I've tried to install version 1.1.9 didn't work,
system/logs/error.txt  showed error:

Error: Unable to access or write to cache directory /var/www/username/data/www/sitename.com/store/system/cache/

Folder "cache" was 777 with right group and user-owner, accessible for writing for all users - 100%.

Tried many times with different folder permissions, didn't work.

Then I realized that I have a new php version, (had already this issue on my server before, Dmitriy fixed it)
and I changed in core/lib/cache.php

$cache_files = glob( DIR_CACHE. '*/*', GLOB_NOSORT);
if(!is_array($cache_files)

to

$cache_files = glob( DIR_CACHE. '*/*', GLOB_NOSORT);
if(!is_array($cache_files) || !is_writeable(DIR_CACHE))

And then installation completed successfully!

Imported all data from old sql, transferred pictures folders and storefront.
And now my old site is up again!

Had problem with additional languages, but also fixed them..

Thx webdevmerc for advises.
Thx abolabo for fixing "cache" problem

I haven't tried it myself, but assuming you have access to PhpMyadmin, a way I would do this is install the new Abantecart version with sample data...export the data...Look at how the columns are setup.

Afterwards, get my old data from the old system, convert all the table data to what the new system wants, re-import.

This doesn't really install anything from the old set and is time consuming, but it's what I'd do since importing and having constant errors is a worst situation IMO than taking the painstaking time to clean up the old data.

Another method of course is to install your previous version of Abantecart.  Import all the data in that version, then slowly upgrade every version that was missed to the latest spec.  This might be easier and probably worth a look as well since as your system isn't live, if it doesn't work, it may save you a lot of time depending on how much conversion you'd have to do with the 1st method above.

Thank you, I like the second method you mention.
I would try it. I have PhpMyadmin, so I'll import all data with the right prefix from old database.

Where to find which version I had before?

 made them 777 www-data or root for user and group.
Nothing helps..

folder "cache" and "system" 777 www-data, as I already tried before, doesn't help.

Nothing stops PHP to create folder "settings" and three files inside.

Nothing changed...

Still can not enable cache option... in settings
no error shows, as usual: looks like saved successfully, but after page refresh shows not saved again.

what change is that no "index.html" file anymore (as I deleted everything in cache as you asked), folder "settings" was recreated with three files inside.

When clearing configuration cache shows as usual:


Message status:
    critical

Date:
    10/07/2015 01:31:07 PM

Number of repetitions:
    2

Error: Unable to access or write to cache directory /var/www/username/data/www/sitename.com/system/cache/ Cache feature was disabled. Check permissions on directory and enable setting back.

May be I cant explain perfectly, not sure why you can't get what I mean.

I already wrote this folders are 777 and all subfolders.
folder cache/settings/ has files inside and they are update automatically everyday.

"Error: Unable to access or write to cache directory /var/www/username/data/www/sitename.com/system/cache/ Cache feature was disabled. Check permissions on directory and enable setting back."
which shows when I clean cache for "Configuration"  - System and store configurations

Set 0777 for system/cache/ directory and subdirectories

The QUESTION IS THE SAME:

Does anyone knows, why just [cache enabled] "ON" doesn't want to be saved? For all other settings, changes are saving correctly...

folders are 777 and subfolders too.

So, no help at all?
no one knows, why just cache enabled "ON" doesn't want to be saved? For all other settings, changes are saving correctly...

eCommerce Core, thank you, but what you write is obvious, It's first thing I've done 4 days ago, and this was checked hundreds times already by me, I need real solution. I've read the installation instruction by myself.

After that set below directories and all files/dirs under to read/write/execute (777)

system/cache
system/logs
system/cache
image
image/thumbnails
download
extensions (only if you plane to install extensions)
resources
admin/system/backup

1. why would you write:
image
image/thumbnails

"all files/dirs under to read/write/execute"
if all files/dirs under "image" would be 777, means image/thumbnails already 777...

2. Following installation guide, it should be just directories 777,
then why /image/thumbnails/index.html all the sudden required to be 777?
this file there just to hide the directory from a user access.

Found out, which cache return error when I try to clean it.
 Error return just by one of them:

Configuration    System and store configurations

Error: Unable to access or write to cache directory /var/www/username/data/www/sitename.com/system/cache/ Cache feature was disabled. Check permissions on directory and enable setting back.

I've set chmod 777 for files
    
/system/cache/index.html
/system/logs/index.html

But it didn't help...

What does it mean? "enable setting back" How, I can do it.
The error shows, when I clean all cash data, folders and sub-folders are 777..