# external usb drive disappears



## ProServ (May 23, 2021)

Hi,
Crazy issue, but I've resolved it.


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## mer (May 23, 2021)

Sometime USB hubs can power down ports, I ran into that a while ago on Linux systems.  Maybe something configured with "power management" is powering down the port because there is no activity to the external drive.
maybe "sysctl -a | grep usb | grep power" can give a hint or two.


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## ProServ (May 23, 2021)

Hi, thanks for responding. It was actually somewhat embarrising because it turned out to be an extremely loose connection from the power supply. Had to change AC source and then it was fine.


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## judd (May 23, 2021)

mer said:


> Sometime USB hubs can power down ports, I ran into that a while ago on Linux systems.  Maybe something configured with "power management" is powering down the port because there is no activity to the external drive.
> maybe "sysctl -a | grep usb | grep power" can give a hint or two.



Hello!
mer just out of curiosity, what do these values mean that the console throws with your commands ?

`% sysctl -a | grep usb | grep power
hw.usb.disable_port_power: 0
hw.usb.power_timeout: 30
hw.usb.timings.extra_power_up_time: 20
hw.usb.timings.port_powerup_delay: 300`

Thank you.


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## mer (May 23, 2021)

ProServ  nice that it was that simple.  "note to self, always check physical connections, including power first"
judd  I'm not 100% sure so taking a guess (grep source tree would probably help):
disable_port_power, probably a boolean, could mean "don't allow a usb port to provide power" or "don't power off ports"
power_timeout, maybe "wait this long after powering up something to go check it.  If it's not ready in this time, error"
The other two are probably similar to the power_timeout, but modify behavior  on an error.


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## judd (May 23, 2021)

mer said:


> ProServ  nice that it was that simple.  "note to self, always check physical connections, including power first"
> judd  I'm not 100% sure so taking a guess (grep source tree would probably help):
> disable_port_power, probably a boolean, could mean "don't allow a usb port to provide power" or "don't power off ports"
> power_timeout, maybe "wait this long after powering up something to go check it.  If it's not ready in this time, error"
> The other two are probably similar to the power_timeout, but modify behavior  on an error.


I understand and with your explanation, it helps me to understand something.
Thank you again !


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