I am trying to get access to the BusyBox Shell and if possible to get a firmware dump.

The "U-Boot" has limited possibilities but what is good is "sf - SPI flash sub-system".

Can anyone help me get access to the shell? Or a dump of the whole firmware without SOIC8 clip.

I use a UART interface on the hardware:

Starting kernel ...

Linux version (root@grant-virtual-machine) (gcc version 4.4.6 (Realtek RSDK-1.5.6p2) ) #141 Mon Jun 17 11:13:56 CST 2019 [luna SDK 1.0.51]
CPU revision is: 0000dc02
Determined physical RAM map:
 memory: 02eff000 @ 00000000 (usable)
 memory: 00eff000 @ 03000000 (usable)
II: Kernel command line modified: mtdparts=rtk_spi_nor_mtd ->   mtdparts=physmap-flash
Zone PFN ranges:
  Normal   0x00000000 -> 0x00003eff
Movable zone start PFN for each node
early_node_map[2] active PFN ranges
    0: 0x00000000 -> 0x00002eff
    0: 0x00003000 -> 0x00003eff
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 15744
Kernel command line: console=ttyS0,115200   mtdparts=physmap-flash:256K(boot),8K(env),8K(env2),1776K(config),4M(k0),10M(r0) root=31:5
root_dev_setup line 180 root: 31:5
icache: 64kB/32B, dcache: 32kB/32B, scache: 0kB/0B
PID hash table entries: 256 (order: 8, 1024 bytes)
console [ttyS0] enabled
U-Boot 2011.12.M (Sep 29 2017 - 16:08:09)

SPI-F: EF4018/MMIO16-1 1x16 MB (plr_flash_info @ 83c23714)
Loading 8192B env. variables from offset 0x40000
Loading 8192B env. variables from offset 0x42000
*** Warning - bad CRC, using default environment

Loaded 8192B env. variables from offset 0x40000
mtdparts0=mtdparts=rtk_spi_nor_mtd:256K(boot),8K(env),8K(env2),1776K(config),4M(k0),10M(r0) root=31:5
Warning: eth device name has a space!

Hit any key to stop autoboot:  0
## Booting kernel from Legacy Image at 94200000 ...
   Image Name:   Linux Kernel Image
   Created:      2019-06-17   3:16:33 UTC
   Image Type:   MIPS Linux Kernel Image (lzma compressed)
   Data Size:    2528816 Bytes = 2.4 MB
   Load Address: 80000000
   Entry Point:  80000000
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK
bootcmd=setenv bootargs ${bootargs_base} ${mtdparts0};bootm ${img0_kernel}
erase_cfgfs=sf erase ${fl_cfgfs} +${fl_cfgfs_sz}
erase_env=sf erase ${fl_env} +${fl_env_sz};sf erase ${fl_env2} +${fl_env_sz}
ethact=LUNA GMAC

fx1000_init=mw bb000084 00000048
mtdparts0=mtdparts=rtk_spi_nor_mtd:256K(boot),8K(env),8K(env2),1776K(config),4M(k0),10M(r0) root=31:5
sgmii_init=mw bb000084 00000044
upb=tftp 80000000 plr.img; crc32 ${fileaddr} ${filesize}; sf erase 0 +${fl_boot_sz}; sf write ${fileaddr} 0 ${filesize}
upk=tftp 80000000 uImage; crc32 ${fileaddr} ${filesize}; sf erase ${fl_kernel1} +${fl_kernel1_sz}; sf write ${fileaddr} ${fl_kernel1} ${filesize}
upr=tftp 80000000 rootfs; crc32 ${fileaddr} ${filesize}; sf erase ${fl_rootfs1} +${fl_rootfs1_sz}; sf write ${fileaddr} ${fl_rootfs1} ${filesize}
upv=tftp 80000000 vm.img;upvmimg ${fileaddr}
yu=loady 80000000; cp.b 80000000 81000000 ${filesize}; cmp.b 80000000 81000000 ${filesize}; sf erase 0 ${filesize}; sf write 80000000 0 ${filesize}
Environment size: 1442/8187 bytes`
#md 94200000
94200000: 27051956 2d28951a 5d070611 00269630    '..V-(..]....&.0
94200010: 80000000 80000000 2f808b2c 05050203    ......../..,....
94200020: 4c696e75 78204b65 726e656c 20496d61    Linux Kernel Ima
94200030: 67650000 00000000 00000000 00000000    ge..............
94200040: 5d000000 013c76b6 00000000 00000600    ]....<v.........
94200050: 0395c7e8 666e5ec6 cddf5cd3 7f860981    ....fn^...\.....
94200060: 66e4e47d 16454378 ba7286d7 10ac0e5f    f..}.ECx.r....._
94200070: f4548875 7fd45d23 8321e1d6 6fac3711    .T.u..]#.!..o.7.
94200080: a7076c68 3c27aa4a b8951c97 f585008d    ..lh<'.J........
94200090: ec4f63f7 f8f232aa 1ce8ee62 fc24a98f    .Oc...2....b.$..
942000a0: 333ae099 be5ca694 d30dce2b a68c092e    3:...\.....+....
942000b0: 12e311f5 86510704 357b1219 64c20547    .....Q..5{..d..G
942000c0: eaed521e e00f8734 f0708316 d5433715    ..R....4.p...C7.
942000d0: 285ceb11 2f3b455b 69650bef d9a0f557    (\../;E[ie.....W
942000e0: 1ae81e50 d473f125 bdfe34b3 e3cdab52    ...P.s.%..4....R
942000f0: 3db532b3 8ccfc480 559a1511 a90508ff    =.2.....U.......
?               - alias for 'help'
base            - print or set address offset
bdinfo          - print Board Info structure
boot            - boot default, i.e., run 'bootcmd'
bootd           - boot default, i.e., run 'bootcmd'
bootm           - boot application image from memory
bootp           - boot image via network using BOOTP/TFTP protocol
btg             - bus traffic generator sub-system
cmp             - memory compare
coninfo         - print console devices and information
cp              - memory copy
crc32           - checksum calculation
echo            - echo args to console
editenv         - edit environment variable
env             - environment handling commands
go              - start application at address 'addr'
help            - print command description/usage
iminfo          - print header information for application image
imxtract        - extract a part of a multi-image
itest           - return true/false on integer compare
loadb           - load binary file over serial line (kermit mode)
loads           - load S-Record file over serial line
loady           - load binary file over serial line (ymodem mode)
loop            - infinite loop on address range
md              - memory display
mdram_test      - mdram_test   - do DRAM test.
mm              - memory modify (auto-incrementing address)
mtest           - simple RAM read/write test
mw              - memory write (fill)
nm              - memory modify (constant address)
printenv        - print environment variables
reset           - Perform RESET of the CPU
reset_all       - Perform whole chip RESET of the CPU
reset_sw        - Perform software RESET
run             - run commands in an environment variable
saveenv         - save environment variables to persistent storage
setenv          - set environment variables
sf              - SPI flash sub-system
sleep           - delay execution for some time
source          - run script from memory
tftpboot        - boot image via network using TFTP protocol
upvmimg         - update kernel and rootfs by vmimg format on luna platform
version         - print monitor, compiler and linker version
  • Hi could you share Realtek RSDK-1.5.6p2 • luna SDK V1.9.0 SDK ? Commented Dec 31, 2020 at 10:07

1 Answer 1


adding single to bootargs should drop you into a root shell, e.g. try:

setenv bootargs ${bootargs_base} single ${mtdparts0}
bootm ${img0_kernel}

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.