Hi,
On Tue, Oct 1, 2013 at 9:27 AM, Raphael Bauduin <[email protected]> wrote:
>
> How can I determine which is the first free nbd device?
>
By free do you mean not connected?
> Currently I have 2 ways to check if an device is connected: the first is
> calling file on the device and check if it is empty or not. The second is
> call lsblk and see if the device is in the list.
>
Neither of these distinguishes between connected and non-connected...
>
> Rather than looping over all nbd devices until I find one free to use, I
> wondered if there's a way to immediately get the first free nbd device.
>
Not directly, that I know of, but there are two ways to determine which
nbds are connected or not:
/proc/partitions lists only active nbds:
debian-i386~$ cat /proc/partitions
major minor #blocks name
7 1 409600 loop1
7 5 2560000 loop5
8 0 16777216 sda
8 1 16043008 sda1
8 2 1 sda2
8 5 731136 sda5
11 0 1048575 sr0
9 1 409588 md1
43 5 2560000 nbd5
Also, the sysfs pid file is only present when the nbd is connected (i.e.,
an nbd-client is running):
debian-i386~$ cat /sys/block/nbd5/pid
18172
debian-i386~$ ls -l /sys/block/nbd0/pid
ls: cannot access /sys/block/nbd0/pid: No such file or directory
--
Paul
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