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I have a bootable USB Linux. Occasionally, someone will disconnect the USB power and bash would complain any command was not found. Even if I reconnect the drive, dmesg said the drive has been detected, all the commands were still unusable. Any way to remount the root partition without reboot?

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You could try the remount option: mount -o remount, which is also used to e.g. make a read-write filesystem read-only (remount it read-only). This should force mount to renew the connection. For details, just take a look at man mount.

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Thanks for the answer, but I'm not sure if mount command is available after this catastrophic event happen. I'll try it out next time when this happens. – Patrick Jul 4 '12 at 16:52
Indeed, this does not work for me when the pen drive is pulled out and plugged back in. I get a bunch of "command not found" error messages when I try to sudo mount -o remount / – Joey Adams Feb 13 '13 at 6:56
@JoeyAdams behaviours differs with e.g. different file systems and other conditions. I remember e.g. broken Samba shares where a hard case, as sometimes the system won't let go of the "old mounts" (the broken ones), and thus you could not renew them. I have no "100% sure" solution, sorry -- which is why I wrote "You could try". Sometimes it does work, other times it does not... – Izzy Feb 13 '13 at 7:49

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