I need the update manager to only download a single package at a time and not try to download multiple packages at once.

My slow internet cannot handle multiple connections; slows the download to a crawl and some packages will reset themselves halfway through when they time-out.

EDIT

When using apt-get update multiple repositories get checked:


When using apt-get upgrade multiple packages are downloaded:



Question: ERR_SSL_PROTOCOL_ERROR in chrome 39 and 40 but works in chrome 36.Help fix in chrome 39
Answer: Google announced that they would begin removing support for SHA-1 cryptographic hash algorithm beginning with Chrome 39. According to Google:


  HTTPS sites whose certificate chains use SHA-1 and are valid past 1 January 2017 will no longer appear to be fully trustworthy in Chrome’s user interface.


There are several sites which can provide detailed analysis of your SSL certificate chain, such as Qualys SSL Labs' SSL Test.

Google Chrome does have a highly risky command-line option --ignore-certificate-errors which might bypass certain certificate errors. Be aware that ignoring certificate errors puts all of your SSL traffic at risk of being eavesdropped on.

It's also possible that this is a new bug. Google switched from using OpenSSL library to it's own "BoringSSL" library in Chrome 38. To report a bug in Chrome visit chrome://help/ and click "Report an issue".