A Technical I.T./DevOps Blog
Problem Scenario
You are writing a PowerShell script. You want to extract one value from the results of a command. You get a set of values all on one line. It is difficult to parse just what you need. The output values for each attribute are separated by spaces. Sometimes the output values are blank. You want to reliably extract one property value from the command. You know that piping the output to an “sls” command will retrieve an entire row.
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Problem scenario: You know how to assign variables in a Bash script. But how do you assign the output of a complex command such as this?
cat foo.txt | grep continual | grep integration | uniq
To push the output of some compound statement into a text file is simple. Sometimes you want to redirect everything to a variable. How do you do this?
Solution:
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Two problem scenarios and solutions.
Problem scenario: You installed Cloudera 5 (Hadoop) on CentOS 7.2 for the first time. You tried to start the Cloudera database service. But you get an error that it failed.
You run this: systemctl status cloudera-scm-server-db.service
The results include this fragment: ” … Failed to start LSB: Cloudera SCM Server’s Embedded DB.”
How do you start the Cloudera DB service?
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Continue reading “How Do You Configure Linux To Be Ready for Cloudera 5 (Hadoop)?”
Problem scenario: You try to mount a file share with this command:
mount continualintegration.com:/export/path/to /mnt
You get this error:
” mount: wrong fs type, bad option, bad superblock on continualintegration.com:/export/path/to,
missing codepage or helper program, or other error
(for several filesystems (e.g. nfs, cifs) you might
need a /sbin/mount.<type> helper program)
In some cases useful info is found in syslog – try dmesg | tail”
Solution:
#1
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Question: How do you see the exact time when previous commands were entered on a Linux server when you use the “history” command?
Background: Linux by default logs the time and day when commands were issued. (There is a limit to the number of previous commands that stay logged.) The timestamps by default are not visible.
Solution: For the session,
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Continue reading “How Do You See The Time Previous Commands Were Entered On A Linux Server?”
Problem Scenario: You are using Puppet Master on Linux and Puppet Agent on Windows servers. The manifest attempts to copy to or from a Windows network file share, but you are getting an error about the network path not existing. The network file share has permissions that are open to Everyone. What do you do?
Solution: Puppet Agent will run PowerShell commands under the security context of the user who runs the “puppet agent -t -d” command.
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Continue reading “Puppet Needs To Use a Windows Network File Share: How Is This Done Consistently?”
Problem scenario: One Puppet manifest relies on another manifest to work. Trying to apply them at the same time is not working. The “require” and “before” keywords only seem to work for packages, exec, and file resources. What do you do to order the manifests to satisfy dependency requirements of other manifests?
Solution: The relationship dependency can be solved by the order in which they are applied.
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Background: Text-based browsers are fast. Operations can be scriptable and repeatable.
Question: How Do You Use a Text-Based Web Browser on RedHat Linux?
Prerequisites: You have access to the Internet and root access.
Solution: As root, enter these two commands (where “#” is the command prompt).
# yum-config-manager –enable rhui-REGION-rhel-server-extras rhui-REGION-rhel-server-optional
# yum -y install lynx
To test it out,
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Continue reading “How Do You Use a Text-Based Web Browser on RedHat Linux?”
Update on 3/30/17: The Puppet IIS module has been updated, and the problem below has been eliminated.
Problem scenario: You want Puppet to install IIS. You install the IIS module and find the README.md file has this Puppet DSL (as of 12/13/16):
class mywebsite {
iis::manage_app_pool {‘my_application_pool’:
enable_32_bit =true,
managed_runtime_version =’v4.0′,
}
iis::manage_site {‘www.mysite.com’:
site_path =’C:\inetpub\wwwroot\mysite’,
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Question
How Do I Assign User Input from a Bash Script to a Variable?
Answer
The script below will read in two variables. One will be referred to as $remoteIP and the other will be referred to as $remotePort later in the script. The “$” symbol will evaluate the variable so its value will participate in the expression (e.g., for echoing to the screen or manipulating for conditional logic) later in the script.
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Continue reading “How Do I Assign User Input from a Bash Script to a Variable?”