Does Grub have an OS or drivers of its own?

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I've been reading the Grub intro from Dedoimedo and despite being an excellent guide it raised some more questions:



Does Grub rely on any OS in its implementation? I know it's possible to configure it to load Windows, Linux, FreeBSD, etc. So I'm guessing it doesn't rely on any kernel (even a special-made minimal Linux kernel) right? In that case, how can it show a graphical interface, access whatever media to load the kernel, etc. all in "20-30 KB of binary"?



Update: one follow up question: what are all those vmlinuz files in the /boot dir? Are those in any way related to Grub?










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    up vote
    0
    down vote

    favorite












    I've been reading the Grub intro from Dedoimedo and despite being an excellent guide it raised some more questions:



    Does Grub rely on any OS in its implementation? I know it's possible to configure it to load Windows, Linux, FreeBSD, etc. So I'm guessing it doesn't rely on any kernel (even a special-made minimal Linux kernel) right? In that case, how can it show a graphical interface, access whatever media to load the kernel, etc. all in "20-30 KB of binary"?



    Update: one follow up question: what are all those vmlinuz files in the /boot dir? Are those in any way related to Grub?










    share|improve this question

























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I've been reading the Grub intro from Dedoimedo and despite being an excellent guide it raised some more questions:



      Does Grub rely on any OS in its implementation? I know it's possible to configure it to load Windows, Linux, FreeBSD, etc. So I'm guessing it doesn't rely on any kernel (even a special-made minimal Linux kernel) right? In that case, how can it show a graphical interface, access whatever media to load the kernel, etc. all in "20-30 KB of binary"?



      Update: one follow up question: what are all those vmlinuz files in the /boot dir? Are those in any way related to Grub?










      share|improve this question















      I've been reading the Grub intro from Dedoimedo and despite being an excellent guide it raised some more questions:



      Does Grub rely on any OS in its implementation? I know it's possible to configure it to load Windows, Linux, FreeBSD, etc. So I'm guessing it doesn't rely on any kernel (even a special-made minimal Linux kernel) right? In that case, how can it show a graphical interface, access whatever media to load the kernel, etc. all in "20-30 KB of binary"?



      Update: one follow up question: what are all those vmlinuz files in the /boot dir? Are those in any way related to Grub?







      grub






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      edited 1 min ago









      Rui F Ribeiro

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      37.3k1374118










      asked Mar 31 '17 at 8:14









      AlexStack

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          1 Answer
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          2
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          accepted










          Right, Grub is standalone and implements all its own drivers. It does take rather more than “20-30 KB of binary” to do this though; my /boot/grub/i386-pc directory contains 2.4 MiB’s worth of modules (which is where all the Grub features are implemented).



          The vmlinuz files in /boot are the various Linux kernels you have installed. Grub doesn’t need them, they’re what Grub loads to boot Linux (along with an initramfs).






          share|improve this answer






















          • Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
            – AlexStack
            Mar 31 '17 at 9:31











          • Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
            – Philippos
            Mar 31 '17 at 11:54










          • I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
            – Stephen Kitt
            Mar 31 '17 at 11:59










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          1 Answer
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          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









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          oldest

          votes






          active

          oldest

          votes








          up vote
          2
          down vote



          accepted










          Right, Grub is standalone and implements all its own drivers. It does take rather more than “20-30 KB of binary” to do this though; my /boot/grub/i386-pc directory contains 2.4 MiB’s worth of modules (which is where all the Grub features are implemented).



          The vmlinuz files in /boot are the various Linux kernels you have installed. Grub doesn’t need them, they’re what Grub loads to boot Linux (along with an initramfs).






          share|improve this answer






















          • Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
            – AlexStack
            Mar 31 '17 at 9:31











          • Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
            – Philippos
            Mar 31 '17 at 11:54










          • I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
            – Stephen Kitt
            Mar 31 '17 at 11:59














          up vote
          2
          down vote



          accepted










          Right, Grub is standalone and implements all its own drivers. It does take rather more than “20-30 KB of binary” to do this though; my /boot/grub/i386-pc directory contains 2.4 MiB’s worth of modules (which is where all the Grub features are implemented).



          The vmlinuz files in /boot are the various Linux kernels you have installed. Grub doesn’t need them, they’re what Grub loads to boot Linux (along with an initramfs).






          share|improve this answer






















          • Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
            – AlexStack
            Mar 31 '17 at 9:31











          • Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
            – Philippos
            Mar 31 '17 at 11:54










          • I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
            – Stephen Kitt
            Mar 31 '17 at 11:59












          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          Right, Grub is standalone and implements all its own drivers. It does take rather more than “20-30 KB of binary” to do this though; my /boot/grub/i386-pc directory contains 2.4 MiB’s worth of modules (which is where all the Grub features are implemented).



          The vmlinuz files in /boot are the various Linux kernels you have installed. Grub doesn’t need them, they’re what Grub loads to boot Linux (along with an initramfs).






          share|improve this answer














          Right, Grub is standalone and implements all its own drivers. It does take rather more than “20-30 KB of binary” to do this though; my /boot/grub/i386-pc directory contains 2.4 MiB’s worth of modules (which is where all the Grub features are implemented).



          The vmlinuz files in /boot are the various Linux kernels you have installed. Grub doesn’t need them, they’re what Grub loads to boot Linux (along with an initramfs).







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Mar 31 '17 at 9:47

























          answered Mar 31 '17 at 8:18









          Stephen Kitt

          152k23338406




          152k23338406











          • Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
            – AlexStack
            Mar 31 '17 at 9:31











          • Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
            – Philippos
            Mar 31 '17 at 11:54










          • I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
            – Stephen Kitt
            Mar 31 '17 at 11:59
















          • Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
            – AlexStack
            Mar 31 '17 at 9:31











          • Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
            – Philippos
            Mar 31 '17 at 11:54










          • I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
            – Stephen Kitt
            Mar 31 '17 at 11:59















          Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
          – AlexStack
          Mar 31 '17 at 9:31





          Good to know. I'm curious what are the vmlinuz images in /boot? Added it as an "Update" question to the original question so feel free to edit the answer if you see fit :)
          – AlexStack
          Mar 31 '17 at 9:31













          Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
          – Philippos
          Mar 31 '17 at 11:54




          Really all drivers? I don't know much about Grub, but I've been writing a bootloader for an embedded device as fast and compact uboot replacement. Of course I had to write some drivers, but not all, as there was some bootROM code executed by the CPU first, doing things like initializing the memory where my bootloader lives. I can imagine that Grub also relies on those lowest-level drivers, implemented in the BIOS or UEFI or whatever may be up to date in today's PCs.
          – Philippos
          Mar 31 '17 at 11:54












          I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
          – Stephen Kitt
          Mar 31 '17 at 11:59




          I meant in opposition to using Linux drivers (or something else). The Grub drivers do use the BIOS in some cases; for example biosdisk.c uses the BIOS to access disks, but there’s also pata.c to directly access PATA disks (allowing Grub to access drives which the BIOS can’t — which was useful on many older systems).
          – Stephen Kitt
          Mar 31 '17 at 11:59

















           

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