arch -powered usb hd not detected

[akcom]

Hi all, I just set up my rpi and I hit a bump in the road. I'm running the most up to date arch linux. My rpi is connected to the psu and also a powered usb hub. I have an external HD connected to the USB hub. Unfortunately the device does not show up under /dev/. In fact, I have nothing named sd[a-z] under /dev/ at all. Any assistance would be much appreciated!

Not sure why this is helpful, but I've seen it asked for in other threads:

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[root@alarmpi /]# lsusb -v | grep -iP "Transfer Type.*(Interrupt|Isochronous)" | wc -l
6

And the following, in case it helps:

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[root@alarmpi /]# grep SCSI /var/log/messages.log | tail -n 5
Jan  1 01:00:07 alarmpi kernel: [    1.831965] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
Jan  1 01:00:07 alarmpi kernel: [    1.880565] Loading iSCSI transport class v2.0-870.
Jan  1 01:00:07 alarmpi kernel: [    1.613062] SCSI subsystem initialized
Jan  1 01:00:07 alarmpi kernel: [    1.832014] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
Jan  1 01:00:07 alarmpi kernel: [    1.913045] Loading iSCSI transport class v2.0-870.
[root@alarmpi /]# dmesg | tail -n 5
[ 1096.777641] 0 pages swap cached
[ 1096.777841] smsc95xx 1-1.1:1.0: eth0: kevent 2 may have been dropped
[ 1096.797288] smsc95xx 1-1.1:1.0: eth0: kevent 2 may have been dropped
[ 1124.100966] mmc0: missed completion of cmd 18 DMA (512/512 [1]/[1]) - ignoring it
[ 1124.101103] mmc0: DMA IRQ 6 ignored - results were reset
[root@alarmpi /]# dmesg | grep -E "sd[a-z]"
[    0.000000] Kernel command line: dma.dmachans=0x7f35 bcm2708_fb.fbwidth=1824 bcm2708_fb.fbheight=984 bcm2708.boardrev=0xe bcm2708.serial=0x2b76f2a8 smsc95xx.macaddr=B8:27:EB:76:F2:A8 sdhci-bcm2708.emmc_clock_freq=100000000 vc-cma-mem=0/0x11800000@0xd400000 mem=0xc400000@0x0 mem=0x11800000@0xd400000 vc_mem.mem_base=0x1ec00000 vc_mem.mem_size=0x20000000  smsc95xx.turbo_mode=N dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=noop rootwait
[    2.334467] sdhci: Secure Digital Host Controller Interface driver
[    2.334481] sdhci: Copyright(c) Pierre Ossman
[    2.334588] sdhci: Enable low-latency mode
[    2.376489] sdhci-pltfm: SDHCI platform and OF driver helper

[DBryant]

Are you sure the USB hub has enough umph to power the hard drive correctly? Or is it independently powered? Can you plug it into another system to verify that it is functional?

Without the drive in place, run just run lsusb, then plug it in and repeat. Counting the number of instances of a particular string match is not that helpful in this case.
Can you identify the device that has been added?

You might also run df, without and without the drive present. You should be able to identify a new mount point for the drive, you might well find a line with /mnt or /media that has appeared during the addition of the drive. The full line will also indicate the device that has been created, not necessarily sd[a-z].

Observing /var/log/messages while doing the above exercises may well be enlightening. Use

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tail -f /var/log/messages

the limit to the last 5 lines in not that helpful unless iit encapsulates all of the chatter.