xorriso-dd-target evaluates block devices of the Linux kernel whether they are suitable targets for a
disk image file and optionally copies the image file to one of them.
It is specialized on the device names of the Linuxkernel and uses the capabilities of util-linux program
lsblk. Therefore it refuses to run on non-Linux kernels.
The main purpose of xorriso-dd-target is to inspect the device files of disk-like storage media and to
judge whether they look like removable devices with disposable content.
If a single plausible candidate is detected, then the program is willing to copy a disk image file onto
it. This will overwrite or make inaccessible the previous partition table and all previous data content
of the target device.
Superuserpower is often needed for filesystem type identification, for possible unmounting, and for
possible image writing. Option -with_sudo offers a way to gain this power only for those tasks and to
run the program elsewise with a normal user's power.
If a particular disk image file is intended as copy source, then its path should be given by option
-image_file, so that its size can be used as decision criterion.
Following are use case descriptions with examples:
- List plain device names
- List all devices with reasoning
- Evaluate particular given devices
- Detect intended device by plugging
- Write image to an advised device
- Show commands for writing to a not advised device
Listplaindevicenames:
The most simple and most boring use case is a program run without device names and without options
-list_all, -plug_test, -DO_WRITE, -dummy_force. It prints on standard output (stdout) only the names of
advisable devices without "/dev/" prefix. One name per line and without any reasoning text.
The possible sudo password prompt, the message line about sudo, and the empty line after it do not go to
stdout.
Example:
$ xorriso-dd-target -with_sudo
Testing sudo to possibly get password prompting done now:
[sudo] password for thomas:
sudo /bin/lsblk seems ok.
sde
Listalldeviceswithreasoning:
For the more curious user, there is option -list_all which prints the evaluation of each disk-like device
that is listed by program lsblk. Optical drives, floppy disks, RAM block devices, loop devices are
excluded, though.
Each device is shown by one line of the form
name : advice : reasoning : info
name is the device name without "/dev/" prefix.
advice is either "YES" or "NO". "YES" indicates that the device appears to be pluggable disk-like, not
used as system disk or sincere data storage, and - if tested - of sufficient or plausible size.
reasoning is a blank separated list of words with either suffix '+' for an inviting device property or
'-' for a prohibitive property. Normally a single '-' reason disqualifies the device from being
advisable. Only if option -look_for_iso is given, a reason "has_XYZ-" can be overridden by the presence
of an ISO 9660 filesystem on the device.
info is composed from VENDOR and MODEL as told by lsblk.
Option -list_long causes with each line an additional listing of the information provided by lsblk which
led to the shown reasons.
Example:
$ xorriso-dd-target -with_sudo -list_all
...
sda : NO : not_usb- has_vfat+ has_ext4- : ATA Samsung SSD 850
sdb : NO : not_usb- has_swap- has_ext4- : ATA WDC WD20EFRX-68A
sdc : YES : usb+ has_iso9660+ has_vfat+ : Intenso Ultra Line
sdd : NO : usb+ has_iso9660+ has_vfat+ has_ext2- : SanDisk Cruzer
Evaluateparticulargivendevices:
If devicenames are given instead of option -list_all, then only these devices are inspected. Their
result gets listed without the ": info" part, unless option -with_vendor_model is given.
Device names must not begin by '-' and must be single words composed of the characters [A-za-z0-9_/-].
They should not contain '/'. E.g. 'sdc' is valid, '/dev/sdc' is not valid.
If one of the given device names gets not advised, the exit value is 1.
It makes few sense to give device names which are not listed by -list_all.
Examples:
$ xorriso-dd-target -with_sudo sdc
...
sdc : YES : usb+ has_iso9660+ has_vfat+
$ xorriso-dd-target -with_sudo -with_vendor_model sdc
...
sdc : YES : usb+ has_iso9660+ has_vfat+ : Intenso Ultra Line
$ xorriso-dd-target sdc
sdc : NO : usb+ no_fs_while_not_su-
Detectintendeddevicebyplugging:
Option -plug_test triggers an interactive method to unambiguously determine the intended target device
candidate. It consists of 2 or 3 steps.
Step1 is to have the intended storage device unplugged and to confirm this by pressing the Enter key at
the program's prompt. The program will then assess the list of not wanted devices.
Step2 is to plugin the intended storage device and to confirm this by pressing the Enter key a second
time. The program will wait up to 10 seconds for a disk-like storage device which is not in the list of
not wanted devices. The user may wait with key pressing until the device blinking looks like it is
ready.
Only if a single new device is found, the program will go on as if a single device name was given. Option
-list_all and any device names given as arguments will be ignored.
Step3 happens only if options -DO_WRITE or -dummy_force are given. The program asks for a final input
of the word 'yes' before real or simulated writing begins.
Example:
$ xorriso-dd-target -with_sudo -plug_test
...
Caused by option -plug_test: Attempt to find the desired device by watching it appear after being plugged
in.
Step 1:
Please make sure that the desired target device is plugged _out_ now.
If it is currently plugged in, make sure to unmount all its filesystems
and then unplug it.
Press the Enter key when ready.
Found and noted as _not_ desired: sda sdb sdc
Step 2:
Please plug in the desired target device and then press the Enter key.
Waiting up to 10 seconds for a new device to be listed ... found: sdd
Now waiting 5 seconds to let it settle .........
Found and noted as desired device: sdd
sdd : NO : usb+ has_iso9660+ has_vfat+ has_ext2- : SanDisk Cruzer
Writeimagetoanadviseddevice:
Only if option -DO_WRITE is given and -list_all is not, and if exactly one advisable device is listed, it
really gets overwritten by the file content of the given -image_file. In this case the exit value is zero
if writing succeeded, non-zero else.
Option -dummy prevents this kind of real action and rather shows the planned umount and dd commands on
stdout.
Example:
$ xorriso-dd-target -with_sudo -plug_test -DO_WRITE \
-image_file debian-live-10.0.0-amd64-xfce.iso
... sudo messages and above plug test steps 1 and 2 ...
sde : YES : usb+ has_iso9660+ has_vfat+
Step 3:
Last chance to abort. Enter the word 'yes' to start REAL WRITING.
yes
Looking for mount points of sde:
/dev/sde1 on /mnt/iso type iso9660 (ro,relatime)
/dev/sde2 on /mnt/fat type vfat (rw,...,errors=remount-ro)
Unmounted: /dev/sde1
Unmounted: /dev/sde2
Performing:
sudo /bin/dd if=/dev/zero of=/dev/'sde' bs=512 seek='245759999'
count=1 status=none
sudo /bin/dd if='debian-live-10.0.0-amd64-xfce.iso' of=/dev/'sde'
bs=1M status=progress oflag=dsync ; sync
... dd messages ...
The first dd run shall erase a possible GPT backup header. It is performed only if the local program
"expr" can deal with the byte size of the device.
Showcommandsforwritingtoanotadviseddevice:
There should be no way to convince xorriso-dd-target of writing to a target device which it does not deem
advisable. Please report any set of arguments that can be misused for that.
The outmost complicity to potentially unwise actions is offered by option -dummy_force. If given together
with a single device name or with option -plug_test it will act like -dummy -DO_WRITE with this device,
even if it looks not advisable. I.e. it will show the shell commands which the program does not dare to
perform.
Example:
$ xorriso-dd-target -with_sudo -list_long -dummy_force sdd \
-image_file debian-live-10.0.0-amd64-xfce.iso
...
sdd : NO : usb+ has_iso9660+ has_vfat+ has_ext2-
NAME SIZE FSTYPE TRAN LABEL
sdd 3.8G iso9660 usb d-live 9.5.0 xf i386
|-sdd1 1.9G iso9660 d-live 9.5.0 xf i386
|-sdd2 320K vfat
`-sdd3 512M ext2
Overriding any advice because of -dummy_force
Looking for mount points of sdd:
/dev/sdd1 on /mnt/iso type iso9660 (ro,relatime)
/dev/sdd2 on /mnt/fat type vfat (rw,...,errors=remount-ro)
/dev/sdd3 on /mnt/ext type ext2 (rw,relatime)
AGAINST THE ADVICE BY THIS PROGRAM, a daring user could do:
sudo /bin/umount /dev/sdd1
sudo /bin/umount /dev/sdd2
sudo /bin/umount /dev/sdd3
sudo /bin/dd if=/dev/zero of=/dev/'sdd' bs=512 seek='7864318'
count=1 status=none
sudo /bin/dd if='debian-live-10.0.0-amd64-xfce.iso' of=/dev/sdd
bs=1M status=progress oflag=dsync ; sync
BE SMART. BE CAUTIOUS. BEWARE.
AlphabeticalListofpositiveandnegativereasons:
As stated with use case "List all devices", reasons are words with either suffix '+' for an inviting
device property or '-' for a prohibitive property.
Normally a single '-' reason disqualifies the device from being advisable.
has_XYZ-
A filesystem of type XYZ is detected on base device or partition and is spoiling the impression of a
device with disposable content.
has_iso9660+
An ISO 9660 filesystem is detected.
has_vfat+
A FAT (MS-DOS-like) filesystem is detected.
look_for_iso++
Option -look_for_iso is given and an ISO 9660 filesystem is detected. This reason overrides any
"has_XYZ-" reason.
looks_like_cd_drive-
A given device name looks like the name of an optical drive: sr[0-9]*. Use program xorrecord for this
kind of devices.
looks_like_disk_partition-
A given device name looks like the name of a partition. Expected are names of base devices, like "sde",
not of their partitions, like "sde1".
looks_like_floppy-
A given device name looks like the name of a floppy disk drive: fd[0-9]*.
looks_like_loopdev-
A given device name looks like the name of a loop device: loop[0-9]*.
looks_like_ramdev-
A given device name looks like the name of a RAM block device: zram[0-9]*.
lsblk_no_size-
A size test is given by -max_size, -min_size, or -image_file but the size of the device cannot be
inquired by lsblk. This is supposed to happen only with given inappropriate device names.
mmcblk+
The device name looks like a directly connected memory card.
name_with_slash-
A given device name contains '/' characters.
no_bus_info-
The device is not a memory card and lsblk reports nothing about the way how it is connected to the
computer.
no_fs_while_not_su-
No filesystem is reported by lsblk and the program does not believe to have run it with superuser powers.
There is the risk that lsblk silently failed to detect existing filesystems.
no_iso9660-
Option -look_for_iso is given but no ISO 9660 filesystem is detected.
not_usb-
The device is not a memory card and lsblk reports that it is connected by something other than USB.
size_too_large-
Option -max_size is given with a size smaller than the size of the device.
size_too_small-
Option -min_size or -image_file is given with size or file size larger than the size of the device.
usb+
The device is reported by lsblk to be connected via USB.
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