Hi,

I have been trying to download ChIP-seq data using SRA-toolkit. 

    prefetch -v SRR4032857

I get an error

>   Maximum file size download limit is 20,971,520KB
> 
> 2017-01-03T09:32:45 prefetch.2.3.5 err: error unexpected while
> resolving tree within virtual file system module - failed to resolve
> accession 'SRR925811' - Obsolete software. See
> https://github.com/ncbi/sra-tools/wiki ( 406 )
> 
> Redirected!!!
> 
> 2017-01-03T09:32:46 prefetch.2.3.5 err: name incorrect while
> evaluating path within network system module - Scheme is 'https'
> 2017-01-03T09:32:46 prefetch.2.3.5 err: path not found while resolving
> tree within virtual file system module - 'SRR925811' cannot be found.

I checked my hard disk space and also changed the default download folder from ./vdb-config -i. I downloaded the SRA-toolkit version 2.8.1.

What could be the issue and how can i resolve it?
As per the link in the error message, SRA has moved from HTTP to HTTPS, rendering all previous versions of the SRA toolkit obsolete.  You say you downloaded 2.8.1, but you still appear to be running 2.3.5, so I'd check what version is in your `$PATH` and where you installed the latest version.