When you open http://cdimage.ubuntu.com/ubuntu/daily-live/ then there are 4 folders with ISO images of Ubuntu.
Two folders are named current/ and pending/
and two folders named after today's and yesterday's dates.
What are the differences/significance/purpose of the contents of these 4 different folders ?
There aren't four different folders. There are two named by date, and current is the same as the older of these two, and pending is the same as the newer of these two.
This seems to be the result of applying some automated testing to the ISOs. From this blueprint:
During the quantal cycle there have been times where the daily ISO images had bug or problems on them, which hit many users and or automated jenkins testing. Ideally we want to prevent users from downloading borked images and hitting/reporting bugs over and over again. We should discuss and possibly implement something to help with this, e.g.:
- consider uploading images to a staging area, running jenkins test and if jenkin tests pass then publish the iso images
- or for example push jenkin test failure notes to the cdimage / iso-tracker (like the oversize warning)
- think about potentially yanking borked images from cdimage.u.c
- communicate "why there was no daily build yet?", e.g. by pushing "FTBFS" notification to iso-tracker & cdimage.u.c
- communicate respin process in a more automatic way, e.g. on the iso tracker / cdimage.u.c
Objective:
- Try to run some automated testing before the images are published
- Work with Unity testing team to make sure unity works (hook unity jenkins to be dowstream from the desktop-default jenkins test)
pending is this staging area, as can be seen from the notes further down the blueprint page.
As for why have a set of folders based on dates and another set with names, it's easier:
current which always point to the current release, current and pending are symbolic links to folders containing the actual ISOs.