How to fill a device with zeros, without overwriting the bytes that are already zeros? Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) 2019 Community Moderator Election Results Why I closed the “Why is Kali so hard” questionHow to wipe a partition quickly with value zero?Cryptsetup: pre-fill the partition with random datahow to use dd to fill drive with 1'sWhy is dd reading from and writing to the same disk?Is it feasible to fill a ntfs partition/device pre install with zeroess?How large is the img that dd creates?How to overwrite beginning of a device with random bits or zeros?I have killed my HDDIs it necessary to fill a device with zeroes before writing an ISO to it?How to dd a TrueOS installer to USB, on LinuxHow to set the passphrase that different keys are discriminable

How does debian/ubuntu knows a package has a updated version

The logistics of corpse disposal

How do I keep my slimes from escaping their pens?

Do I really need recursive chmod to restrict access to a folder?

Is the Standard Deduction better than Itemized when both are the same amount?

Can I cast Passwall to drop an enemy into a 20-foot pit?

Is it ethical to give a final exam after the professor has quit before teaching the remaining chapters of the course?

Bete Noir -- no dairy

Generate an RGB colour grid

Why did the rest of the Eastern Bloc not invade Yugoslavia?

Why do people hide their license plates in the EU?

String `!23` is replaced with `docker` in command line

Extract all GPU name, model and GPU ram

What does this icon in iOS Stardew Valley mean?

How come Sam didn't become Lord of Horn Hill?

What exactly is a "Meth" in Altered Carbon?

At the end of Thor: Ragnarok why don't the Asgardians turn and head for the Bifrost as per their original plan?

Using audio cues to encourage good posture

When were vectors invented?

Denied boarding although I have proper visa and documentation. To whom should I make a complaint?

Why do we bend a book to keep it straight?

Coloring maths inside a tcolorbox

Why is my conclusion inconsistent with the van't Hoff equation?

Output the ŋarâþ crîþ alphabet song without using (m)any letters



How to fill a device with zeros, without overwriting the bytes that are already zeros?



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
2019 Community Moderator Election Results
Why I closed the “Why is Kali so hard” questionHow to wipe a partition quickly with value zero?Cryptsetup: pre-fill the partition with random datahow to use dd to fill drive with 1'sWhy is dd reading from and writing to the same disk?Is it feasible to fill a ntfs partition/device pre install with zeroess?How large is the img that dd creates?How to overwrite beginning of a device with random bits or zeros?I have killed my HDDIs it necessary to fill a device with zeroes before writing an ISO to it?How to dd a TrueOS installer to USB, on LinuxHow to set the passphrase that different keys are discriminable



.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








5















I have a USB flash drive usb 3, the reading speed is much more than the writing speed.
Let's say that 99% of the flash memory is already full with zeros, and I would like to fill it with zeros until 100%, by overwriting all the memory flash with zeros dd if=/dev/zero of=/dev/FLASH.



This process is going to be long, and it will minimize the life expectancy of the flash drive.



I thought, maybe it would be much quicker to check which areas are non-zero, and overwrite only those non-zertos areas with zeros?



Are there anyways of doing this? If it is interesting, I would need all this for security reasons.










share|improve this question
























  • Does the device have a file system on it? And files? Mainly, though, if this is a one-time affair, then dd if=/dev/zero of=/dev/FLASH would be a heck of a lot faster than writing a program to read the drive one block at a time, comparing it to zeros, and rewriting it if it is.

    – RonJohn
    Sep 16 '18 at 16:55











  • dd if=/dev/zero of=/dev/FLASH is not secure enough for legal/compliance purposes, if that is a concern readmoar on secure erase.

    – mikst
    Sep 16 '18 at 17:22











  • who do you need to be secure from? what sort of budget does the attacker have? writing zeros to a flash drive may only hide the data.

    – Jasen
    Sep 16 '18 at 20:45












  • @RonJohn imagine that there is no file system. I want to be 100% that there are only zeros on the flash drive, regardless of whether there is a file system there or not.

    – Slok
    Sep 17 '18 at 14:51











  • @Jasen filling the flash drive with zeros I consider sufficient in my circumstances.

    – Slok
    Sep 17 '18 at 14:51

















5















I have a USB flash drive usb 3, the reading speed is much more than the writing speed.
Let's say that 99% of the flash memory is already full with zeros, and I would like to fill it with zeros until 100%, by overwriting all the memory flash with zeros dd if=/dev/zero of=/dev/FLASH.



This process is going to be long, and it will minimize the life expectancy of the flash drive.



I thought, maybe it would be much quicker to check which areas are non-zero, and overwrite only those non-zertos areas with zeros?



Are there anyways of doing this? If it is interesting, I would need all this for security reasons.










share|improve this question
























  • Does the device have a file system on it? And files? Mainly, though, if this is a one-time affair, then dd if=/dev/zero of=/dev/FLASH would be a heck of a lot faster than writing a program to read the drive one block at a time, comparing it to zeros, and rewriting it if it is.

    – RonJohn
    Sep 16 '18 at 16:55











  • dd if=/dev/zero of=/dev/FLASH is not secure enough for legal/compliance purposes, if that is a concern readmoar on secure erase.

    – mikst
    Sep 16 '18 at 17:22











  • who do you need to be secure from? what sort of budget does the attacker have? writing zeros to a flash drive may only hide the data.

    – Jasen
    Sep 16 '18 at 20:45












  • @RonJohn imagine that there is no file system. I want to be 100% that there are only zeros on the flash drive, regardless of whether there is a file system there or not.

    – Slok
    Sep 17 '18 at 14:51











  • @Jasen filling the flash drive with zeros I consider sufficient in my circumstances.

    – Slok
    Sep 17 '18 at 14:51













5












5








5








I have a USB flash drive usb 3, the reading speed is much more than the writing speed.
Let's say that 99% of the flash memory is already full with zeros, and I would like to fill it with zeros until 100%, by overwriting all the memory flash with zeros dd if=/dev/zero of=/dev/FLASH.



This process is going to be long, and it will minimize the life expectancy of the flash drive.



I thought, maybe it would be much quicker to check which areas are non-zero, and overwrite only those non-zertos areas with zeros?



Are there anyways of doing this? If it is interesting, I would need all this for security reasons.










share|improve this question
















I have a USB flash drive usb 3, the reading speed is much more than the writing speed.
Let's say that 99% of the flash memory is already full with zeros, and I would like to fill it with zeros until 100%, by overwriting all the memory flash with zeros dd if=/dev/zero of=/dev/FLASH.



This process is going to be long, and it will minimize the life expectancy of the flash drive.



I thought, maybe it would be much quicker to check which areas are non-zero, and overwrite only those non-zertos areas with zeros?



Are there anyways of doing this? If it is interesting, I would need all this for security reasons.







security dd






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Sep 16 '18 at 16:04







user88036

















asked Sep 16 '18 at 15:30









SlokSlok

282




282












  • Does the device have a file system on it? And files? Mainly, though, if this is a one-time affair, then dd if=/dev/zero of=/dev/FLASH would be a heck of a lot faster than writing a program to read the drive one block at a time, comparing it to zeros, and rewriting it if it is.

    – RonJohn
    Sep 16 '18 at 16:55











  • dd if=/dev/zero of=/dev/FLASH is not secure enough for legal/compliance purposes, if that is a concern readmoar on secure erase.

    – mikst
    Sep 16 '18 at 17:22











  • who do you need to be secure from? what sort of budget does the attacker have? writing zeros to a flash drive may only hide the data.

    – Jasen
    Sep 16 '18 at 20:45












  • @RonJohn imagine that there is no file system. I want to be 100% that there are only zeros on the flash drive, regardless of whether there is a file system there or not.

    – Slok
    Sep 17 '18 at 14:51











  • @Jasen filling the flash drive with zeros I consider sufficient in my circumstances.

    – Slok
    Sep 17 '18 at 14:51

















  • Does the device have a file system on it? And files? Mainly, though, if this is a one-time affair, then dd if=/dev/zero of=/dev/FLASH would be a heck of a lot faster than writing a program to read the drive one block at a time, comparing it to zeros, and rewriting it if it is.

    – RonJohn
    Sep 16 '18 at 16:55











  • dd if=/dev/zero of=/dev/FLASH is not secure enough for legal/compliance purposes, if that is a concern readmoar on secure erase.

    – mikst
    Sep 16 '18 at 17:22











  • who do you need to be secure from? what sort of budget does the attacker have? writing zeros to a flash drive may only hide the data.

    – Jasen
    Sep 16 '18 at 20:45












  • @RonJohn imagine that there is no file system. I want to be 100% that there are only zeros on the flash drive, regardless of whether there is a file system there or not.

    – Slok
    Sep 17 '18 at 14:51











  • @Jasen filling the flash drive with zeros I consider sufficient in my circumstances.

    – Slok
    Sep 17 '18 at 14:51
















Does the device have a file system on it? And files? Mainly, though, if this is a one-time affair, then dd if=/dev/zero of=/dev/FLASH would be a heck of a lot faster than writing a program to read the drive one block at a time, comparing it to zeros, and rewriting it if it is.

– RonJohn
Sep 16 '18 at 16:55





Does the device have a file system on it? And files? Mainly, though, if this is a one-time affair, then dd if=/dev/zero of=/dev/FLASH would be a heck of a lot faster than writing a program to read the drive one block at a time, comparing it to zeros, and rewriting it if it is.

– RonJohn
Sep 16 '18 at 16:55













dd if=/dev/zero of=/dev/FLASH is not secure enough for legal/compliance purposes, if that is a concern readmoar on secure erase.

– mikst
Sep 16 '18 at 17:22





dd if=/dev/zero of=/dev/FLASH is not secure enough for legal/compliance purposes, if that is a concern readmoar on secure erase.

– mikst
Sep 16 '18 at 17:22













who do you need to be secure from? what sort of budget does the attacker have? writing zeros to a flash drive may only hide the data.

– Jasen
Sep 16 '18 at 20:45






who do you need to be secure from? what sort of budget does the attacker have? writing zeros to a flash drive may only hide the data.

– Jasen
Sep 16 '18 at 20:45














@RonJohn imagine that there is no file system. I want to be 100% that there are only zeros on the flash drive, regardless of whether there is a file system there or not.

– Slok
Sep 17 '18 at 14:51





@RonJohn imagine that there is no file system. I want to be 100% that there are only zeros on the flash drive, regardless of whether there is a file system there or not.

– Slok
Sep 17 '18 at 14:51













@Jasen filling the flash drive with zeros I consider sufficient in my circumstances.

– Slok
Sep 17 '18 at 14:51





@Jasen filling the flash drive with zeros I consider sufficient in my circumstances.

– Slok
Sep 17 '18 at 14:51










1 Answer
1






active

oldest

votes


















4














Security reasons aside, let's do it. We can (ab)use GNU ddrescue.



To detect sectors of zeros --generate-mode is useful.




When ddrescue is invoked with the --generate-mode option it operates in "generate mode", which is different from the default "rescue mode". That is, if you use the --generate-mode option, ddrescue does not rescue anything. It only tries to generate a mapfile for later use.



[…]



ddrescue can in some cases generate an approximate mapfile, from infile and the (partial) copy in outfile, that is almost as good as an exact mapfile. It makes this by simply assuming that sectors containing all zeros were not rescued.



[…]



ddrescue --generate-mode infile outfile mapfile



(source)



Let's pretend your device is outfile from previous ddrescue run. We cannot use it as infile (because ddrescue refuses to work when infile and outfile are the same file), we need a dummy one, /dev/zero will do. We should know the physical sector size of your device and use it with -b option. This command may help:



lsblk -o NAME,PHY-SeC /dev/FLASH


Here I assume it's 512.



ddrescue -b 512 --generate-mode /dev/zero /dev/FLASH flash.map


Now flash.map describes every sector either as non-tried (?) or as finished (+), depending on whether it was full of zeros or not. The next step is to fill non-zero sectors with zeros; --fill-mode is perfect for this job:




When ddrescue is invoked with the --fill-mode option it operates in "fill mode", which is different from the default "rescue mode". That is, if you use the --fill-mode option, ddrescue does not rescue anything. It only fills with data read from infile the blocks of outfile whose status character from mapfile coincides with one of the type characters specified as argument to the --fill-mode option.




(source)



We must use the same -b value as with --generate-mode, additionally --force to overwrite the output device. This is the command:



ddrescue -b 512 --force --fill-mode=+ /dev/zero /dev/FLASH flash.map


This time /dev/zero is not just a dummy argument, it's the actual source of data (zeros) written to the device.



After ddrescue finishes, invoke sync. Now /dev/FLASH is filled with zeros.






share|improve this answer

























    Your Answer








    StackExchange.ready(function()
    var channelOptions =
    tags: "".split(" "),
    id: "106"
    ;
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function()
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled)
    StackExchange.using("snippets", function()
    createEditor();
    );

    else
    createEditor();

    );

    function createEditor()
    StackExchange.prepareEditor(
    heartbeatType: 'answer',
    autoActivateHeartbeat: false,
    convertImagesToLinks: false,
    noModals: true,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: null,
    bindNavPrevention: true,
    postfix: "",
    imageUploader:
    brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
    contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
    allowUrls: true
    ,
    onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    );



    );













    draft saved

    draft discarded


















    StackExchange.ready(
    function ()
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f469399%2fhow-to-fill-a-device-with-zeros-without-overwriting-the-bytes-that-are-already%23new-answer', 'question_page');

    );

    Post as a guest















    Required, but never shown

























    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    4














    Security reasons aside, let's do it. We can (ab)use GNU ddrescue.



    To detect sectors of zeros --generate-mode is useful.




    When ddrescue is invoked with the --generate-mode option it operates in "generate mode", which is different from the default "rescue mode". That is, if you use the --generate-mode option, ddrescue does not rescue anything. It only tries to generate a mapfile for later use.



    […]



    ddrescue can in some cases generate an approximate mapfile, from infile and the (partial) copy in outfile, that is almost as good as an exact mapfile. It makes this by simply assuming that sectors containing all zeros were not rescued.



    […]



    ddrescue --generate-mode infile outfile mapfile



    (source)



    Let's pretend your device is outfile from previous ddrescue run. We cannot use it as infile (because ddrescue refuses to work when infile and outfile are the same file), we need a dummy one, /dev/zero will do. We should know the physical sector size of your device and use it with -b option. This command may help:



    lsblk -o NAME,PHY-SeC /dev/FLASH


    Here I assume it's 512.



    ddrescue -b 512 --generate-mode /dev/zero /dev/FLASH flash.map


    Now flash.map describes every sector either as non-tried (?) or as finished (+), depending on whether it was full of zeros or not. The next step is to fill non-zero sectors with zeros; --fill-mode is perfect for this job:




    When ddrescue is invoked with the --fill-mode option it operates in "fill mode", which is different from the default "rescue mode". That is, if you use the --fill-mode option, ddrescue does not rescue anything. It only fills with data read from infile the blocks of outfile whose status character from mapfile coincides with one of the type characters specified as argument to the --fill-mode option.




    (source)



    We must use the same -b value as with --generate-mode, additionally --force to overwrite the output device. This is the command:



    ddrescue -b 512 --force --fill-mode=+ /dev/zero /dev/FLASH flash.map


    This time /dev/zero is not just a dummy argument, it's the actual source of data (zeros) written to the device.



    After ddrescue finishes, invoke sync. Now /dev/FLASH is filled with zeros.






    share|improve this answer





























      4














      Security reasons aside, let's do it. We can (ab)use GNU ddrescue.



      To detect sectors of zeros --generate-mode is useful.




      When ddrescue is invoked with the --generate-mode option it operates in "generate mode", which is different from the default "rescue mode". That is, if you use the --generate-mode option, ddrescue does not rescue anything. It only tries to generate a mapfile for later use.



      […]



      ddrescue can in some cases generate an approximate mapfile, from infile and the (partial) copy in outfile, that is almost as good as an exact mapfile. It makes this by simply assuming that sectors containing all zeros were not rescued.



      […]



      ddrescue --generate-mode infile outfile mapfile



      (source)



      Let's pretend your device is outfile from previous ddrescue run. We cannot use it as infile (because ddrescue refuses to work when infile and outfile are the same file), we need a dummy one, /dev/zero will do. We should know the physical sector size of your device and use it with -b option. This command may help:



      lsblk -o NAME,PHY-SeC /dev/FLASH


      Here I assume it's 512.



      ddrescue -b 512 --generate-mode /dev/zero /dev/FLASH flash.map


      Now flash.map describes every sector either as non-tried (?) or as finished (+), depending on whether it was full of zeros or not. The next step is to fill non-zero sectors with zeros; --fill-mode is perfect for this job:




      When ddrescue is invoked with the --fill-mode option it operates in "fill mode", which is different from the default "rescue mode". That is, if you use the --fill-mode option, ddrescue does not rescue anything. It only fills with data read from infile the blocks of outfile whose status character from mapfile coincides with one of the type characters specified as argument to the --fill-mode option.




      (source)



      We must use the same -b value as with --generate-mode, additionally --force to overwrite the output device. This is the command:



      ddrescue -b 512 --force --fill-mode=+ /dev/zero /dev/FLASH flash.map


      This time /dev/zero is not just a dummy argument, it's the actual source of data (zeros) written to the device.



      After ddrescue finishes, invoke sync. Now /dev/FLASH is filled with zeros.






      share|improve this answer



























        4












        4








        4







        Security reasons aside, let's do it. We can (ab)use GNU ddrescue.



        To detect sectors of zeros --generate-mode is useful.




        When ddrescue is invoked with the --generate-mode option it operates in "generate mode", which is different from the default "rescue mode". That is, if you use the --generate-mode option, ddrescue does not rescue anything. It only tries to generate a mapfile for later use.



        […]



        ddrescue can in some cases generate an approximate mapfile, from infile and the (partial) copy in outfile, that is almost as good as an exact mapfile. It makes this by simply assuming that sectors containing all zeros were not rescued.



        […]



        ddrescue --generate-mode infile outfile mapfile



        (source)



        Let's pretend your device is outfile from previous ddrescue run. We cannot use it as infile (because ddrescue refuses to work when infile and outfile are the same file), we need a dummy one, /dev/zero will do. We should know the physical sector size of your device and use it with -b option. This command may help:



        lsblk -o NAME,PHY-SeC /dev/FLASH


        Here I assume it's 512.



        ddrescue -b 512 --generate-mode /dev/zero /dev/FLASH flash.map


        Now flash.map describes every sector either as non-tried (?) or as finished (+), depending on whether it was full of zeros or not. The next step is to fill non-zero sectors with zeros; --fill-mode is perfect for this job:




        When ddrescue is invoked with the --fill-mode option it operates in "fill mode", which is different from the default "rescue mode". That is, if you use the --fill-mode option, ddrescue does not rescue anything. It only fills with data read from infile the blocks of outfile whose status character from mapfile coincides with one of the type characters specified as argument to the --fill-mode option.




        (source)



        We must use the same -b value as with --generate-mode, additionally --force to overwrite the output device. This is the command:



        ddrescue -b 512 --force --fill-mode=+ /dev/zero /dev/FLASH flash.map


        This time /dev/zero is not just a dummy argument, it's the actual source of data (zeros) written to the device.



        After ddrescue finishes, invoke sync. Now /dev/FLASH is filled with zeros.






        share|improve this answer















        Security reasons aside, let's do it. We can (ab)use GNU ddrescue.



        To detect sectors of zeros --generate-mode is useful.




        When ddrescue is invoked with the --generate-mode option it operates in "generate mode", which is different from the default "rescue mode". That is, if you use the --generate-mode option, ddrescue does not rescue anything. It only tries to generate a mapfile for later use.



        […]



        ddrescue can in some cases generate an approximate mapfile, from infile and the (partial) copy in outfile, that is almost as good as an exact mapfile. It makes this by simply assuming that sectors containing all zeros were not rescued.



        […]



        ddrescue --generate-mode infile outfile mapfile



        (source)



        Let's pretend your device is outfile from previous ddrescue run. We cannot use it as infile (because ddrescue refuses to work when infile and outfile are the same file), we need a dummy one, /dev/zero will do. We should know the physical sector size of your device and use it with -b option. This command may help:



        lsblk -o NAME,PHY-SeC /dev/FLASH


        Here I assume it's 512.



        ddrescue -b 512 --generate-mode /dev/zero /dev/FLASH flash.map


        Now flash.map describes every sector either as non-tried (?) or as finished (+), depending on whether it was full of zeros or not. The next step is to fill non-zero sectors with zeros; --fill-mode is perfect for this job:




        When ddrescue is invoked with the --fill-mode option it operates in "fill mode", which is different from the default "rescue mode". That is, if you use the --fill-mode option, ddrescue does not rescue anything. It only fills with data read from infile the blocks of outfile whose status character from mapfile coincides with one of the type characters specified as argument to the --fill-mode option.




        (source)



        We must use the same -b value as with --generate-mode, additionally --force to overwrite the output device. This is the command:



        ddrescue -b 512 --force --fill-mode=+ /dev/zero /dev/FLASH flash.map


        This time /dev/zero is not just a dummy argument, it's the actual source of data (zeros) written to the device.



        After ddrescue finishes, invoke sync. Now /dev/FLASH is filled with zeros.







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Dec 19 '18 at 7:38

























        answered Oct 29 '18 at 23:29









        Kamil MaciorowskiKamil Maciorowski

        1,75711030




        1,75711030



























            draft saved

            draft discarded
















































            Thanks for contributing an answer to Unix & Linux Stack Exchange!


            • Please be sure to answer the question. Provide details and share your research!

            But avoid


            • Asking for help, clarification, or responding to other answers.

            • Making statements based on opinion; back them up with references or personal experience.

            To learn more, see our tips on writing great answers.




            draft saved


            draft discarded














            StackExchange.ready(
            function ()
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f469399%2fhow-to-fill-a-device-with-zeros-without-overwriting-the-bytes-that-are-already%23new-answer', 'question_page');

            );

            Post as a guest















            Required, but never shown





















































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown

































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown







            -dd, security

            Popular posts from this blog

            Frič See also Navigation menuinternal link

            Identify plant with long narrow paired leaves and reddish stems Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) Announcing the arrival of Valued Associate #679: Cesar Manara Unicorn Meta Zoo #1: Why another podcast?What is this plant with long sharp leaves? Is it a weed?What is this 3ft high, stalky plant, with mid sized narrow leaves?What is this young shrub with opposite ovate, crenate leaves and reddish stems?What is this plant with large broad serrated leaves?Identify this upright branching weed with long leaves and reddish stemsPlease help me identify this bulbous plant with long, broad leaves and white flowersWhat is this small annual with narrow gray/green leaves and rust colored daisy-type flowers?What is this chilli plant?Does anyone know what type of chilli plant this is?Help identify this plant

            fontconfig warning: “/etc/fonts/fonts.conf”, line 100: unknown “element blank” The 2019 Stack Overflow Developer Survey Results Are In“tar: unrecognized option --warning” during 'apt-get install'How to fix Fontconfig errorHow do I figure out which font file is chosen for a system generic font alias?Why are some apt-get-installed fonts being ignored by fc-list, xfontsel, etc?Reload settings in /etc/fonts/conf.dTaking 30 seconds longer to boot after upgrade from jessie to stretchHow to match multiple font names with a single <match> element?Adding a custom font to fontconfigRemoving fonts from fontconfig <match> resultsBroken fonts after upgrading Firefox ESR to latest Firefox