LZMA is one of the best compression algorithms and Squashfs is one of the best compressed filesystems available nowadays. This project combined both to make something even better. 

LZMA can compress much better then gzip, which was the only option in squashfs for years. Compressing to LZMA format is very slow, but this is not a problem as the squashfs filesystem needs to be compressed only once. Then it's only read million times; so what we care about is the speed of decompression. LZMA decompression is slower than gzip, but it's even very fast, about 10-20 MB/s on a 2GHz CPU. 

解压后直接make，但是安装的时候碰到一个问题

/usr/bin/ld: mksquashfs.o: undefined reference to symbol 'log10@@GLIBC_2.0'
/usr/bin/ld: note: 'log10@@GLIBC_2.0' is defined in DSO /lib/libm.so.6 so try andding it to the linker command line
/lib/libm.so.6: could not read symbols: Invalid operation

这是由于编译的时候没有链接math库。

追踪溯源，找到了“squashfs3.2-r2/squashfs-tools”目录下Makefile文件，在

mksquashfs: LDLIBS += -lpthread -lunlzma_r -llzma_r -lstdc++

后面加上 -lm

然后编译，就通过了