", "--setrw", device])
+    proc.wait()
+    if proc.returncode != 0:
+        raise Exception("error executing blockdev on %s" % device)
+
+
 def execute(f, *exec_arguments):
     """Wrapper for executing a command. Either really executes
     the command (default) or when using --dry-run commandline option
@@ -498,6 +511,9 @@ def install_grub(device):
             else:
                 grub_device = device
 
+            set_rw(device)
+            set_rw(grub_device)
+
             logging.info("Installing grub as bootloader")
             for opt in ["", "--force"]:
                 logging.debug("grub-install --recheck %s --no-floppy --root-directory=%s %s",
@@ -537,6 +553,8 @@ def install_syslinux(device):
         logging.info("Would install syslinux as bootloader on %s", device)
         return 0
 
+    set_rw(device)
+
     # syslinux -d boot/isolinux /dev/sdb1
     logging.info("Installing syslinux as bootloader")
     logging.debug("syslinux -d boot/syslinux %s", device)
@@ -647,6 +665,8 @@ def install_mbr(mbrtemplate, device, partition, ismirbsdmbr=True):
     tmpf.file.write(mbrcode)
     tmpf.file.close()
 
+    set_rw(device)
+
     logging.debug("executing: dd if='%s' of='%s' bs=512 count=1 conv=notrunc", tmpf.name, device)
     proc = subprocess.Popen(["dd", "if=%s" % tmpf.name, "of=%s" % device, "bs=512", "count=1",
                              "conv=notrunc"], stderr=file(os.devnull, "r+"))
@@ -659,6 +679,8 @@ def install_mbr(mbrtemplate, device, partition, ismirbsdmbr=True):
     proc = subprocess.Popen(["sync"])
     proc.wait()
 
+    set_rw(device)
+
 
 def is_writeable(device):
     """Check if the device is writeable for the current user
@@ -693,6 +715,8 @@ def mount(source, target, mount_options):
         logging.debug("Source %s is not a device, therefore not mounting.", source)
         return 0
 
+    set_rw(source)
+
     logging.debug("mount %s %s %s", mount_options, source, target)
     proc = subprocess.Popen(["mount"] + list(mount_options) + [source, target])
     proc.wait()
-- 
2.1.4