All – Page 225 – CONTINUAL INTEGRATION

How Do You Troubleshoot a C++ Program That Will Not Compile Due to Undefined Reference Errors?

03/19/201708/30/2019 0 Comments

Problem scenario: You try to compile a C++ program with gcc, but you get this output:

/tmp/ccj6eKDl.o: In function `main’:
q.cpp:(.text+0x14): undefined reference to `std::cout’
q.cpp:(.text+0x19): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)’
q.cpp:(.text+0x28): undefined reference to `std::cout’
q.cpp:(.text+0x2d): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)’
/tmp/ccj6eKDl.o: In function `__static_initialization_and_destruction_0(int,

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How Do You Troubleshoot Installing Oracle VirtualBox Guest Additions on a CentOS Server?

03/18/201701/20/2021 0 Comments

Problem scenario
You are running Oracle VirtualBox on a Windows host. You have Linux CentOS guest server. Guest additions fails to install. You tried to run this script VBoxLinuxAdditions.run. The run fails with an error saying “
check /var/log/VBoxGuestAdditions.log for details.”

You examined /var/log/VBoxGuestAdditions.log, and it said this:
“vboxadd.sh: failed: Look at /var/log/vboxadd-install.log to find out what went wrong.
vboxadd.sh: failed: Please check that you have gcc,

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How Do You Use PowerShell to Search Every Folder for a File by the File’s Name?

03/17/201708/30/2019 0 Comments

Problem scenario: You want to find a file on your Windows desktop by a specific name. How do you search every folder to find it?

Solution
Use PowerShell. Run these two commands to find “foobar.txt”:

cd /
gci -recurse -filter “foobar.txt”

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How Do You Permanently Change the Hostname of a Linux CentOS Server?

03/17/201708/23/2019 0 Comments

Problem scenario: You edited the /etc/hosts file and the /etc/sysconfig/network file to have a new hostname. You used the “hostname newHostname” command (where newHostname is the desired new host name). You rebooted the server and the hostname is still localhost.localdomain. How do you configure the host name to be different?

Solution
None of the above steps were necessary for changing the hostname for the purposes of having the “hostname” command return a new hostname.

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How Do You Find the Network Interface Name of a CentOS 7.X Server That Will Connect to the Default Gateway of Your Network?

03/17/201708/30/2019 0 Comments

Problem scenario: You want to find the name of the network interface that can connect to the default gateway on your Linux CentOS 7.x server. Typical new deployments of CentOS 7.x using the minimal .ISO do not have the “route” utility nor the “ifconfig” utility installed. How do you find the interface’s name (e.g., eth0) without using the “route” command?

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When Running Oracle VirtualBox on a Windows Host with a Linux Guest, What Does the Linux Guest Think Is the IP Address of the Host?

03/16/201701/20/2021 0 Comments

Problem scenario: You have Oracle VirtualBox installed on a Windows host. You have Linux CentOS as a guest VM. You want to test network connectivity (e.g., hostname resolution). You want to know what IP address the Linux guest could use to interact with the Windows host.

Solution
Install traceroute with this command:

sudo yum -y install traceroute

Then use this command:

traceroute 8.8.8.8

The results of the above traceroute command will show you the packet hop from the Linux guest to the Windows host.

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How Do You Install Docker on an AWS Instance of RHEL?

03/15/201702/14/2022 0 Comments

UPDATE: If you are using RHEL 8.x use these directions instead of the ones below.

Problem scenario
You want to install Docker on an AWS instance of RedHat Linux (version 7.x or below). You do not want to use CentOS packages. What do you do?

Solution
For RedHat Linux running via AWS, you have to run one command to enable numerous yum repositories.

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How Do You Configure Updates for a RedHat Server Running on AWS?

03/14/201705/29/2019 0 Comments

Question: How Do You Get Yum Repositories to Work with a AWS Instance of RHEL?
Problem scenario: You are using RedHat Linux via AWS and very few yum commands work. The repositories are very limited, and few packages are available. When trying to use yum to install packages, you see output like this:

“Loaded plugins: amazon-id, rhui-lb
…
No package lynx available.

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How Do You Troubleshoot Yum Commands Not Working with the Error “Could Not Resolve Host: mirror.centos.org Unknown Error”?

03/14/201708/23/2019 0 Comments

Problem scenario: Yum commands to install packages are not working. When you use “yum install coolpackage” you get an error like this:

‘
http://mirror.centos.org/altarch/7/os/i386/repodata/repomd.xml: [Errno 14] curl#6 – “Could not resolve host: mirror.centos.org; Unknown error”
Trying other mirror.
https://yum.dockerproject.org/repo/main/centos/7/repodata/repomd.xml: [Errno 14] curl#6 – “Could not resolve host: yum.dockerproject.org; Unknown error”
Trying other mirror.

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One of the configured repositories failed (Docker Repository),

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