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Create bootable USB on Linux or OS x command line

Linux Systems Guides
  • To create a bootable image on a USB ‘stick’ aka ‘thumb drive’ ‘flash drive’ in linux or OS x we use the ‘dd’ command.

    In this case, we’ll write the latest (as of this writeup) Debian Image , which happens to be 8.5.0 amd64

    I generally try to use the torrent, taking in consideration the server/ bandwidth costs involved with free and open software.

    Download the image you wish to use. Many times the image you use, will depend on what size USB device you have available. Or obviously what you wish to accomplish.

    In this case I’m using a USB card reader, with a 32 GB Micro SD card

    You’ll need to know what USB device name to use. An easy way to view what devices are currently mounted would be to use:


    There are many options, or flags if you need them. From the man pages:

           -a, --all
                  Also list empty devices.  (By default they are skipped.)
           -b, --bytes
                  Print the SIZE column in bytes rather than in a human-readable
           -D, --discard
                  Print information about the discarding capabilities (TRIM,
                  UNMAP) for each device.
           -d, --nodeps
                  Do not print holder devices or slaves.  For example, lsblk
                  --nodeps /dev/sda prints information about the sda device
           -e, --exclude list
                  Exclude the devices specified by the comma-separated list of
                  major device numbers.  Note that RAM disks (major=1) are
                  excluded by default.  The filter is applied to the top-level
                  devices only.
           -f, --fs
                  Output info about filesystems.  This option is equivalent to
                  -o NAME,FSTYPE,LABEL,UUID,MOUNTPOINT.  The authoritative
                  information about filesystems and raids is provided by the
                  blkid(8) command.
           -h, --help
                  Display help text and exit.
           -I, --include list
                  Include devices specified by the comma-separated list of major
                  device numbers.  The filter is applied to the top-level
                  devices only.
           -i, --ascii
                  Use ASCII characters for tree formatting.
           -J, --json
                  Use JSON output format.
           -l, --list
                  Produce output in the form of a list.
           -m, --perms
                  Output info about device owner, group and mode.  This option
                  is equivalent to -o NAME,SIZE,OWNER,GROUP,MODE.
           -n, --noheadings
                  Do not print a header line.
           -o, --output list
                  Specify which output columns to print.  Use --help to get a
                  list of all supported columns.
                  The default list of columns may be extended if list is
                  specified in the format +list (e.g. lsblk -o +UUID).
           -O, --output-all
                  Output all available columns.
           -P, --pairs
                  Produce output in the form of key="value" pairs.  All
                  potentially unsafe characters are hex-escaped (\x<code>).
           -p, --paths
                  Print full device paths.
           -r, --raw
                  Produce output in raw format.  All potentially unsafe
                  characters are hex-escaped (\x<code>) in the NAME, KNAME,
                  LABEL, PARTLABEL and MOUNTPOINT columns.
           -S, --scsi
                  Output info about SCSI devices only.  All partitions, slaves
                  and holder devices are ignored.
           -s, --inverse
                  Print dependencies in inverse order.
           -t, --topology
                  Output info about block-device topology.  This option is
                  equivalent to -o NAME,ALIGNMENT,MIN-IO,OPT-IO,PHY-SEC,LOG-
           -V, --version
                  Display version information and exit.
           -x, --sort column
                  Sort output lines by column.

    In this case, the system spits out the following disks:

    NAME                        MAJ:MIN RM   SIZE RO TYPE   MOUNTPOINT
    sda                           8:0    0 465.8G  0 disk   
    └─isw_ccheigfjba_Volume0    254:0    0 931.5G  0 dmraid 
      ├─isw_ccheigfjba_Volume01 254:1    0 893.8G  0 dmraid /
      └─isw_ccheigfjba_Volume05 254:3    0  37.7G  0 dmraid 
    sdb                           8:16   0 465.8G  0 disk   
    └─isw_ccheigfjba_Volume0    254:0    0 931.5G  0 dmraid 
      ├─isw_ccheigfjba_Volume01 254:1    0 893.8G  0 dmraid /
      └─isw_ccheigfjba_Volume05 254:3    0  37.7G  0 dmraid 
    sdc                           8:32   1   1.9G  0 disk   
    ├─sdc1                        8:33   1   925M  0 part   
    └─sdc2                        8:34   1  86.1M  0 part

    We can see three devices on this system shown by ‘sda’ ‘sdb’ and ‘sdc’, where sda and sdb are each 500GB drives in a raid array. And sdc is the USB device we’ll use.

    These naming conventions will not always be the case, depending on operating system. sdc will not always be your USB device.

    It’s very important to insure you are writing to the correct disk, as well as not trying to write to a partition on the desired target disk. As in:

    sdc                           8:32   1   1.9G  0 disk   
    ├─sdc1                        8:33   1   925M  0 part   
    └─sdc2                        8:34   1  86.1M  0 part

    Where in the above example, we see ‘sdc’ as the disk, and two partitions called ‘sdc1’ and ‘sdc2’

    You could go about formatting the disk at this point, however the commands we will use in this example will simply ignore and over write any and all partitions, erasing any and all data on the target device. Effectively destroying anything currently on the device.

    Once the image, or ISO is downloaded to your local machine, navigate to the directory which your downloads reside (generally the users ‘Download’ directory).

    Of course it is not required to move to the directory where the image is, at that point you’ll need to type the path, I say go to the Downloads directory for easy of use and simplify the command.

    In this case the image name is: debian-8.5.0-amd64-DVD-1.iso

    The disk is: sdc

    So the command to write the image ‘debian-8.5.0-amd64-DVD-1.iso’ To disk ‘sdc’

    You may need to unmount the device before this will work

    umount /dev/sdc 

    You would then run the following command:

    sudo dd if=debian-8.5.0-amd64-DVD-1.iso of=/dev/sdc bs=1M

    You’ll of course be requested to type in your sudo password, or at least you should not be running as root to begin with.

    The write will commence, and depending on the machine capabilities and the size of the image being written, will dictate the speed at which the procedure takes.

    There is no progress bar with this command, so sit back, or get on with another task. This could take quite some time.

    Once the image is written to the USB device and completed, the output will look something to this effect:

    3808+0 records in
    3808+0 records out
    3992977408 bytes (4.0 GB) copied, 288.986 s, 13.8 MB/s

    We can see here, that the USB device is now partitioned and the ISO is available.

    sdc                           8:32   1  29.7G  0 disk   
    ├─sdc1                        8:33   1   3.7G  0 part   /media/rick/Debian 8.5.0 amd64 1
    └─sdc2                        8:34   1   416K  0 part

    There is quite a lot of discussion as to which block size to write, or as seen in the above command ‘bs=1M’ , I have used 5M, however much faster, I’ve had instances where {something @ somewhere} went sour and left me with a useless image. Possibly due to incorrect writes, that is however for another discussion.

FreeBSD Notes
  • rickR

    Locate hard drive and get information

    ls -l /sys/block | grep sd.


    lrwxrwxrwx 1 root root 0 Jun 22 06:28 sda -> ../devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda lrwxrwxrwx 1 root root 0 Jun 22 06:28 sdb -> ../devices/pci0000:00/0000:00:1f.2/ata2/host1/target1:0:0/1:0:0:0/block/sdb lrwxrwxrwx 1 root root 0 Jun 22 06:28 sdc -> ../devices/pci0000:00/0000:00:1f.2/ata3/host2/target2:0:0/2:0:0:0/block/sdc lrwxrwxrwx 1 root root 0 Jun 22 06:28 sdd -> ../devices/pci0000:00/0000:00:1f.2/ata4/host3/target3:0:0/3:0:0:0/block/sdd

    Or for a more detailed view

    strace -e trace=open lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS sda 8:0 0 3.6T 0 disk ├─data--2-data--2_tmeta 252:3 0 15.9G 0 lvm │ └─data--2-data--2-tpool 252:9 0 3.6T 0 lvm │ ├─data--2-data--2 252:10 0 3.6T 1 lvm │ ├─data--2-vm--101--disk--0 252:11 0 8G 0 lvm │ ├─data--2-vm--103--disk--0 252:12 0 32G 0 lvm │ ├─data--2-vm--107--disk--0 252:13 0 500G 0 lvm │ └─data--2-vm--108--disk--0 252:20 0 100G 0 lvm └─data--2-data--2_tdata 252:6 0 3.6T 0 lvm └─data--2-data--2-tpool 252:9 0 3.6T 0 lvm ├─data--2-data--2 252:10 0 3.6T 1 lvm ├─data--2-vm--101--disk--0 252:11 0 8G 0 lvm ├─data--2-vm--103--disk--0 252:12 0 32G 0 lvm ├─data--2-vm--107--disk--0 252:13 0 500G 0 lvm └─data--2-vm--108--disk--0 252:20 0 100G 0 lvm sdb 8:16 0 698.6G 0 disk └─sdb1 8:17 0 698.6G 0 part /mnt/pve/backups sdc 8:32 0 3.6T 0 disk ├─vm--data-vm--data_tmeta 252:4 0 15.9G 0 lvm │ └─vm--data-vm--data-tpool 252:14 0 3.6T 0 lvm │ ├─vm--data-vm--data 252:15 0 3.6T 1 lvm │ ├─vm--data-vm--100--disk--0 252:16 0 270G 0 lvm │ ├─vm--data-vm--102--disk--0 252:17 0 100G 0 lvm │ ├─vm--data-vm--104--disk--0 252:18 0 25G 0 lvm │ └─vm--data-vm--106--disk--0 252:19 0 32G 0 lvm └─vm--data-vm--data_tdata 252:7 0 3.6T 0 lvm └─vm--data-vm--data-tpool 252:14 0 3.6T 0 lvm ├─vm--data-vm--data 252:15 0 3.6T 1 lvm ├─vm--data-vm--100--disk--0 252:16 0 270G 0 lvm ├─vm--data-vm--102--disk--0 252:17 0 100G 0 lvm ├─vm--data-vm--104--disk--0 252:18 0 25G 0 lvm └─vm--data-vm--106--disk--0 252:19 0 32G 0 lvm sdd 8:48 0 931.5G 0 disk ├─sdd1 8:49 0 1007K 0 part ├─sdd2 8:50 0 1G 0 part └─sdd3 8:51 0 930.5G 0 part ├─pve-swap 252:0 0 8G 0 lvm [SWAP] ├─pve-root 252:1 0 96G 0 lvm / ├─pve-data_tmeta 252:2 0 8.1G 0 lvm │ └─pve-data 252:8 0 794.3G 0 lvm └─pve-data_tdata 252:5 0 794.3G 0 lvm └─pve-data 252:8 0 794.3G 0 lvm +++ exited with 0 +++ cat /proc/partitions major minor #blocks name 8 0 3907018584 sda 8 16 732574584 sdb 8 17 732572672 sdb1 8 32 3907018584 sdc 8 48 976762584 sdd 8 49 1007 sdd1 8 50 1048576 sdd2 8 51 975712967 sdd3 252 0 8388608 dm-0 252 1 100663296 dm-1 252 2 8495104 dm-2 252 3 16650240 dm-3 252 4 16650240 dm-4 252 6 3873329152 dm-6 252 5 832888832 dm-5 252 7 3873329152 dm-7 252 8 832888832 dm-8 252 9 3873329152 dm-9 252 10 3873329152 dm-10 252 11 8388608 dm-11 252 12 33554432 dm-12 252 13 524288000 dm-13 252 14 3873329152 dm-14 252 15 3873329152 dm-15 252 16 283115520 dm-16 252 17 104857600 dm-17 252 18 26214400 dm-18 252 19 33554432 dm-19 252 20 104857600 dm-20

    Locate drive by serial and model information

    hdparm -i /dev/sda /dev/sda: Model=WDC WD4000FYYZ-05UL1B0, FwRev=00.0NS05, SerialNo=WD-WCC132262513 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=0 BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=off CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=7814037168 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 AdvancedPM=yes: unknown setting WriteCache=disabled Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7 * signifies the current active mode
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  • rickR

    Screen recording can use webm as their format, it can be more simple to use a gif to embed into a website or forum, than adding scripts to host different video format.

    In this case I grabbed a screen record of the progress for writing zeros to a hard drive with dd

    Use ffmpeg to convert webm to gif:

    First create a pallet:

    Move into the directory which the webm is located, or type in the path

    Where ‘dd.webm’ is the screen recording

    ffmpeg -y -i dd.webm -vf palettegen palette.png



    Then convert the webm to gif:

    ffmpeg -y -i dd.webm -i palette.png -filter_complex paletteuse -r 10 dd.gif


    This is what I ended up with, looks like any image of any alien on the interwebz, as if shot through a potato, some tweaking of the command is in my future. None the less.


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  • rickR

    Write zeros to all sectors

    Use the command ‘lsblk’ to find the drive you wish to erase

    I’m using ‘dd’ to erase things

    In this case I’m torching sdb

    Only use status=progress if you care it’s not necessary

    dd if=/dev/zero of=/dev/sdb bs=12M status=progress


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  • rickR

    Remove old kernel images that are cluttering the system


    Most of these errors are due to low or not enough space left in the root partition.

    If you are using a Debian flavor:

    sudo apt-get autoremove --purge


    Inform grub whenever an old kernel is removed:

    update grub


    Remove the un-used kernel config files:

    These will be the files pre cursed as ‘rc’ where installed kernels use ‘ii’

    … As well as files no longer used or required due to dependencies

    This command will detect, print, and remove left over cruft from previously installed packages or scripts, that have been removed or updated.

    sudo dpkg --purge $(dpkg -l | awk '/^rc/{print $2}')


    You can re-run the following to view the installed kernel(s):

    dpkg --list | grep linux-image


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  • rickR

    To list all files in current directory including dot files (hidden files or directories), as well as print permissions :

    ls -la
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