A Technical I.T./DevOps Blog
Problem scenario
You want the Apache web service to start automatically after a Linux server is rebooted. You want it to start automatically when you turn on a Linux server (after being off completely). On Linux CentOS you have this entry in /etc/crontab:
@reboot root apachectl start
You notice that on reboots (warm or soft) it works. But when you turn on your server after it has been off,
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Continue reading “How Do You Get the Apache Web Service to Start after a Cold Reboot?”
Problem scenario
You have to manually start Apache web server every time you do reboot the server. You want the Apache web service to start automatically.
Solution
1. Edit /etc/crontab. Add the lowest line of these two (the line above is for reference):
# * * * * * user-name command to be executed
@reboot root apachectl start
2.
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Problem scenario
Using a web browser you go to a PHP web page. There are no errors, but the page is blank. It is just all white, but you expect content to be rendered (e.g., text should be visible). The WSOD (white screen of death) is a common problem to troubleshoot in a web browser. What do you do to see output you want it to display?
Solution
1.
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Continue reading “How Do You Fix a PHP Web Page when the Page Is Completely Blank?”
Problem scenario
You have Postgres installed on the Linux guest of Oracle VirtualBox. You have storage capacity on the Windows host. You can interactively work with smbclient to share files between the Linux guest and the Windows host. You want to share files between the two servers without the interactive smb commands. You want the Postgres database to reside on the Windows host. This way your Linux guest hard disk does not have to be expanded but can run Postgres commands from your Linux guest.
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Problem scenario
You are using Oracle VirtualBox on a Windows host. You are using a Linux guest that is running Apache web server. The Apache httpd service is running on the guest Linux server. But when you are on the Windows host, you try to access the website, you get an error in the web browser. This is the error you receive:
“This address is restricted
This address uses a network port which is normally used for purposes other than Web browsing.
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Problem scenario: You have a Linux VM guest running on Oracle VirtualBox. You installed Apache web server on this server. How do you browse to its website from your Windows host machine?
Solution
#1 Determine the host IP address as configured for the guest. In Oracle VirtualBox go to Devices -> Network -> Network Settings. For Adapter1 go to “Advanced” and click the button for “Port Forwarding.” The host IP address may be 127.0.1.1.
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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.
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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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