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When increasing the size of a virtual disk, I need the (guest) Linux to recognize the change before I can grow partitions/volumes in the guest system. A reboot does this, but is it possible to have the system re-detect disk sizes without a reboot (to avoid unnecessary downtime)?
For SCSI disks (/dev/sdX) this can be accomplished by rescanning the bus:
echo 1 > /sys/class/block/sdX/device/rescan
Replace sdX with the name of your actual disk.