Ubuntu 18.04 is very new code, and there were some hacks to get PHP 5 and ODBC working properly with Asterisk and FreePBX. I'd stick with CentOS 6 if it were my call simply because it has a proven track record and is rock-solid reliable.
This past week I attempted two installs on CentOS (deets below). Both failed amusingly, so I am now trying it a third time on Ubuntu. Surely my error, or the fault of my VPS provider (our benchmark of excellence: CloudAtCost), but given those failures I'm trying Ubuntu 18.04 as I type this.
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Deets: I twice this week attempted to create a "newest-of-the-new" I-PBX installation on (yeah, yeah, but I have the resources lying around, they are working fine at the moment, its a sandbox to play in and I don't think it is the source of this problem) Cloud at Cost. I've done this many times over the years without issue. I used to always use CentOS. Then a few years back, because of difficulties getting a CentOS server spun-up on CaC I moved to Ubuntu. This time, because of difficulties upgrading the CaC-template Ubuntu 14.04 image to 18.04 (/boot is too small and runs out of room; have to fiddle with resizing partitions which I didn't initially want to do but now have done), I reverted to trying CentOS.
I created a base CentoOS server. It is installed as ver. 6.7. The first time I brought it up to 6.10 myself. The second time I let the I-PBX script ("yum -y update") make that happen. Fine and good: CentOS 6.10 was up and running.
I invoked the remaining parts of the script [see
http://nerdvittles.com/?p=23948 > Installing a Base CentOS Operating System > Installing Incredible PBX 13-13 LEAN > "Once you have CentOS up and running..."]. I ran the script [./IncrediblePBX-13-13.sh] and then ran it again. Automatic Update Utility ran. Status menu displayed, but showed Asterisk as down. I ran "/root/admin-pw-change" and "/root/timezone-setup."
Couldn't access the Incredible PBX 13-13 Web GUI -- nothing responded (500 error). Couldn't start/stop Amportal/Asterisk. 'Status' could not find the asterisk installation even though I thought I saw it properly installed in the flurry of compilation (I did notice the ascii-art "@" come up during the scroll).
So, the error happened exactly the same way, twice. I was going to seriously trouble-shoot the errors, but then I decided to just bite the bullet, blow-up that attempt (thus losing the logs), create a new Ubuntu server and re-partition the default CaC Dev1 template to give me the room that I needed to upgrade it to 18.04 (ultimately not terribly difficult. Shrank the swap partition by 200 MB and donated that to the /boot partition).