Why can't I see the eMMC device after boot?

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
1

My jeston nano just show the sd_card(64g).

(1) “dmesg | grep mccblk” shows:
[ 0.000000] Kernel command line: tegraid=21.1.2.0.0 ddr_die=4096M@2048M section=512M memtype=0 vpr_resize usb_port_owner_info=0 lane_owner_info=0 emc_max_dvfs=0 touch_id=0@63 video=tegrafb no_console_suspend=1 console=ttyS0,115200n8 debug_uartport=lsport,2 earlyprintk=uart8250-32bit,0x70006000 maxcpus=4 usbcore.old_scheme_first=1 lp0_vec=0x1000@0xff780000 core_edp_mv=1075 core_edp_ma=4000 tegra_fbmem=0x800000@0x92cb6000 is_hdmi_initialised=1 root=/dev/mmcblk0p1 rw rootwait console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 root=/dev/mmcblk0p1 rw rootwait console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 rootfstype=ext4 root=/dev/mmcblk0p1 rw rootwait
[ 3.964891] mmcblk0: mmc0:aaaa SC64G 59.5 GiB
[ 3.970681] mmcblk0: p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12
[ 4.539487] mmcblk mmc0:aaaa: Card claimed for testing.
[ 4.965586] EXT4-fs (mmcblk0p1): mounted filesystem with ordered data mode. Opts: (null)
[ 6.377312] EXT4-fs (mmcblk0p1): re-mounted. Opts: (null)

(2) lsblk shows:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop0 7:0 0 16M 1 loop
mtdblock0 31:0 0 4M 0 disk
mmcblk0 179:0 0 59.5G 0 disk
├─mmcblk0p1 179:1 0 59.5G 0 part /
├─mmcblk0p2 179:2 0 128K 0 part
├─mmcblk0p3 179:3 0 448K 0 part
├─mmcblk0p4 179:4 0 576K 0 part
├─mmcblk0p5 179:5 0 64K 0 part
├─mmcblk0p6 179:6 0 192K 0 part
├─mmcblk0p7 179:7 0 576K 0 part
├─mmcblk0p8 179:8 0 64K 0 part
├─mmcblk0p9 179:9 0 640K 0 part
├─mmcblk0p10 179:10 0 448K 0 part
├─mmcblk0p11 179:11 0 128K 0 part
└─mmcblk0p12 179:12 0 80K 0 part

(3) “fdisk -l” shows:
Disk /dev/ram0: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram1: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram2: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram3: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram4: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram5: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram6: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram7: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram8: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram9: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram10: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram11: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram12: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram13: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram14: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram15: 8 MiB, 8388608 bytes, 16384 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/loop0: 16 MiB, 16777216 bytes, 32768 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Disk /dev/mtdblock0: 4 MiB, 4194304 bytes, 8192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

GPT PMBR size mismatch (25165823 != 124735487) will be corrected by w(rite).
Disk /dev/mmcblk0: 59.5 GiB, 63864569856 bytes, 124735488 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: D048AD43-24FD-4DED-B06E-7BB8ED98158C

Device Start End Sectors Size Type
/dev/mmcblk0p1 24576 124735454 124710879 59.5G Linux filesystem
/dev/mmcblk0p2 2048 2303 256 128K Linux filesystem
/dev/mmcblk0p3 4096 4991 896 448K Linux filesystem
/dev/mmcblk0p4 6144 7295 1152 576K Linux filesystem
/dev/mmcblk0p5 8192 8319 128 64K Linux filesystem
/dev/mmcblk0p6 10240 10623 384 192K Linux filesystem
/dev/mmcblk0p7 12288 13439 1152 576K Linux filesystem
/dev/mmcblk0p8 14336 14463 128 64K Linux filesystem
/dev/mmcblk0p9 16384 17663 1280 640K Linux filesystem
/dev/mmcblk0p10 18432 19327 896 448K Linux filesystem
/dev/mmcblk0p11 20480 20735 256 128K Linux filesystem
/dev/mmcblk0p12 22528 22687 160 80K Linux filesystem

that says my jeston nano just read a mmcblk0 and it is 64g sd_card. How can I see the 16g internal eMMC? and what is the /dev/ram, total 128M?

2

The Nano development kit doesn’t have the eMMC; that’s the production module (which isn’t available in volume yet.)

3

Thanks.

4

But what is /dev/ram in " /dev/ram1: 8 MiB"?

5

Ram disks are a common way to add content prior to disk being available (or sometimes just for performance). As an example, sometimes an “initrd” is used…if you are not familiar with that, it is just a minimal and mini Linux kernel and support which allows loading modules. The initrd is unpacked into RAM as if it is a hard disk. The advantage is that you can then load modules which otherwise are not available on the disk, while being needed to access the disk…it solves a “chicken and the egg” dilemma when you need a module to understand something special like a RAID controller (or perhaps encrypted filesystem) in order to read the driver to the RAID controller. Much of the “/dev/ram” content is related to supporting boot or boot devices in a portable way (the main kernel no longer requires additions, and additions needed to boot can be made via extra modules).