Install issues - 2.3 on CentOS7 - file permissions

I'm attempting to install Omeka-2.3 on a CentOS7 server - I have full access to the server. I've been working w/ a nest of mod_rewrite issues - trying every fix on these forums :) - am now working on the assumption that the rewrite check is flawed and attempting to continue install by going directly to install/install.php only now I'm getting permission errors "File storage not set up properly. The following error occurred when attempting to set up storage for your Omeka site: Directory not writable: '/var/www/html/omeka-2.3/files/thumbnails' Please ensure that all storage directories exist and are writable by your web server."
I have made user "apache" (which is the web server user in CentOS) both owner and group and even made the directories and files to mode 777 on the /omeka-2.3/files directory (checked all the files and directories are owned by the server and have open permissions) but still I get this error.
Is there any other way to get information about what omeka is trying to do? It's not a server or php error so those logs are not helpful and php info even inside those omeka directories reports all normal. Oh also the DNS / IP is all good I checked that too.

follow up - here is the .htaccess file - the document root is /var/www/html and I have omeka in a sub-directory called omeks-2.3 - this .htaccess is in that directory.

# Omeka .htaccess: Apache configuration file
# This file is required for Omeka to function correctly.

# --------------- #
# Error Reporting #
# --------------- #

# Uncomment the SetEnv line below to turn on detailed on-screen error
# reporting.
#
# Note: This should only be enabled for development or debugging. Keep this
# line commented for production sites.
#
SetEnv APPLICATION_ENV development

# ------------- #
# Rewrite Rules #
# ------------- #

RewriteEngine on

# If you know mod_rewrite is enabled, but you are still getting mod_rewrite
# errors, uncomment the line below and replace "/" with your base directory.
#

# the url for the site is http://hostname.edu/omeka-2.3
RewriteBase /omeka-2.3/

# Allow direct access to files (except PHP files)
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule !\.(php[0-9]?|phtml|phps)$ - [C]
RewriteRule .* - [L]

RewriteRule ^install/.*$ install/install.php [L]
RewriteRule ^admin/.*$ admin/index.php [L]
RewriteRule .* index.php

# -------------- #
# Access Control #
# -------------- #

# Block access to all .ini files.
<FilesMatch "\.ini$">
<IfModule mod_authz_core.c>
Require all denied
</IfModule>
<IfModule !mod_authz_core.c>
Order Allow,Deny
Deny from all
</IfModule>
</FilesMatch>

# --------#
# Caching #
# --------#

# Uncomment the lines below in order to enable caching of some files
# (after a finished site has gone live)
#
# <IfModule mod_expires.c>
# <FilesMatch "\.(js|ico|gif|jpg|png|css)$">
# ExpiresActive on
# ExpiresDefault "access plus 10 day"
# </FilesMatch>
# </IfModule>

# ------------ #
# PHP Settings #
# ------------ #

<IfModule mod_php5.c>
php_flag register_globals off
php_flag magic_quotes_gpc off
</IfModule>

one more update in case it's helpful here is the httpd.conf file...

#
# This is the main Apache HTTP server configuration file. It contains the
# configuration directives that give the server its instructions.
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
#
# [...boilerplate omitted for omeka forum pasting]
#
ServerRoot "/etc/httpd"

#
# Listen: Allows you to bind Apache to specific IP addresses and/or
# ports, instead of the default. See also the <VirtualHost>
# directive.
#
# Change this to Listen on specific IP addresses as shown below to
# prevent Apache from glomming onto all bound IP addresses.
#
#Listen 12.34.56.78:80
Listen 80

#
# Dynamic Shared Object (DSO) Support
#
# To be able to use the functionality of a module which was built as a DSO you
# have to place corresponding `LoadModule' lines at this location so the
# directives contained in it are actually available _before_ they are used.
# Statically compiled modules (those listed by `httpd -l') do not need
# to be loaded here.
#
# Example:
# LoadModule foo_module modules/mod_foo.so
#
# [...note that the modules include file has mod_rewrite listed as one of the modules to load]
Include conf.modules.d/*.conf

#
# If you wish httpd to run as a different user or group, you must run
# httpd as root initially and it will switch.
#
# User/Group: The name (or #number) of the user/group to run httpd as.
# It is usually good practice to create a dedicated user and group for
# running httpd, as with most system services.
#
User apache
Group apache

# 'Main' server configuration
#
# The directives in this section set up the values used by the 'main'
# server, which responds to any requests that aren't handled by a
# <VirtualHost> definition. These values also provide defaults for
# any <VirtualHost> containers you may define later in the file.
#
# All of these directives may appear inside <VirtualHost> containers,
# in which case these default settings will be overridden for the
# virtual host being defined.
#

#
# ServerAdmin: Your address, where problems with the server should be
# e-mailed. This address appears on some server-generated pages, such
# as error documents. e.g. admin@your-domain.com
#
ServerAdmin root@localhost

#
# ServerName gives the name and port that the server uses to identify itself.
# This can often be determined automatically, but we recommend you specify
# it explicitly to prevent problems during startup.
#
# If your host doesn't have a registered DNS name, enter its IP address here.
#
ServerName http://hostname.edu:80

#
# Deny access to the entirety of your server's filesystem. You must
# explicitly permit access to web content directories in other
# <Directory> blocks below.
#
<Directory />
AllowOverride none
Require all denied
</Directory>

#
# Note that from this point forward you must specifically allow
# particular features to be enabled - so if something's not working as
# you might expect, make sure that you have specifically enabled it
# below.
#

#
# DocumentRoot: The directory out of which you will serve your
# documents. By default, all requests are taken from this directory, but
# symbolic links and aliases may be used to point to other locations.
#
DocumentRoot "/var/www/html"

#
# Relax access to content within /var/www.
#
<Directory "/var/www">
AllowOverride All
# Allow open access:
Require all granted
</Directory>

# Further relax access to the default document root:
<Directory "/var/www/html">
#
# Possible values for the Options directive are "None", "All",
# or any combination of:
# Indexes Includes FollowSymLinks SymLinksifOwnerMatch ExecCGI MultiViews
#
# Note that "MultiViews" must be named *explicitly* --- "Options All"
# doesn't give it to you.
#
# The Options directive is both complicated and important. Please see
# http://httpd.apache.org/docs/2.4/mod/core.html#options
# for more information.
#
Options Indexes FollowSymLinks

#
# AllowOverride controls what directives may be placed in .htaccess files.
# It can be "All", "None", or any combination of the keywords:
# Options FileInfo AuthConfig Limit
#
AllowOverride All

#
# Controls who can get stuff from this server.
#
Order allow,deny
Allow from all
</Directory>

#
# DirectoryIndex: sets the file that Apache will serve if a directory
# is requested.
#
<IfModule dir_module>
DirectoryIndex index.html
</IfModule>

#
# The following lines prevent .htaccess and .htpasswd files from being
# viewed by Web clients.
#
<Files ".ht*">
Require all denied
</Files>

#
# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a <VirtualHost>
# container, error messages relating to that virtual host will be
# logged here. If you *do* define an error logfile for a <VirtualHost>
# container, that host's errors will be logged there and not here.
#
ErrorLog "logs/error_log"

#
# LogLevel: Control the number of messages logged to the error_log.
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
#
LogLevel warn

<IfModule log_config_module>
#
# The following directives define some format nicknames for use with
# a CustomLog directive (see below).
#
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common

<IfModule logio_module>
# You need to enable mod_logio.c to use %I and %O
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
</IfModule>

#
# The location and format of the access logfile (Common Logfile Format).
# If you do not define any access logfiles within a <VirtualHost>
# container, they will be logged here. Contrariwise, if you *do*
# define per-<VirtualHost> access logfiles, transactions will be
# logged therein and *not* in this file.
#
#CustomLog "logs/access_log" common

#
# If you prefer a logfile with access, agent, and referer information
# (Combined Logfile Format) you can use the following directive.
#
CustomLog "logs/access_log" combined
</IfModule>

<IfModule alias_module>
#
# Redirect: Allows you to tell clients about documents that used to
# exist in your server's namespace, but do not anymore. The client
# will make a new request for the document at its new location.
# Example:
# Redirect permanent /foo http://www.example.com/bar

#
# Alias: Maps web paths into filesystem paths and is used to
# access content that does not live under the DocumentRoot.
# Example:
# Alias /webpath /full/filesystem/path
#
# If you include a trailing / on /webpath then the server will
# require it to be present in the URL. You will also likely
# need to provide a <Directory> section to allow access to
# the filesystem path.

#
# ScriptAlias: This controls which directories contain server scripts.
# ScriptAliases are essentially the same as Aliases, except that
# documents in the target directory are treated as applications and
# run by the server when requested rather than as documents sent to the
# client. The same rules about trailing "/" apply to ScriptAlias
# directives as to Alias.
#
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"

</IfModule>

#
# "/var/www/cgi-bin" should be changed to whatever your ScriptAliased
# CGI directory exists, if you have that configured.
#
<Directory "/var/www/cgi-bin">
AllowOverride None
Options None
Require all granted
</Directory>

<IfModule mime_module>
#
# TypesConfig points to the file containing the list of mappings from
# filename extension to MIME-type.
#
TypesConfig /etc/mime.types

#
# AddType allows you to add to or override the MIME configuration
# file specified in TypesConfig for specific file types.
#
#AddType application/x-gzip .tgz
#
# AddEncoding allows you to have certain browsers uncompress
# information on the fly. Note: Not all browsers support this.
#
#AddEncoding x-compress .Z
#AddEncoding x-gzip .gz .tgz
#
# If the AddEncoding directives above are commented-out, then you
# probably should define those extensions to indicate media types:
#
AddType application/x-compress .Z
AddType application/x-gzip .gz .tgz

#
# AddHandler allows you to map certain file extensions to "handlers":
# actions unrelated to filetype. These can be either built into the server
# or added with the Action directive (see below)
#
# To use CGI scripts outside of ScriptAliased directories:
# (You will also need to add "ExecCGI" to the "Options" directive.)
#
#AddHandler cgi-script .cgi

# For type maps (negotiated resources):
#AddHandler type-map var

#
# Filters allow you to process content before it is sent to the client.
#
# To parse .shtml files for server-side includes (SSI):
# (You will also need to add "Includes" to the "Options" directive.)
#
AddType text/html .shtml
AddOutputFilter INCLUDES .shtml
</IfModule>

#
# Specify a default charset for all content served; this enables
# interpretation of all content as UTF-8 by default. To use the
# default browser choice (ISO-8859-1), or to allow the META tags
# in HTML content to override this choice, comment out this
# directive:
#
AddDefaultCharset UTF-8

<IfModule mime_magic_module>
#
# The mod_mime_magic module allows the server to use various hints from the
# contents of the file itself to determine its type. The MIMEMagicFile
# directive tells the module where the hint definitions are located.
#
MIMEMagicFile conf/magic
</IfModule>

#
# Customizable error responses come in three flavors:
# 1) plain text 2) local redirects 3) external redirects
#
# Some examples:
#ErrorDocument 500 "The server made a boo boo."
#ErrorDocument 404 /missing.html
#ErrorDocument 404 "/cgi-bin/missing_handler.pl"
#ErrorDocument 402 http://www.example.com/subscription_info.html
#

#
# EnableMMAP and EnableSendfile: On systems that support it,
# memory-mapping or the sendfile syscall may be used to deliver
# files. This usually improves server performance, but must
# be turned off when serving from networked-mounted
# filesystems or if support for these functions is otherwise
# broken on your system.
# Defaults if commented: EnableMMAP On, EnableSendfile Off
#
#EnableMMAP off
EnableSendfile on

# Supplemental configuration
#
# Load config files in the "/etc/httpd/conf.d" directory, if any.
IncludeOptional conf.d/*.conf

What's the output of ls -l /var/www/html/omeka-2.3/files ?

right now it looks like this: (I opened it up to chmod 777 just to see if that made any difference)

ls -l /var/www/html/omeka-2.3/files/
total 0
drwxrwxrwx. 2 apache apache 23 Mar 19 17:02 fullsize
drwxrwxrwx. 2 apache apache 23 Mar 19 17:02 original
drwxrwxrwx. 2 apache apache 23 Mar 19 17:02 square_thumbnails
drwxrwxrwx. 2 apache apache 23 Mar 19 17:02 theme_uploads
drwxrwxrwx. 2 apache apache 23 Mar 19 17:02 thumbnails

Okay. Those dots after the "rwx" strings indicate these files have an SELinux security context set on them, and that could easily be the problem here.

What do you get if you run the same command but ls -Z instead of ls -l?

Wow. Learned something new today! SELinux eh?

So here's the output - I've tried changing the labels a few ways to no success yet and put it back the way I found it.

[root@hostname omeka-2.3]# ls -Z
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 admin
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 application
-rw-r--r--. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 bootstrap.php
-rw-r--r--. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 db.ini
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 files
-rw-r--r--. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 index.php
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 install
-rw-r--r--. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 license.txt
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 plugins
-rw-r--r--. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 README.md
-rw-r--r--. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 robots.txt
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 themes

The specific command should have been ls -Z /var/www/html/omeka-2.3/files/

It's the info about the folders inside files that we're interested in here.

I'm not extremely familiar with SELinux, but you might need to set the type for files and its subdirectories to httpd_sys_rw_content_t (note the "rw") in this situation. You should be able to try that out with this command:

chcon -R -t httpd_sys_rw_content_t /var/www/html/omeka-2.3/files/

Ok, here's the result of ls -Z on files
[root@hostname omeka-2.3]# ls -Z files/
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 fullsize
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 original
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 square_thumbnails
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 theme_uploads
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 thumbnails

I ran the chcon as you suggested and check ls -Z again and the context is changed to the rw, however
after a server restart, checking via browser gets same permissions error and when I look at the audit log
it still says denied and the content_t context is still showing. Is there some other restart/refresh etc.
that needs done to apply that label?

[root@hostname omeka-2.3]# chcon -R -t httpd_sys_rw_content_t files/
[root@hostname omeka-2.3]# ls -Z files/
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_rw_content_t:s0 fullsize
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_rw_content_t:s0 original
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_rw_content_t:s0 square_thumbnails
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_rw_content_t:s0 theme_uploads
drwxrwxrwx. apache apache unconfined_u:object_r:httpd_sys_rw_content_t:s0 thumbnails
[root@hostname omeka-2.3]#
[root@hostname omeka-2.3]# service httpd restart
Redirecting to /bin/systemctl restart httpd.service
[root@hostname omeka-2.3]# tail /var/log/audit/audit.log
type=AVC msg=audit(1433944153.278:74081): avc: denied { write } for pid=18544
comm="httpd" name="thumbnails" dev="dm-0" ino=136518893 scontext=system_u:syste
m_r:httpd_t:s0 tcontext=unconfined_u:object_r:httpd_sys_content_t:s0 tclass=dir
type=SYSCALL msg=audit(1433944153.278:74081): arch=c000003e syscall=21 success=n
o exit=-13 a0=7f26ff207f58 a1=2 a2=0 a3=1 items=0 ppid=18541 pid=18544 auid=4294
967295 uid=48 gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none
) ses=4294967295 comm="httpd" exe="/usr/sbin/httpd" subj=system_u:system_r:httpd
_t:s0 key=(null)

ok, reboot :) that was the missing component.
Looks like I'm installing Omeka now. Thanks very much for your help!