Tag Archives: ssh

How to recover access to your Amazon AWS EC2 instance if you loss your Private Key for SSH

This article covers the desperate situation where you had generated one or more instances, instructed Amazon to use a SSH Key Pair certs where only you have the Private Key, your instances are running, for example, an eCommerce site, running for months, and then you loss your Private Key (.pem file), and with it the SSH access to your instances’ Data.

Actually I’ve seen this situation happening several times, in actual companies. Mainly Start ups. And I solved it for them.

Assuming that you didn’t have a secondary method to access, which is another combination of username/password or other user/KeyPairs, and so you completely lost the access to the Database, the Webservers, etc… I’m going to show you how to recover the data.

For this article I will consider an scenario where there is only one Instance, which contains everything for your eCommerce: Webserver, code, and Database… and is a simple config, with a single persistent drive.

Warning: be very careful as if you use ephemeral drives, contents will be lost is you power off the instance.

Method 1: Quicker, launching a new instance from the previous

Step1: The first step you will take is to close the access from outside, using the Firewall, to avoid any new changes going to the disk. You can allow access to the instance only from your static Ip in the office/home.

Step 2: You’ll wait for 5 minutes to allow any transaction going on to conclude, and pending writes to be flushed to disk.

Step 3: From Amazon AWS Console, EC2, you’ll request an Snapshot. That step is to try to get extra security. Taking an Snapshot from a live, mounted, filesystem, is not the best of ideas, specially of a Database, but we are facing a desperate situation so we’re increasing the numbers of leaving this situation without Data loss. This is just for extra security and if everything goes well at the end you will not need this snapshot.

Make sure you select No reboot.

Step 4: Be very careful if you have extra drives and ephemeral drives.

Step 5: Wait till the Snapshot completes.

Step 6: Then request a graceful poweroff. Amazon will try to poweroff the Server in a gentle way. This may take two minutes.

Step 7: When the instance is powered off, request a new Snapshot. This is the one we really want. The other was just to be more safe. If you feel confident you can just unclick No Reboot on the previous Step and do only one Snapshot.

Step 8: Wait till the Snapshot completes.

Step 9: Generate and upload the new key you will use to AWS Console, or ask Amazon to generate a key pair for you. You can do it while creating the new instance through the wizard.

Step 10: Launch a new instance, based on your snapshot AMI. This will generate a copy of your previous instance (using the Snapshot) for the new one. Select the new Key pair. Finish assigning the Security groups, the elastic ip…

Step 11: Start the new instance. You can select a different flavor, like a more powerful instance, if you prefer. (scale vertically)

Step 12: Test your access by login via SSH with the new pair keys and from your static Ip which has access in the Firewall.

ssh -i /home/carles/Desktop/Data/keys/carles-ecommerce.pem ubuntu@54.208.225.14

Step 13: Check that the web Starts correctly, check the Database logs to see if there is any corruption. Should not have any if graceful shutdown went well.

Step 14: Reopen the access from the Firewall, so the world can connect to your instance.

Method 2: Slower, access the Data and rebuild whatever you need

The second method is exactly the same until Step 6 included.

Step 7: After this, you will create a new instance based on your favorite OS, with a new pair of Keys.

Step 8: You’ll detach the Volume from the eCommerce previous instance (the one you lost access).

Step 9: You’ll attach the Volume to the new instance.

Step 10: You’ll have access to the Data from the previous instance in the new volume. type cat /proc/partitions or df -h to see the mountpoints available. You can then download or backup, or install the Software again and import the Database…

Step 11: Check that everything works, and enable the access worldwide to the Web in the Firewall (Security Group Inbound Rules).

If you are confident enough, you can use this method to upgrade the OS or base Software of your instance, making it part of your maintenance window. For example, to get the last version of Ubuntu or CentOS, MySQL, Python or PHP, etc…

Troubleshooting a shell prompt irresponsible that locks/hangs intermittently

You do df -h or ls / and the terminal freezes and not even CTRL + C works, you have a lock.

Normally this is due to a lock of the system trying to perform an IO.

Could be a physical spinning disk failing, but the most probably nowadays is that you have a network mount point and it is timing out.

If you execute mount and you get a timeout, and when you finally see the list you see a NFS, iSCSI or another kind of Network mount (you will see an Ip Address), check for errors.

To do this in CentOS/RHEL you can do as root:

dmesg | grep -i "timed"

or depending on the System

cat /var/log/messages | grep -i "timed"

You’ll get something like this:

[root@compute01 carles]# dmesg -T | grep timed | head -n5
[Fri Mar 20 02:27:44 2020] nfs: server storage07 not responding, timed out
[Fri Mar 20 02:27:44 2020] nfs: server storage07 not responding, timed out
[Fri Mar 20 02:27:44 2020] nfs: server storage07 not responding, timed out
[Fri Mar 20 02:27:44 2020] nfs: server storage07 not responding, timed out
[Fri Mar 20 02:27:45 2020] nfs: server storage07 not responding, timed out

Please note I use dmesg -T in order to have human readable date instead of Unix Epoch.

You can count the errors today:

[root@compute01 carles]# dmesg -T | grep time | grep "Mon Apr 6" | wc --lines
3123

Raspberry Pi and osmc

RaspberryPiB+There is something that fascinates me from the new Raspberry Pi, and using it as a media center.
It is the fact that is a really small board.
That is powered by a micro USB 1000 mhA.
That is powered with Linux.

I had other media centers before but they were magnetic hard disk, closed in a proprietary system.
The media center I installed, with RaspBerry Pi+, is osmc, that is Open Source Media Center.

blog-carlesmateo-com-raspberry-pi-2-osmc-ssh-topSo I have full access via ssh to the RaspBerry, and as it used so few energy I have it all the day up.
Then, as it is a Linux box, and I have full access, and I’ve around 546 MB RAM free, I can run as many background process as I want.
Do I want to be a jump point for my VPN? Let’s go.
Do I want to have some monitoring processes over few websites? Let’s do it!.

I’m really happy about having a so tiny, so few energy consuming, full Linux, being my media center and whatever I want to it to do.

I must say that is wonderful having SSH and a network interface. Ok, it’s 10/100 Mbps, not Gigabit, but it is enough to allow me to copy new files in background to the USB stick via SFTP while reproducing at FullHD Blueray MKV, files right. Also allows to mount network folders via NFS or SMB amd play from them. Copying via SFTP to the USB device is generally very slow -don’t be surprised to upload at 30 KB/s- so I recommend to set a NFS folder in the computer, with read access to the ip of the Raspberry. It’s very cool and plays totally smooth using the 100 Mbit ethernet connection. You can also configure a FTP in the Pi, that will be much faster than the SFTP.

The RaspBerry micro SD card has a performance of ~22 MB, that is enough to boot very quickly and to load programs quite fast. I have other microSD cards with Debian Jessie, and I load PHPStorm (Java based PHP IDE) quite fast.

It boots really fast, in case you stop and start it frequently.

It accepts my wired Mouse and Keyboard, and also wireless bluetooth.

I’m really in love with this small motherboard. :)

This tiny RaspBerry 2, has 4 cores at 900 Mhz.

The CPU announces (cat /proc/cpuinfo):

processor    : 3
model name    : ARMv7 Processor rev 5 (v7l)
BogoMIPS    : 38.40
Features    : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm
CPU implementer    : 0x41
CPU architecture: 7
CPU variant    : 0x0
CPU part    : 0xc07
CPU revision    : 5

As you see, it scores only 38.40 bogomips, compared to my tower desktop 6384.59, and my old laptop 2593.45, but it’s still beautiful.

Note: you cannot trust bogomips as a performance measurement, and in addition my computers are Intel based -so CISC architecture- while RasbBerry uses ARM processors that are RISC, that is a completely different architecture. I notice a very fluid speed, only I sense a bit slowliness in the process when I install new packages. When unpacking it feels slow, although it can perfectly be caused by the SSD card IO as well, so I installed iotop and monitorized the I/O while I was installing PHP5 :) . I got small writings up to 1,000 KB/sec, so 1 MB/s, with average of ~30-50KB writing operations, no iowait, while I was seeing with htop that the core unpacking was at 100 % of CPU, the other 3 were free, so my initial conclusion is that the bottleneck was on the CPU. Still happy about my little gadget. :)

The osmc image I installed comes with python 2.7.9 and Linux kernel 3.18.9 as uname -a shows:

Linux osmc 3.18.9-5-osmc #1 SMP PREEMPT Wed Mar 11 18:59:35 UTC 2015 armv7l GNU/Linux

It also comes with wget 1.16 and curl 7.38.0.

In fact the OSMC is based on the Debian Jessie distro.

The OSMC software also have upgrades, and Debian upgrades, that keep the Linux box up to date.

So that brings a lot of possibilities.

After a sudo apt-get update I was able to install htop, mc and apache2.

sudo apt-get install htop
sudo apt-get install iotop
sudo apt-get install iftop
sudo apt-get install mc
sudo apt-get install apache2
sudo apt-get install php5
sudo apt-get instlal ncdu

So it’s a lot of fun. :)

Note: Although a 1000mhA is enough (Raspberry Pi 2 needs around 700mhA) if you plan to plug a cheap case 2.5 hard disk without external power -just USB- it will not be enough. In this case I recommend buying a 2000mhA transformer for the Pi, or a external USB hub energy powered (2000mhA otherwise you risk energy from Raspbery + USB hub being to sufficient). If the disk has external power, then you’ll have no probem. Personaly I use USB sticks.

When I had my incubator of Start ups some years ago, one of my Start up project was embedding motherboards within screens, and offering the ability to play videos, images, even flash games and animations, and manage and update everything and update contents for a groups of players from the Internet, or based on time triggers. I was finalist for selling my product to a enormous multinational, it was close, but finally a Korean company with a cheaper (and less powerful solution) won. At that time, it was 2004, motherboards were huge comparing to this tiny piece of hardware and I had to deal with different voltage, power consumption, heat dissipation, safety, etc…. so I’m really in love with this tiny piece hardware that doesn’t need even a ventilator or a big dissipation mechanism.