All ports blocked, ping works, firewall and apparmor off

[Brian Poissant]

Maybe it's a protocol problem given that point works (ICMP) and everything
else doesn't (TCP/UDP).
On Apr 10, 2015 5:52 AM, "Tony Baechler - BATS" <bats at batsupport.com> wrote:

> Hi all,
>
> I've been struggling with this for days and am getting nowhere.  I'm
> totally
> baffled and have tried everything I can think of, including several Google
> searches.  I am sorry for the lack of information, but I'm not sure what to
> post as I've never seen anything like this before.
>
> I'm running a Ubuntu 14.04.1 server.  It has ssh, Postfix, Apache2, etc.  I
> upgraded from kernel 3.13.04-6-generic to 3.13.04-8-generic and rebooted.
> Everything was working fine, but I couldn't connect after the reboot.  I
> tried nmap and it says all ports are closed.  My first thought is that it
> must be a firewall, so I completely purged ufw and iptables but no luck.  I
> restored /etc/network/interfaces from a known good backup.
>
> After reading various forum posts, I again installed iptables and copied
> and
> pasted the script from the official Ubuntu wiki to disable the firewall,
> just in case old rules were left.  That should allow all incoming and
> outgoing traffic.  Apparently the script works as pinging works fine even
> though nmap says all ports are closed.  I've tried rebooting several times
> just in case.  I ran e2fsck and my disks are clean.  I am able to boot into
> a separate rescue system, so it's definitely not an obvious hardware
> problem.  I also ran update-grub and update-initramfs just in case.
> Finally, I reconfigured grub-pc and installed the bootloader on both
> /dev/sda and /dev/sdb.  I'm running software RAID and I didn't install it
> on
> /dev/md1, but I don't think that would matter.  I have to access the server
> remotely and writing to their support was of no help.
>
> What's really strange is that it boots fine with kvm from the rescue
> system.
>  I can get to the login prompt and everything seems to be fine.  It acts
> like a boot problem, but I don't see why ping would work if it isn't
> booting.  Nothing gets written to syslog, so it acts like it's an init
> problem, but I didn't change anything that I know of and I saw no errors
> with kvm.  Without kvm, it doesn't seem to boot as I mentioned.  Just in
> case, I removed or purged qemu, ufw, iptables, apparmor, etc.  I also tried
> upgrading to a completely different kernel, specifically
> 3.16.0-33-lowlatency.  It's an Intel x86-64 processor with 32 GB of RAM.
> It
> did work fine after the initial install.  According to mdadm, my RAID
> arrays
> are fine.
>
> Again, I've tried everything that comes to mind but I'm out of ideas.  I
> don't want to do a fresh install, but I don't know what else to do.  I can
> post more specific information, but I don't know what would help.  I've
> gone
> through everything which seems relevant and mostly things are still at the
> defaults.  There are no wireless devices or other network interfaces except
> eth0 and there shouldn't be a firewall issue.  Does anyone here have any
> ideas?  Please help!  Thank you.
>
>
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