I was looking at the udev information but couldn't find out anywhere. What does DEVLINKS signify also what are these values dev/disk/by-id/mmc-008G30_0xf281d20d & /dev/disk/by-path/platform-3400000.sdhci ?
DEVLINKS are unique names for a given device. In this case this is a a mass storage device, mmcblk0. The 2 DEVLINKS that this command is returning can be used when you want to address this storage device to query against it or reconfigure it.
You'll typically see devices go by multiple names, in this case the SD card is identifying itself as (by-id) mmc-008G30_0xf281d20d. The by-path typically shows where the device maps into your system's busses (think USB, PCI, etc).
Is there any significance in the names?
I believe the names are driven from the system's motherboard chipset + the devices themselves.
For example on my system, my
/dev/sda device =
/dev/disk/by-path/pci-0000:00:01.1-ata-1.0, the numbers are the "coordinates" of where this device resides in the PCI bus (pci-0000:00:01.1) and the
ata-1.0 corresponds with the Linux "drivers" that are being used to manage the device.
Here's another one that's for the
/dev/ttyUSB0 device - /
dev/serial/by-path/pci-0000:00:1d.1-usb-0:2:1.0-port0. This one shows the PCI bus but its the USB driver which is the "driver" for this device.