ec2 is not pingable but not same case in previous - amazon-ec2

I'm having ec2 machine in AWS, and it was pingable from till last night 6 Pm and suddenly it was not pingable. I googled and suggested add rule in security group.
I would like to know the reason why it was worked and why its stopped working suddenly?
Can someone let me know the reason?

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SCCM PXE not getting IP address

Our organization uses SCCM 2016 connected to two MS Server 2016-based DPs. The first works fine though the other recently (last 30 days or so) stopped communicating with the PXE. We don't know what exactly caused this (perhaps a CU update?). Essentially, when pressing F12 to start PXE, we don't get any IP address.
The process goes as follows:
>>Checking Media Presence......
>>Media Present.......
>>Start PXE Over IPv4 (MAC address)
In attempt to get it to work, I have restarted the DHCP server and set up a new DP, the problem persists.
Our servers are up-to-date with the latest Microsoft update (which at this point we would not like to revert due to security reasons). What would you guys suggest me do?
Thanks in advance!
Make sure you have configured DHCP Options 66 and 67 on the scope where you attempt to boot to PXE.
Since it looks like you attempt to boot from UEFI, it will be better for you to setup a DHCP Policy to direct UEFI and BIOS clients to the correct file each time. Here's a great tutorial for setting this up

AWS Cloud9: Environment Stops Responding

I trying to setup AWS Cloud9 and am running into a wall each time I try to setup my environments. Once I create the environment and start following this guide https://docs.aws.amazon.com/cloud9/latest/user-guide/sample-lamp.html to configure the LAMP server, through the Cloud9 IDE terminal, the environment will just stop responding. Once I try to reload the IDE I get the follow error;
Cannot connect to instance error message.
Rebooting the instance doesn't seem to resolve the error message. But any time I make a fresh instance it will let me work from anywhere to 30 seconds to 90 seconds before it stops responding.
I have looked through my VPC port settings, as well as security group settings, and they both appear to the correct.
VPC inbound rules VPC outbound rules Security Group inbound
rules Security Group outbound rules
Additionally, I was using the default t2.micro instance until I read this post AWS Cloud9: Cannot open environment and have tried with the t2.small but I am still getting the same results.
Any help with where else to look or what else to try would be much appreciated!
Edit: It appears to be random when it stops and freezes, for example when making a m4.large instance. It froze while I was setting up the sudo mysql_secure_installation.
Once I typed "Y" it wouldn't let me press enter. Reloading the IDE gave me the VPC error.
Welcome to SO! When I use cloud9 I tend to use m4.large for anything that's non-trivial. If you're running Apache and MySQL on the same host I would definitely try the m4.large instance. It's $0.10/hr (pricing) so you could try it out fairly cheaply. I'm guessing that's the root of the issue. If you're still having the issue please repost here and we can check further.
Just to confirm:
- You can connect to the instance at least once (even if for a few seconds)
- You see the IDE and can type for 30-60 seconds before it stops responding
If you can't connect that's likely a different issue.

Opening Realm Dashboard on Amazon EC2

I'm trying to setup Realm Object Server on Amazon EC2.
I've used the public AMI on North Virginia, and I have a running instance. I'm doing all this from Europe as most of my users are in the USA.
Now I'm trying to access ec2-xx-xx-xx-xx.compute-1.amazonaws.com:9080.
I've tried to open the different ports as indicated but I feel that what I've done is incorrect.
I've also tried to open all traffic but I still have a timeout on the page. I'm probably doing something wrong here, I'm not sure what.
Thanks for your help!
Thanks for trying out our AWS AMI! It would be helpful to know the AMI ID that you ran, as that can help us track down problems for others. In fact, we've released new AMIs this morning. Check our website for the latest available AMI IDs.
In the meantime, can you check if the realm-object-server service is running? You can check this via SSH and by running:
sudo service realm-object-server status
So I managed to make things work!
I guess my issue is that I was somehow on the wrong security group.
When looking at your running instances, be sure to hit your security group at the right of the instance row, in order to be able to configure the correct one.
Then, configure a Custom TCP Rule with port 9080.
That's it!

AWS EC2 Ubuntu 14.04 Keeps Timing Out

I've spun up and setup 2 servers now in this AZ and both keep going down shortly after being used. Restarting doesn't fix it and I have to start and stop them.
By going down I mean a timeout error for apache and I can't even SSH. Port 22 is open and I can SSH in once I stop and start the EC2, it doens't run out of memory and only has 2 sites on a t2.medium with the database on RDS.
One of the sites is https://coffeehive.com.au/ if that helps
Any ideas?
Cheers,
Adrian

DataStax Enterprise AMI hangs during installation

I booted the DataStax AMI for Amazon EC2, logged in via SSH, but the terminal hangs on "Installation Started":
Cluster started with these options:
--clustername CassandraDev --totalnodes 1 --version enterprise --username **** --password ****
Installation started.
"Installation started" keeps going through suffixes consisting of one, two, and three dots. But nothing happens, I can't quit the installation process, and I can't access any log files to see what might be going on (or I don't know how).
Tried on two separate m3.large instances operating in a VPC subnet, at the us-east-1 region. The exact AMI is datastax_clustering_ami_2.5.1_hvm.manifest.xml (ami-ada2b6c4). On the first instance, I waited about an hour and a half. The second instance I just left online all night, with the same results.
Because this is a VPC, all outbound traffic goes through a NAT server. Security groups allow outbound traffic only on ports 80, 443, and 123. Might there be another outbound port that needs to be opened? Inbound ports do not matter, as the server is not public-facing, but within the subnet I have allowed all traffic on all ports.
Someone else has had a similar issue, but without answers so far: DataStax AMI hangs on
Any help would be appreciated!
Since there were a few tickets that came up recently around the same issue, it seems as though something recently changed within the AMI provisioning side in EC2, or this specific configuration of VPCs had never been used before, which seems a bit unlikely.
The current fix is to add an additional entry into /etc/hostname to get rid of the stderr output that occurs after each sudo command. This in turn doesn't get flagged as an error on the provisioning side.
This has been fixed and patched as documented on this ticket:
https://github.com/riptano/ComboAMI/issues/51.
If you spot any additional issues, feel free to create another ticket there.
Going forward, just launch another set of instances using the same user-data and you should be up and running.

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