I was downloading a big file with wget, but the speed was very slow. How can I continue downloading this file with axel or aria2?
Sorry, axel uses its own algorithm to split chunks and download them in parallel to one destination file. If you try with axel, it will overwrite the incomplete file and start from the beginning.
There isn't really a way to do this unless you manually (hex-editor, etc.) re-sort the incomplete file into the internal format used by Axel.
The same applies to aria2; it will also refuse to continue downloading an incomplete file not started with it. In that case, you would have to modify the filename.aria2 metadata somehow to trick aria2c into resuming the file...
