Aug 11

Ruby gem exception: invalid option

Below is my ‘quick fix’ (bandaid) solution to the following errors/exceptions. The errors Error: Execution of '/usr/bin/gem install --no-rdoc --no-ri cowsay' returned 1: ERROR: While executing gem ... (OptionParser::InvalidOption) invalid option: --no-rdoc Did you mean? no-force A reference article https://github.com/puphpet/puphpet/issues/2838 The ‘quick fix’ W.r.t. the reference article, I searched for the file ‘gem.rb’. Since ‘locate’ was not installed in the OS, I used the ‘find’ command to look for the file:

Ruby

1 min read

Ruby gem exception: invalid option

Below is my ‘quick fix’ (bandaid) solution to the following errors/exceptions.

The errors

Error: Execution of '/usr/bin/gem install --no-rdoc --no-ri cowsay' returned 1: ERROR:  While executing gem ... (OptionParser::InvalidOption)invalid option: --no-rdocDid you mean?  no-force

A reference article https://github.com/puphpet/puphpet/issues/2838

The ‘quick fix’

W.r.t. the reference article, I searched for the file ‘gem.rb’. Since ‘locate’ was not installed in the OS, I used the ‘find’ command to look for the file:

> find / -name 'gem.rb'
/usr/lib/ruby/vendor_ruby/puppet/provider/package/gem.rb

In the gem.rb file, I found the line throwing the exception and made the following modification:

#command << "--no-rdoc" << "--no-ri" << resource[:name]
command << "--no-document"  << resource[:name]

Aug 10

Puppet manifest not pulling

Continued from the previous post. As I am making full use of my 30-days free account in Azure, I have setup a pair of Puppet servers to test (with respect to the reference article at the bottom). A problem In the Puppet master, I have: /etc/puppet/manifests/site.pp with content file {'/tmp/example-ip'…

Puppet

1 min read

Aug 6

Azure Cloud Free Tier

I have just started using Azure cloud. As a frugal engineer, I will make full use of the 30 days free tier. As I added more VMs to my free account, it finally hit the limit. On the Virtual Machines page, I could not find a button to downsize the ones I already created (even if I power the VM down). So I started deleting them to free up the limit. But the following error persisted, even after I deleted every VM/refreshed the page:

Azure

1 min read

Azure Cloud Free Tier

I have just started using Azure cloud. As a frugal engineer, I will make full use of the 30 days free tier.

As I added more VMs to my free account, it finally hit the limit. On the Virtual Machines page, I could not find a button to downsize the ones I already created (even if I power the VM down). So I started deleting them to free up the limit.

But the following error persisted, even after I deleted every VM/refreshed the page:

“X vCPUs are needed for this configuration, but only 0 vCPUs (of 4) remain in your subscription.”

Eventually it turns out that there’s a need to click on the ‘Refresh quota’ link (a Blue hyperlink below the error), so it will get rid of the error.

Jul 21

Protectli Vault + pfSense

Lately I have tested Protectli Vault (with both OPNsense and pfSense). Below are some tips/takeaways. Protectli Vault The model I tested was FW6D — 6 Port Intel® i5. Protectli Vault - 6 Port Ports, power, customization: Meet the 6-Port Vaults, ideal for businesses and complex networks: Intel 3867U, i3-7020U…protectli.com Why Protectli Due to some physical constraints (of the place where my ISP placed the cable), I need a firewall without a lot of fan noise…

Firewall

4 min read

May 28

Graylog Dashboard for Nginx Logs

Graylog is a great tool to visualize and analyze what’s happening to your backend systems. Production log files are usually too noisy for human eyes, i.e. a tail -f on the log will show you the influx of new entries which are impossible for human eyes to catch. Moreover, logs…

Graylog

2 min read

Mar 23

TryHackMe: Write-Up Linux PrivEsc

Here’s a write-up for Task 10 and 12 in Room https://tryhackme.com/room/linprivesc The other tasks in the same room have intensive instructions which are relatively easy to follow. Task 10 was slightly more confusing. Task 12 is a challenge question with no instructions. Therefore I’ll only write for these tasks. Task…

Tryhackme

3 min read

Mar 16

Exporting Systemd service status with node exporter

Depending on which version of node exporter you are using, one of the following options will work. Node exporter version go1.14.4 /usr/local/bin/node_exporter \ --collector.systemd \ --collector.system.unit-whitelist=(graylog-server|mongod|elasticsearch).service Node exporter version go1.15.8 Since the option “collector.system.unit-whitelist” was deprecated, the syntax has changed to “collector.systemd.unit-include”.

Prometheus

1 min read

Exporting Systemd service status with node exporter

Depending on which version of node exporter you are using, one of the following options will work.

Node exporter version go1.14.4

/usr/local/bin/node_exporter \
--collector.systemd \
--collector.system.unit-whitelist=(graylog-server|mongod|elasticsearch).service

Node exporter version go1.15.8

Since the option “collector.system.unit-whitelist” was deprecated, the syntax has changed to “collector.systemd.unit-include”.

Note that there might be a bug in this version such that it won’t work if you put an equal (=) sign before the value:

/usr/local/bin/node_exporter \
--collector.systemd \
--collector.systemd.unit-include "(graylog-server|mongod|elasticsearch).service"

Oct 28, 2021

Logging

Logging plays an essential part of software applications. With well-written logs, it’s easy to retrieve event history, and speed up troubleshooting. Most devs tend to keep logs in the source code directory, which is fine if they are set to rotate off eventually. …

Logging

2 min read

Oct 27, 2021

Elasticsearch Administration

I have been using Graylog (community edition) for many years. The backend of Graylog is Elasticsearch DB, which stores the logs. Here are some Prometheus alerts to monitor Elasticsearch clusters, and some useful troubleshooting commands. Monitor Elasticsearch with Prometheus This shall not be confused with ‘collecting Prometheus data with Elasticsearch’…

Graylog

2 min read

Oct 27, 2021

PAM

PAM, or Linux Pluggable Authentication Modules Linux PAM - Wikipedia Linux Pluggable Authentication Modules (PAM) is a suite of libraries that allows a Linux system administrator to…en.wikipedia.org PAM stacks are not very easy to read. If you made a change but didn’t test it well, it might not work as expected. Or worse, you may end up exposing a vulnerability in your authentication mechanisms. Here are my notes about the 3 terms in the PAM stack:

Linux

1 min read

PAM

PAM, or Linux Pluggable Authentication Modules

Linux PAM - WikipediaLinux Pluggable Authentication Modules (PAM) is a suite of libraries that allows a Linux system administrator to…
en.wikipedia.org

PAM stacks are not very easy to read. If you made a change but didn’t test it well, it might not work as expected. Or worse, you may end up exposing a vulnerability in your authentication mechanisms.

Here are my notes about the 3 terms in the PAM stack:

required: keeps going (despite success or failure).

sufficient: it stops (disregards what’s below it) when succeeds. It will only be successful if no previous ‘required’ items have failed.

requisite: if this fails, stops and return failure