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unsquashfs filesystem.squashfs
cd squashfs-root/

mount --bind /dev dev/
cd squashfs-root/
mount --bind /dev dev/
mount --bind /dev/pts/ dev/pts/
mount --bind /run run/
mount -t proc proc proc/
mount -t sysfs sysfs sys/
chroot .

===== 操作-----
apt-get install dde
exit

umount proc/
umount sys/
umount run/
umount dev/pts/
umount dev/
mksquashfs squashfs-root/ filesystem.squashfs