CKA certification cluster troubleshooting questions

1. Very important things to remember. 

The string here and the path are very important. 
Always check the logs of kublet service. 

If the api server connection timeout then make sure that you are not missing anything in firewall. 
Make sure to check the logs to see the process is not complaining about it. Make sure path provides for all the configuration in config.yaml is correct and there is no syntax error. The logs will print details if there is any syntax error. 

[root@master ~]# cat /var/lib/kubelet/config.yaml | grep static
staticPodPath: /etc/kubernetes/manifests

2. POD and service DNS is not resolving in kubernetes.

Make sure that the busybox that you are trying to resolve it from is correct version. It should be following as per kubernetes doc.

kubectl apply -f https://k8s.io/examples/admin/dns/busybox.yaml

I was running older version of busybox that made pod DNS not working.

Pod DNS is:

10-3-3-3.<your_namespace>.pod.cluster.local

Service DNS is:

servicename.s<your_namespace>.svc.cluster.local

Raspberry Pi – how to setup Wifi WPA2-PSK

The configs below also set a manual IP at 192.168.1.60.

/etc/network/interfaces:

auto lo

iface lo inet loopback
iface eth0 inet dhcp

allow-hotplug wlan0
iface wlan0 inet manual
address 192.168.1.60 # change it to the static IP that you want.
netmask 255.255.255.0
gateway 192.168.1.1
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

/etc/wpa_supplicant/wpa_supplicant.conf:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
ssid="replace_with_your_ssid"
psk="replace_with_your_password"
proto=RSN
key_mgmt=WPA-PSK
pairwise=CCMP
group=CCMP
auth_alg=OPEN
}

Then I installed wicd and wicd-curses with the following commands:

sudo apt-get install wicd
sudo apt-get install wicd-curses

Run wicd-curses at the command line and setup your wireless network and let it automatically connect to this network on startup.

wicd-curses

-> Select wifi

-> C for config

-> Select the option to use this wi-fi at boot time to connect

-> C (Connect)

-> Save

Reboot and I was able to connect to my wireless network.

How to login kubernetes dashboard: K8s generate token

Connect to your kubernetes cluster.

 

kubectl -n kube-system get secret |grep kubernetes.io/service-account-token

#All secrets with type ‘kubernetes.io/service-account-token’ will allow to log in.

# Note that they have different privileges.

 

kubectl -n kube-system describe secrets aws-node-token-<WHATEVERSTRING>

 

You will get the token from the output. Use that for login

terraform : Error locking state: Error acquiring the state lock: ConditionalCheckFailedException: The conditional request failed

Error locking state: Error acquiring the state lock: ConditionalCheckFailedException: The conditional request failed
status code: 400, request id:

 

ID: 222Whatever-222Whatever-222Whatever-d86c-222Whatever
Path: terraform.tfstate
Operation: OperationTypePlan
Who: username@hostname
Version: 0.11.7
Created: 2018-09-27 15:02:22.226277904 +0000 UTC
Info:

 

Terraform acquires a state lock to protect the state from being written
by multiple users at the same time. Please resolve the issue above and try
again. For most commands, you can disable locking with the “-lock=false”
flag, but this is not recommended.

 

Fix:

terraform force-unlock 222Whatever-222Whatever-222Whatever-d86c-222Whatever . # this is the ID provided in Error message

How to move terraform state from one bucket to another?

From your existing config/s3 repo setup. Download the state with following command.

  1. terraform state pull > terraform.tfstate
  2. aws s3 cp –sse AES256 terraform.tfstate s3://Bucket_Name/Whatever_Path/terraform.tfstate
  3. Updated your backend config with new s3 location and change the profile for that account in your terrafrom config or backend config.
  4. Run terrafrom init

It will throw an error such as


Error loading state:
state data in S3 does not have the expected content.

This may be caused by unusually long delays in S3 processing a previous state
update. Please wait for a minute or two and try again. If this problem
persists, and neither S3 nor DynamoDB are experiencing an outage, you may need
to manually verify the remote state and update the Digest value stored in the
DynamoDB table to the following value: fe1212121Blah_Blah_Blah_1mduynend

Terraform failed to load the default state from the "s3" backend.
State migration cannot occur unless the state can be loaded. Backend
modification and state migration has been aborted. The state in both the
source and the destination remain unmodified. Please resolve the
above error and try again.

4. Go to your dynamoDB table config that you have setup in your AWS console for the table and LockID string. Search for the KEY that you have provided for LockID and change the value there with above mentioned fe1212121Blah_Blah_Blah_1mduynend value in last error.

5. Run terraform init again

 

This should move your S3 state from one bucket to new account’s bucket.

Gpg decryption error

While trying to decrypt the secrets in single line command line below I was getting error.


cat file <or echo "whatever">  | base64 --decode | gpg -d

gpg: public key decryption failed: Inappropriate ioctl for device
gpg: decryption failed: No secret key

The reason for the key that you have used is password protected. The pipe won’t work with gpg if your key is password protected.


gpg --export "Jayesh-key" | base64 # To get your key

gpg --list-keys

In order to get that working. Either you remove pipe in 2 commands.


echo "whatever" | base64 --decode > file.gpg

gpg -d file.gpg

or you can modify your key to be without password by providing blank password but thats not a recommended or ideal way.


gpg --edit-key YourKey

gpg prmpt > passwd

Once it prompts enter existing password to unlock. Once done just enter for blank password.

gpg prompt > save

Puppet Error 400 on SERVER: A duplicate resource was found while collecting exported resources, with the type and title Host

Even after clearing the certs from puppetmaster and client, if you are getting below error on your puppet client

Error 400 on SERVER: A duplicate resource was found while collecting exported resources, with the type and title Host

then its because you have messed up with certs badly.

Here is what you need to do.

Check the certs name from ls -al ${PUPPET_HOME}/ssl/ -R

once of the cert above has multiple hostname in it. Find all the hostname that comes as part of above command and delete all of them from puppet master.

once done clean the ssl folder from client

rm -rf ${PUPPET_HOME}/ssl/

and run the puppet agent.

Linux run script/service after few mins of reboot

You can use systemd timers to execute script a minute after boot.

First, create service file (/etc/systemd/system/myscript.service):

[Unit]
Description=MyScript

[Service]
Type=simple
ExecStart=/usr/local/bin/myscript

Then create timer (/etc/systemd/system/myscript.timer):

[Unit]
Description=Runs myscript every hour

[Timer]
# Time to wait after booting before activation
OnBootSec=1min
Unit=myscript.service

[Install]
WantedBy=multi-user.target
Now enable and run it:

# systemctl enable myscript.timer
# systemctl start myscript.timer

Eye strain: what to do?

While you are spending lots of your time. Make sure you are not putting too much of pressure on your eyes. Here is some tips.

These days your eyes can be put under a lot of strain for a number of reasons. Fortunately, there are a few things you can do to help relieve and even prevent eye strain so you’ll be able to keep using those babies for a long time.

Eight things you can do for eye health:

1) Get Plenty of Vitamin A
Your mother’s been telling you for years that if you eat carrots, it will increase your eyesight. This is absolutely true, but it isn’t just carrots you can eat–it’s anything with Vitamin A, which helps to safeguard against cataracts and macular degeneration. It also helps you to see better at night. Good food sources for Vitamin A include sweet potatoes, pumpkins, carrot juice, spinach, organ meats, kale, and turnip greens.

2) Take a Break
If you spend hours staring at a computer monitor or even a television every day, then taking a break will definitely help reduce eye strain. Try to spend no more than one hour without taking a break. Computer use results in a decrease of blinking to almost one third of normal, putting even more strain than usual on your eyes.

Note: If you have to stare at a screen for a long time, taking a break is one thing, but you should also look away from the monitor once about each ten minutes. There’s even software available to remind you.

3) Use Good Lighting
Avoid working in rooms that are dark or too dim. Using table lamps are better for your eyes than overhead lights. If you’re staring at a TV or monitor, make sure the light in the room is about equal to the brightness of the display. Movie theaters make up for this by having such a huge screen that their own light fills up the room.

4) Get Lots of Rest
Eyes need to sleep just like any other organ in your body. If your eyes are hurting or are bloodshot, you might need to get more sleep. At the very least, you can simply lay down and “rest your eyes” for a while.

5) Consider Using Reading Glasses
Even if you already wear prescription contacts, using reading glasses can help reduce eye strain. If you don’t wear glasses but have to struggle to read small text, if you use reading glasses not only will you be able to see small text more clearly, but you’ll also be able to sit further away from your computer monitor.

6) Do Eye Exercises
Close your eyes tightly for 5 seconds and then open them. Repeat 5 or 6 times. This will temporarily relieve strain and pressure. Lightly pressing a warm washcloth to your eyes once in a while is also a good idea. Don’t ever rub your eyes too hard, though, or you may break blood vessels.

7) Try Blackle
Viewing a dark screen is better than a bright, white screen. If you tend to use Google to search, try using Blackle instead (www.blackle.com). The search results are the same, plus as well as helping your eyes you also save energy.

9) Change the colour of your desktop/phone.
If you are using mac -> System Preferences -> Accessibiliy -> Display -> Check ” Invert colour. You can do the same by shortcut
Option + Command + N.
If you are using iphone -> Settings -> General -> Accessibility -> Display accomodation -> Invert Colors

9) Use ClearType
If you’re using Windows on your computer, try enabling ClearType font smoothing. (For Mac users, text smoothing is under the Appearance setting in your System Preferences.) This will help make reading type on your monitor much easier and put a little less strain on your eyes.