binwalk boot0.img

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             Flattened device tree, size: 15713958 bytes, version: 17
220           0xDC            LZ4 compressed data
94008         0x16F38         SHA256 hash constants, little endian
6051398       0x5C5646        SHA256 hash constants, little endian
6051684       0x5C5764        AES Inverse S-Box
6371072       0x613700        Certificate in DER format (x509 v3), header length: 4, sequence length: 676
6558378       0x6412AA        Certificate in DER format (x509 v3), header length: 4, sequence length: 16
7005907       0x6AE6D3        xz compressed data
8298440       0x7E9FC8        Flattened device tree, size: 89400 bytes, version: 17
8388044       0x7FFDCC        gzip compressed data, maximum compression, from Unix, last modified: 2020-12-03 06:14:33
根据上面的起始点信息，推测出各个镜像位置，然后用dd从指定位置开始提取
huawei@foropenwrt:~$ dd if=boot0.img of=ramdisk.gz bs=1 skip=8388044

12583476+0 records in
12583476+0 records out
12583476 bytes (13 MB, 12 MiB) copied, 74.0925 s, 170 kB/s
huawei@foropenwrt:~$
huawei@foropenwrt:~$ gunzip ramdisk.gz