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LFS201 - Chapter 22 Discussion // Questions // Banter - Encrypting Disks

In the section Using an Encrypted Partition a device mapper path is mentioned - although only in passing as a reference to the fs location of the pass-through device created when opening an encrypted disk.

This was my first exposure to the Device Mapper and it's made me wonder if it's a foundational concept that I should already understand or is it something that will be covered in more detail later in the course?

One question I had about it's functionality was that it didn't seem to control/create a mapping for a loopback device after I mounted one.

Comments

  • coopcoop Posts: 717

    The next section in the course is on LVM (logical volume management) which is built on top of device mapper. Because we don't go into the internals of how LVM works we actually don't discuss device mapper. And one doesn't need to know this at all to use LVM. For example, on my system I would have:

    c8:/home/coop/Desktop>l /dev/VG2/
    total 0
    drwxr-xr-x  2 root root  120 Jul  5 07:02 ./
    drwxr-xr-x 22 root root 3620 Jul  5 07:03 ../
    lrwxrwxrwx  1 root root    7 Jul  5 07:02 ISAY -> ../dm-2
    lrwxrwxrwx  1 root root    7 Jul  5 07:02 P -> ../dm-1
    lrwxrwxrwx  1 root root    7 Jul  5 07:02 POLD -> ../dm-0
    

    so that if I directly wanted to refer to the LVM partition I can work with "/dev/VG2/ISAY" instead of "/dev/dm-2"; it is all the same.

    Perhaps we should talk about disk-mapper, but on the other hand the fact that you wondered about this and are looking things up is the kind of behaviour that makes sure you learn more things :)

  • Hi @GRO 108 ,

    Not sure what distro you are using, but this documentation of Device Mapper for RHEL 7 gives very useful information:

    https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/device_mapper

    Regards,
    Luis.

  • GRO 108GRO 108 Posts: 46

    Thanks for the example @coop and the link @luisviveropena

    Guidance like this really helps to make sure that I'm not straying off the path of best practice. It's a wild web out there, who knows what crazy ideas about the device mapper I may come across :sweat_smile:

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