I have been trying all week to mount USB drive on MR2040 running custom OpenWrt image.
It seems that the CRC32 module is not getting loaded, and I cannot mount the drive to move my rootfs.

TP-Link MR2040 on image built from 15.05.1-ar71xx-generic.Linux-x86_64, having all ext4 and USB packages included.

fdisk on linux:
root@kali:~# fdisk -l /dev/sdb
Disk /dev/sdb: 14.9 GiB, 16018046976 bytes, 31285248 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xca51a7ae

Device     Boot   Start      End  Sectors  Size Id Type
/dev/sdb1          2048  4196351  4194304    2G 82 Linux swap / Solaris
/dev/sdb2       4196352 31285247 27088896 12.9G 83 Linux

dmesg says:
[  249.350000] usb 1-1: new high-speed USB device number 2 using ehci-platform
[  249.940000] usb-storage 1-1:1.0: USB Mass Storage device detected
[  249.960000] scsi host0: usb-storage 1-1:1.0
[  251.170000] scsi 0:0:0:0: Direct-Access     Lexar    USB Flash Drive  8.07 PQ                    : 0 ANSI: 4
[  251.180000] sd 0:0:0:0: [sda] 31285248 512-byte logical blocks: (16.0 GB/14.9                     GiB)
[  251.190000] sd 0:0:0:0: [sda] Write Protect is off
[  251.190000] sd 0:0:0:0: [sda] Mode Sense: 23 00 00 00
[  251.200000] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doe                    sn't support DPO or FUA
[  251.640000]  sda: sda1 sda2
[  251.650000] sd 0:0:0:0: [sda] Attached SCSI removable disk

On mounting /dev/sda2 [mount /dev/sda2 /mnt/lexar:
mount: mounting /dev/sda2 on /mnt/lexar failed: No such file or directory

dmesg says:
[  760.480000]  sda: sda1 sda2
[  760.490000] sd 1:0:0:0: [sda] Attached SCSI removable disk
[  805.060000] EXT4-fs (sda2): Cannot load crc32c driver.

The crc16 module is already loaded, as are the USB dependencies.

Anyone any clue why is this error coming up??

Cheers & Happy 2017!!!

download kmod-lib-crc32c and kmod-crypto-crc32c

(Last edited by jaohozbn on 1 Jan 2017, 17:38)

The problem is with the machine you used to format the pendrive, try to use an older kernel pc, such as Debian 7/8 or Ubutu 14.04. For me it worked because I was formatting in deepin 15.3 with kernel 4.4.

Thank you jaohozbn!

Hi,
Modules downloaded, .ko extracted and placed in /lib/modules/*/, dependencies added to /etc/modules-boot.d/, fstab edited, pivot-overlay created in /mnt.
Still having error automounting sda2: Cannot load crc32c driver.  Whereas sda3 got automounted OK as /home.

Please help
My USB drive sits in Huawei 3G modem's microSD slot.

(Last edited by giko on 28 Apr 2017, 10:17)

Any reason to do all that work instead of just installing the packages?

I have a 4meg (low memory) router with only one usb port in it.

dmesg
[    7.240000] scsi 0:0:0:0: Direct-Access     HUAWEI   TF CARD Storage       PQ: 0 ANSI: 2
[    7.250000] random: procd urandom read with 11 bits of entropy available
[    7.260000] sd 0:0:0:0: [sda] 3948544 512-byte logical blocks: (2.02 GB/1.88 GiB)
[    7.290000] sd 0:0:0:0: [sda] Write Protect is off
[    7.290000] sd 0:0:0:0: [sda] Mode Sense: 0f 0e 00 00
[    7.290000] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[    7.330000]  sda: sda1 sda2 sda3
[    7.340000] sd 0:0:0:0: [sda] Attached SCSI removable disk

[   11.090000] mount_root: loading kmods from internal overlay
[   11.560000] jffs2: notice: (294) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[   11.580000] block: attempting to load /tmp/jffs_cfg/upper/etc/config/fstab
[   11.600000] EXT4-fs (sda2): Cannot load crc32c driver.
[   11.610000] block: extroot: mounting /dev/sda2 (ext4) on /tmp/extroot/overlay failed: -1 (Unknown error -1)
[   11.650000] jffs2: notice: (291) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[   11.670000] mount_root: loading kmods from internal overlay
[   11.950000] block: attempting to load /tmp/jffs_cfg/upper/etc/config/fstab
[   11.980000] EXT4-fs (sda2): Cannot load crc32c driver.
[   11.980000] block: extroot: mounting /dev/sda2 (ext4) on /tmp/extroot/overlay failed: -1 (Unknown error -1)
[   12.000000] mount_root: switching to jffs2 overlay

[   12.090000] procd: - early -
[   12.090000] procd: - watchdog -

[   13.040000] procd: - ubus -
[   13.730000] Adding 72256k swap on /dev/sda1.  Priority:-1 extents:1 across:72256k
[   14.030000] EXT4-fs (sda3): Cannot load crc32c driver.
[   14.070000] procd: - init -

this file has been obseleted. please call "/sbin/block mount" directly
[   26.460000] random: nonblocking pool is initialized
block: /dev/mtdblock5 is already mounted
[   26.540000] EXT4-fs (sda3): mounted filesystem with ordered data mode. Opts: data=ordered,errors=remount-ro
- init complete -

(Last edited by giko on 29 Apr 2017, 02:13)

SOLVED!
Downloading is not enough. You need to create /etc/modules.d/04-crypto-crc32c   with contents as follows:

crc32c_generic

and have  /etc/modules-boot.d/04-crypto-crc32c symlinked  to it.

(Last edited by giko on 25 May 2017, 07:42)