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I have a file.img file which was obtained by running dd if=/dev/sda of=file.img. This was done on a device with two partitions, /dev/sda1 and /dev/sda2. In order to flash a new device with the same image, I'm booting an Alpine Linux using network boot, copy the file.img from the network and run the dd if=file.img of=/dev/sda. This is competed successfully and if I reboot, the device boots up properly.

The issue is that I want to add some files to the new device. Naturally, I thought I'll just mount the /dev/sda2 (that's the device I want to add stuff to) and add stuff there. Well, not that simple: /dev/sda2 is missing - sometimes. After the dd command runs, sometimes - without a pattern observed - the partitions are missing. Checking the disk using fdisk -l /dev/sda shows both partitions there.

Running partprobe /dev/sda; dmesg always shows (dmesg command outputs this) sda: sda1 sda2 so the partitions are there and they're being recognized. Still, they don't appear under /dev/.

The funny part is that running partprobe /dev/sda sometimes fixes the issue, other times it doesn't.

With all this madness, rebooting the device will ALWAYS boot correctly.

If anyone has any idea what I could try, I'd greatly appreciate the ideas.

Thank you.

P.S.: I also tried to run partx -uv /dev/sda. That tells me:

partition: none  disk: /dev/sda, lower: 0, upper: 0
/dev/sda: partition table type 'dos' detected
/dev/sda: partition #1 added
/dev/sda: partition #2 added

But the partitions still can't be found under /dev/sdaX

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  • What's the output of mount | grep devtmpfs? Commented Apr 5, 2024 at 12:45
  • Output of mount | grep devtmpfs: devtmpfs on /dev type devtmpfs (rw,nosuid,noexec,relatime,size=10240k,nr_inodes=498259,mode=755,inode64) Commented Apr 5, 2024 at 12:50
  • You're dealing with something funny/unsual. Could be your kernel. Commented Apr 5, 2024 at 12:54
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    As an aside, your use of dd is terribly inefficient. You will get much better throughout with a simple cat file.img >/dev/sda Commented Apr 5, 2024 at 13:50
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    @ChrisDavies I'm actually using pv with dd. To be honest, I didn't know cat is faster but I'll give it a go @ArtemS.Tashkinov well, that's what I'm saying, I don't configure anything in the kernel. I just boot alpine with whatever kernel settings it comes, dd and then try to mount the drive. Anyways, I found that I can actually create the missing devices using mknod: mknod -m 660 /dev/sda2 b 8 2 so the problem can be considered "fixed". Commented Apr 5, 2024 at 15:59

1 Answer 1

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For anyone looking for a solution to this, you can either:

  1. Create your device entry under /dev. An example for adding the /dev/sda2 follows:

mknod -m 660 /dev/sda2 b 8 2

  1. Try to run

mdev -s

The 2nd command made my life easier and, so far it works without any issues. Mdev's man page:

Usage:
    mdev [-vS] 

        -v        Verbose
        -S        Log to syslog too
        -s        Scan /sys and populate /dev
        -d        Daemon, listen on netlink
        -f        Run in foreground
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