A Technical I.T./DevOps Blog
Problem scenario
You have a SATA hard drive. You want to copy data to a laptop via USB. What should you do?
Solution
Use a Vantec disk reader. (With IDE disk drives and Vantec disk readers for IDE drives, the disk reader can take 15 minutes before data is available.)
Question
You have heard the terms cognitive therapy, cognitive behavioral therapy, and behavioral therapy. What are the differences among these three things?
Answer
"If one were to view both behavior and cognitive therapies as opposite ends of a spectrum, then cognitive-behavioral theory is somewhere in between. " Taken from http://www.drkot.com/whatare.html
Cognitive therapy involves a professional listening and understanding the beliefs of a patient. It may involve the patient cultivating new opinions that are constructive and valid as certain maladaptive cognitions can harmful to the patient.
Cognitive behavioral therapy subsumes cognitive therapy. To learn about the differences between CT and CBT, see these two postings:
https://beckinstitute.org/does-cognitive-therapy-cognitive-behavior-therapy/
An example of CBT would be for a therapist to use caffeine wisely as opposed to excessively (pages 75 and 76 of Cognitive Behavioral Treatment of Insomnia).
Behavioral therapy involves modifying the environment. Behavioral therapy has nothing to do with changing attitudes to more valid, constructive beliefs. An example of behavioral therapy to treat insomnia would be to control the amount of stimulus received in the bedroom (taken from page 12 of Cognitive Behavioral Treatment of Insomnia).
For books that highlight iatrogenic effects of medicine or medical treatment, see these:
The Myth of Mental Illness: Foundations of a Theory of Personal Conduct Paperback – February 23, 2010 by Thomas S. Szasz (Author)
Medical Nemesis by Ivan Illich
"No small art is it to sleep: it is necessary for that purpose to keep awake all day." (Taken from page 36 of Thus Spake Zarathustra (Squid Classics 2017)).
Problem scenario
You are using Debian or Ubuntu Linux and you want to enter the PostgreSQL command prompt. What do you do?
Solution
Run these commands:
sudo su postgres
psql
You are done. Optionally you can run these passwords if you want:postgres=# create user jdoe with password 'goodpassword';
postgres=# create database foobar with OWNER=jdoe;
Problem scenario
You know Oracle VirtualBox on Linux has access to different network interfaces. The names of these NICs needs to be correct for some purpose of yours. How do you view or list this (for the purposes of creating a Vagrantfile)?
Solution
Run this command if you are running Unix/Linux: VBoxManage list bridgedifs
Problem scenario
You are using Debian or Ubuntu Linux and you want to enter the MySQL command prompt. What do you do?
Solution
Run this command: sudo mysql -u root
Problem scenario
You want to change the knock code itself or totally disable it on your Android tablet or phone. What do you do?
Solution
To remove the knock code:
Go to Settings -> Display -> Lock Screen -> Select screen lock
Enter the knock code and click "next".
Click on "None".
You are done.
To change the knock code:
Go to Settings -> Display -> Lock Screen -> Select screen lock
Enter the knock code and click "next".
Enter the knock code and click "Continue".
Repeat the above step.
You are done.
Problem scenario
You are using Debian or Ubuntu Linux and you want to install MySQL. What do you do?
Solutionsudo apt -y update
sudo apt -y install default-mysql-server mycli
sudo systemctl start mysql
Updated 11/9/17
Problem scenario
In AWS or Azure you have Linux instances that you want to be configured to use a Chef Server. How do you install Chef client and configure it to work with a Chef server?
Solution
These directions have been tested in Azure (with an Ubuntu 16.x server as either the Chef client node or the Chef server) and AWS (with a Red Hat Enterprise Linux 7.x server as the Chef client node or the Chef server). This solution will install Chef InSpec on RHEL 8.x
Prerequisite: This assumes you have access to the Chef Server and know where the organization permission file (e.g., orgname-validator.pem) is and user permission file (e.g., adminUser.pem) is. To set up Chef server, see this posting.
Procedures
1. From Chef client nodes you need the Chef server's URL to resolve without an IP address (i.e., you need an FQDN to route properly with TCP/IP operations). For the chef client servers, do one of two things:
a) Update the /etc/hosts file so the Chef server's FQDN maps to an IP address. For AWS this would normally be the internal IP address of the Chef server.
b) If you do not want to configure the /etc/hosts file you may configure your Chef client machine (server or computer) to use a DNS server so the FQDN of the Chef server will resolve correctly.
2. a) On the Chef client, create the directory "/etc/chef" (with no quotes).
b) This substep only applies if your Chef server is in AWS. (Your Chef client nodes could be on-premises or in Rackspace or Azure.) Ensure that the AWS Security Group governing the Chef server allows TCP connections from the IP address of the Chef client server. If the Chef client machine is also in AWS and will use an /etc/hosts file with the internal IP address of the Chef server, then the Security Group protecting the Chef server should allow for inbound connections from the internal IP address of the Chef client server. If the Chef client machine in AWS will map the FQDN of the Chef server to its external IP address or if the Chef client machine is not in AWS, use the external IP address of the Chef client for the Security Group inbound rule. Go directly to step 3 (and skip step 2.c).
c) This substep only applies if your Chef server is in Azure. (Your Chef client nodes could be on-premises or in Rackspace or AWS.) Ensure that the Network Security Group (NSG) for the Chef server allows TCP connections from the IP address of your workstation. (Use ipchicken.com if you need to.) You may be able to SSH into your Chef server, but by default the relevant NSG may restrict your ability to open a web UI connection from a web browser. For non-Azure Chef client servers, you should also ensure that the NSG in Azure that controls and protects the Chef server allows for inbound connections from the Chef client servers' external IP addresses.
3. From the server that will be configured as a Chef client, run this command:
sudo curl -L https://www.opscode.com/chef/install.sh | sudo bash
4. From the Chef client machine, do the following.
a) Create a client.rb file in /etc/chef/ with the following three lines:
chef_server_url 'https://<FQDN of Chef server>/organizations/contint'
validation_client_name 'contint-validator'
ssl_verify_mode :verify_none
b) Replace <FQDN of Chef Server> with the FQDN of the Chef server. Replace "contint" with your organization name. Replace "contint-validator" with the name of your validator file.
5. a) Open a web browser and go to the Chef server's URL or external IP address (e.g., http://<FQDN of Chef server>/organizations/nameOfOrganization). (The browser must accept cookies from this Chef's web UI.)
b) Go to Policy -> Clients.
c) Go to Create
d) Enter the FQDN of the Chef client server. (This can be found by using "hostname -f" on the Linux prompt of the Chef server.)
e) Click "Create Client."
f) Copy the text in the window that pops up. (Include "-----BEGIN RSA PRIVATE KEY-----" and everything beneath including the last line "----- END RSA PRIVATE KEY-----".)
g) Go to the Chef client's command interface (e.g., Linux prompt). Go to /etc/chef/ and create a file named client.pem. The contents should be the text from substep f above.
6. Run a command like this (but substitute the <FQDN of Chef Server> appropriately, and substitute "contintnick" with your organization's nickname):
sudo chef-client -S https://<FQDN of Chef Server>/organizations/contintnick
# The "contintnick" would be whatever you used on the Chef server when you ran this command where "companynickname" is:
sudo chef-server-ctl org-create companynickname 'Continual Integration' --association_user contint --filename contint-validator.pem
Problem scenario
You want to know about some common kubectl commands. What should you do?
Solution
The below was taken from running "kubectl help". Here are some kubectl commands:
Basic Commands (Beginner):
create Create a resource from a file or from stdin.
expose Take a replication controller, service, deployment or pod and expose it as a new Kubernetes Service
run Run a particular image on the cluster
set Set specific features on objects
Basic Commands (Intermediate):
explain Documentation of resources
get Display one or many resources
edit Edit a resource on the server
delete Delete resources by filenames, stdin, resources and names, or by resources and label selector
Deploy Commands:
rollout Manage the rollout of a resource
scale Set a new size for a Deployment, ReplicaSet, Replication Controller, or Job
autoscale Auto-scale a Deployment, ReplicaSet, or ReplicationController
Cluster Management Commands:
certificate Modify certificate resources.
cluster-info Display cluster info
top Display Resource (CPU/Memory/Storage) usage.
cordon Mark node as unschedulable
uncordon Mark node as schedulable
drain Drain node in preparation for maintenance
taint Update the taints on one or more nodes
Troubleshooting and Debugging Commands:
describe Show details of a specific resource or group of resources
logs Print the logs for a container in a pod
attach Attach to a running container
exec Execute a command in a container
port-forward Forward one or more local ports to a pod
proxy Run a proxy to the Kubernetes API server
cp Copy files and directories to and from containers.
auth Inspect authorization
Advanced Commands:
diff Diff live version against would-be applied version
apply Apply a configuration to a resource by filename or stdin
patch Update field(s) of a resource using strategic merge patch
replace Replace a resource by filename or stdin
wait Experimental: Wait for a specific condition on one or many resources.
convert Convert config files between different API versions
kustomize Build a kustomization target from a directory or a remote url.
Settings Commands:
label Update the labels on a resource
annotate Update the annotations on a resource
completion Output shell completion code for the specified shell (bash or zsh)
Other Commands:
api-resources Print the supported API resources on the server
api-versions Print the supported API versions on the server, in the form of "group/version"
config Modify kubeconfig files
plugin Provides utilities for interacting with plugins.
version Print the client and server version informationProblem scenario
You updated the Directory section of apache2.conf. You changed the DocumentRoot stanza in apache2.conf too. But when you browse to the website, you are not getting to the files in the directory you changed it to. You are getting files from /var/www/html/. Apache has been installed on Debian Linux. What do you do?
Solution