Property:linux.bin

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BoxMatrix >> Configuration >> linux.bin

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Binary-File

Binary:	linux.bin   -   type Blob	Wiki	Freetz	IPPF	whmf	AVM	Web
Location:	Configuration >> Binary-Files   -   Origin: AVM
Path:	Release: /etc/fw Lab+Rel: /etc/fw
Properties:	Size: 3.5M   -   Firmware: 7.30
Function:	Kernel + filesystem of the RTL86 modem linux.

Goto:   Dependencies   -   Model-Matrix   -   SMW-Browser

Details

This file moved to vm.img in fw 7.31. The facts below are still valid.

linux.bin is the 800 kB squashfs and 2.7 MB kernel of the 7520v2 secondary Linux running on the RTL86 modem chipset.

It has an unusual structure, a 64 bytes header followed by the squashfs followed by the kernel.
It is booted by the 31 kB bootloader boot.bin.

me@home:~$ hd -n 128 linux.bin

00000000  a0 00 00 03 80 00 00 00  00 37 e6 e1 80 00 00 00  |.........7......| <- 64 bytes header
00000010  c5 73 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |.s..............|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 b4 10 00 00  |................|

00000040  68 73 71 73 8a 01 00 00  32 0b 3b 62 00 00 02 00  |hsqs....2.;b....| <- squashfs start
00000050  0f 00 00 00 04 00 11 00  e0 02 02 00 04 00 00 00  |................|
00000060  d3 09 56 04 00 00 00 00  88 38 0c 00 00 00 00 00  |..V......8......|
00000070  80 38 0c 00 00 00 00 00  ff ff ff ff ff ff ff ff  |.8..............|

The kernel is LZMA compressed, and huge. 2.7 MB compressed and 6.9 MB extracted:

me@home:~$ binwalk linux.bin

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
64            0x40            Squashfs filesystem, little endian, version 4.0, compression:xz, 
         size: 800904 bytes, 394 inodes, blocksize: 131072 bytes, created: 2022-03-23 11:57:38
802880        0xC4040         LZMA compressed data, properties: 0x5D, dictionary size: 8388608 
         bytes, uncompressed size: 7195520 bytes

It's easy to strip off the 64-bytes header.

me@home:~$ dd if=linux.bin of=squashfs.bin bs=64 skip=1

57243+1 records in
57243+1 records out
3663585 bytes (3.7 MB) copied, 0.147585 s, 24.8 MB/s

Let's analyze it:

me@home:~$ unsquashfs -s squashfs.bin

Found a valid SQUASHFS 4:0 superblock on squashfs.bin.
Creation or last append time Wed Mar 23 12:57:38 2022
Filesystem size 782.13 Kbytes (0.76 Mbytes)
Compression xz
Block size 131072
Filesystem is exportable via NFS
Inodes are compressed
Data is compressed
Fragments are compressed
Always-use-fragments option is specified
Xattrs are not stored
Duplicates are removed
Number of fragments 15
Number of inodes 394
Number of ids 2

Let's split and unpack the kernel:

me@home:~$ dd if=linux.bin of=kernel.bin bs=1 skip=802880

2860769+0 records in
2860769+0 records out
2860769 bytes (2,9 MB, 2,7 MiB) copied, 4,7228 s, 606 kB/s

me@home:~$ cat kernel.bin | unlzma > kernel2.bin

Now let's see the kernel version:

me@home:~$ strings kernel2.bin | grep 'Linux '

Linux version 3.18.20 (mwaeltermann@a1d31305b02b) (gcc version 4.8.5 20150209 (prerelease) (Realtek MSDK-4.8.5p1 Build 2220) ) #13 SMP Wed Mar 23 11:57:42 UTC 2022 [SDK 2.4.1-p13]
No working init found.  Try passing init= option to kernel. See Linux Documentation/init.txt for guidance.  

Model-Matrix

Daily updated index of the presence, path and size of this binary for each model. Last update: 2024-04-19 05:14 GMT.
Showing all models using this binary. Click any column header (click-wait-click) to sort the list by the respective data.
The (main/scrpn/boot/arm/prx/atom) label in the Model column shows which CPU is meant for models with multiple Linux instances.
Note that this list is merged from Firmware-Probes of all known AVM firmware for a model, including Recovery.exe and Labor-Files.

Model	Firmw	Path	Size
FRITZ!Box 7520 v2 (arm)	7.30	/etc/fw	3.5M
1 model uses this binary

SMW-Browser

Property:linux.bin

Information is currently being retrieved from the backend.