Mount USB hard drive on boot

Nerves Forum Nerves Questions / Help
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1

I’m trying to mount a USB hard drive on my nerves device at boot, I am using a custom system, so I have some flexibility.

But I’ve tried adding a -m directive to my erlinit.config as well as just mounting it in my application and it isn’t working.

If I am mounting to /root/uns/ does the filesystem on the USB drive have to match the file system on the card?

I added the ExFat and ExFat utilities to my system, and I tried using exfat as a disk format, and others. What disk format should I be using?

Any other ideas are welcome. My goal is to get postgres and influx installed and saving their data to the USB drive as well as a Phoenix app that can store uploads there.

Thanks in advance!

2

The device is found at startup:
00:00:10.079 [info] usb 2-1: new SuperSpeed Gen 1 USB device number 2 using xhci_hcd
00:00:10.079 [info] usb 2-1: New USB device found, idVendor=0bc2, idProduct=ab30, bcdDevice= 1.08
00:00:10.079 [info] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
00:00:10.079 [info] usb 2-1: Product: BUP RD
00:00:10.079 [info] usb 2-1: Manufacturer: Seagate
00:00:10.081 [info] usb 2-1: SerialNumber: NA9F8S18

I’m trying to mount it as /dev/sda1 . Trying /dev/sdb1 (since the usb designation is 2-1) doesn’t yield anything.

3

-m /dev/sda1:/root/unsilo:exfat:defaults

in the erlinit.config seems to have no effect.

As part of my application startup I have gotten to the point where:
System.cmd(“mount”, ["/dev/sda1", “/root/unsilo/”])

will get me

14:44:42.088 [info] trying to mount device
14:44:42.144 [info] F2FS-fs (sda1): Magic Mismatch, valid(0xf2f52010) - read(0x0)
14:44:42.144 [error] F2FS-fs (sda1): Can’t find valid F2FS filesystem in 1th superblock
14:44:42.166 [info] F2FS-fs (sda1): Magic Mismatch, valid(0xf2f52010) - read(0x0)
14:44:42.167 [error] F2FS-fs (sda1): Can’t find valid F2FS filesystem in 2th superblock
14:44:42.167 [info] F2FS-fs (sda1): Magic Mismatch, valid(0xf2f52010) - read(0x0)
14:44:42.174 [error] F2FS-fs (sda1): Can’t find valid F2FS filesystem in 1th superblock
14:44:42.181 [info] F2FS-fs (sda1): Magic Mismatch, valid(0xf2f52010) - read(0x0)
14:44:42.189 [error] F2FS-fs (sda1): Can’t find valid F2FS filesystem in 2th superblock

Does it need to be f2fs ? Thats seems like it’s for flash devices. Is it OK to format a USB HD like that? I would prefer expat so I can mount it on a mac if needed.

4

It doesn’t need to be F2FS. When you don’t specify a filesystem format, mount tries the filesystems that are available and F2FS is particularly verbose.

Try passing the filesystem type that you want to mount by using -t option.

You can get the list of available filesystem drivers by reading /proc/filesystems. If you don’t see the one that you want, you’ll need to update the Linux kernel configuration to included it. I’m pretty sure that vfat is what you want and that should already be enabled.

Also, as you noticed erlinit runs way too early in the boot process and Linux hasn’t enumerated the USB drive yet. Mounting filesystems in erlinit is really only intended for pseudo filesystems (like those under /sys) and things needed before any Elixir code is run (like the application partition so that the the command line history file can be initialized or read).

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5

I updated the linux kernel to include ext4 file system, however I still cannot mount an external hard drive.

iex(48)> cmd("mount /dev/sda1 /data/media")

16:52:20.775 [info] F2FS-fs (sda1): Magic Mismatch, valid(0xf2f52010) - read(0x0)

16:52:20.775 [error] F2FS-fs (sda1): Can't find valid F2FS filesystem in 1th superblock

iex(50)> cmd("mount -t ext4 /dev/sda1 /data/media")
mount: mounting /dev/sda1 on /data/media failed: Invalid argument
255

Any idea why this error ?

6

Could you double check that ext4 is available by running cat "/proc/filesystems"?

I’m wondering if the kernel option to enable EXT4 didn’t take effect. Like maybe the kernel wasn’t rebuilt after the config changed.

7

I looked at that before and ext4 is available

iex(test@nerves-a391)1> cmd("cat /proc/filesystems")

nodev   sysfs
nodev   tmpfs
nodev   bdev
nodev   proc
nodev   cgroup
nodev   cgroup2
nodev   cpuset
nodev   devtmpfs
nodev   configfs
nodev   sockfs
nodev   pipefs
nodev   ramfs
nodev   devpts
        ext3
        ext2
        ext4
        squashfs
        vfat
        f2fs
nodev   mqueue
nodev   pstore
0
8

Finally, I was able to mount the hard drive. There’s an issue related to version or architecture differences between x86_64 and arm64. I cross-compiled the e2fsprogs, copied the mkfs.ext4 to the nerves image, formatted the hard drive and I was about to mount it without any issue.

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