A Technical I.T./DevOps Blog
Problem scenario
You are using Windows 7 and PowerShell version 3. You want to test if a port is open to a given IP address. (If you are using a modern version of PowerShell, use the Test-NetConnection command.) How do you find out if a port of an IP address is open or not?
Solution
Use the PowerShell function Test-TCPPortConnection written by Jonathan Medd. Every line of this code except the last line was taken from here.
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Problem scenario
You want your central Jenkins 1.651.1 server running on Linux to push down builds (or run jobs) on Windows servers. When you try to connect Jenkins master to a slave server, you get an error message like this:
“ERROR: Access is denied. See http://wiki.jenkins-ci.org/display/JENKINS/Windows+slaves+fail+to+start+via+DCOM for more information about how to resolve this. org.jinterop.dcom.common.JIException: Message not found for errorCode: 0x00000005 at org.jinterop.dcom.core.JIComServer.init(JIComServer.java:”
You know the credentials and IP address are correct.
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Continue reading “How Do You Get Jenkins Running on Linux to Work With Windows Servers?”
Problem scenario: You run this command on a Linux CentOS server:
sudo mount -t cifs -o user=jdoe //172.33.44.55/contintshare /mnt/windows-share
But you get this error: “mount: wrong fs type, bad option, bad superblock on //172.33.44.55/contintshare, missing codepage or helper program, or other error (for several file systems (e.g., nfs, cifs) you might need a /sbin/mount.<type> helper program)”
What do you do?
Solution
The error message is not clear or helpful.
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Problem scenario: How do you use the grep command to recursively search most subdirectories (excluding some directories) for a pattern? You want to find a file with a string like this:
/var/lib/pgsql/data
You are not interested in the files in directory paths that have one or more parent (or any antecedent) directories named “proc” nor “sys”. You want to list files that have the above pattern.
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Problem scenario: You have Oracle VirtualBox running on a Windows 7 computer as the host. You have a Linux CentOS guest supported by Oracle VirtualBox. You want to have a file share that does not rely on vboxsf. What do you do?
Solution
1. On the Windows host desktop, create a folder. For this example, we’ll use “foobar” for the name.
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Problem scenario:
You created a new Linux CentOS 7.x guest server using Oracle VirtualBox on a Windows host. Your Windows machine has Internet access. From the Linux Guest you try to ping a 8.8.8.8 but you get this message “connect: Network is unreachable.”
How do you give the Linux guest Internet access?
Possible Solution #1
1. Using the GUI of the Oracle VirtualBox guest server,
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Problem scenario: You have a Linux Centos 7.3 server. You want to get Postgresql to work on it. What do you do?
Solution
To get Postgresql working on a CentOS 7.3 server, do the following four commands as the root user:
yum -y install postgresql-server postgresql-contrib
postgresql-setup initdb
systemctl start postgresql
systemctl enable postgresql
# To issue SQL commands,
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Continue reading “How Do You Install and Configure Postgresql on a Linux CentOS 7 Server?”
Problem scenarios: Either you are using CentOS 7.x (and ifconfig is even not a command) or you are using ifconfig and different flags (like -v for verbose), but you cannot find the default gateway. How do you know if you have a default gateway even configured on a Linux server?
Solution The “ifconfig” command cannot show the default gateway. To find the default gateway on your Linux server,
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Continue reading “How Do You Find The Default Gateway of Your Linux Server?”
Problem scenario: You are using knife commands and getting errors. For example, you try to run this: knife client list
As a result, you get this error:
“WARN: Failed to read the private key /root/.chef/continual.pem: #<Errno::ENOENT: No such file or directory @ rb_sysopen – /root/.chef/continual.pem>
ERROR: Your private key could not be loaded from /root/.chef/continual.pem
Check your configuration file and ensure that your private key is readable”
What should you do?
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Problem scenario: How do you find out what version of PowerShell you are using?
Solution
Run this command: $PSVersionTable.PSVersion
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Continue reading “How Do You Determine the Version of PowerShell That You Are Using?”