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27. Devices and udev - Device Nodes - ¿Filesystem?

I don't understand why in Section 27. "Devices and udev", Page "Device Nodes", the illustrations shows a block "filesystem" between the blocks "block driver" and "block node"?

Looking at the "ls -l /dev" output before, the block node "sda" has the same major as its partition block nodes "sda1" and "sda2", and I believe this is completely independent of whatever filesystem-or-not the partition holds. Of course, in order to mount it, there should be a filesystem; but the pure "block node" of a partition should already show up in the VFS (under /etc) regardless of formatting (otherwise, how to run mkfs on it?).

Best Answer

  • coop
    coop Posts: 879
    Answer ✓

    Yes indeed, the order should be vfs<->fs<->node<->hw ; i.e., file system and node should be swapped. I think an redraw of the graphic at some point introduced the error. We will fix.

    All scsi disks have major number 8, with varying minor numbers. In an MBR system you have 16 for each physical drive, for example on my system which currently has 4 disks:

    c8:/>ls -l /dev/sd*
    brw-rw---- 1 root disk 8,  0 Feb  7 07:13 /dev/sda
    brw-rw---- 1 root disk 8,  1 Feb  7 07:13 /dev/sda1
    brw-rw---- 1 root disk 8,  2 Feb  7 07:13 /dev/sda2
    brw-rw---- 1 root disk 8, 16 Feb  7 07:13 /dev/sdb
    brw-rw---- 1 root disk 8, 17 Feb  7 07:13 /dev/sdb1
    brw-rw---- 1 root disk 8, 18 Feb  7 07:13 /dev/sdb2
    brw-rw---- 1 root disk 8, 32 Feb  7 07:13 /dev/sdc
    brw-rw---- 1 root disk 8, 33 Feb  7 07:13 /dev/sdc1
    brw-rw---- 1 root disk 8, 34 Feb  7 07:13 /dev/sdc2
    brw-rw---- 1 root disk 8, 48 Feb  7 07:13 /dev/sdd
    brw-rw---- 1 root disk 8, 49 Feb  7 07:13 /dev/sdd1
    brw-rw---- 1 root disk 8, 51 Feb  7 07:13 /dev/sdd3
    brw-rw---- 1 root disk 8, 53 Feb  7 07:13 /dev/sdd5
    brw-rw---- 1 root disk 8, 54 Feb  7 07:13 /dev/sdd6
    

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