How to build and install RGF (Regularized Greedy Forest) on Mac OS

Regularized Greedy Forest was introduced in this article. And now it is one of the approaches for efficient boosting training. However, building and installing it on Mac not yet (for November 2018) is as simple as pip3 install xgboost. So, this short note is about how to build and run RGF on Mac, if you have any troubles with it.

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How to send html-formatted email

Short answer: sending .html-formatted email is rather easy, even from a local laptop. But there can be difficulties, which are not avoided easily. To begin with, the short and (hopefully) working answer:

Mac OS | CentOS | Debian

cat letter.html | mail -s "$(echo -e "Testing email\nContent-Type: text/html")"

Make sure you check the SPAM folder, as it has nearly 0 chance of getting through to your mailbox from scratch. If it doesn’t work out, you’ll have to go deeper.

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Nagios doesn’t start / internal service error / PID unfound

Nagios web-interface can fail to connect to process or to display any content at all. There can be different source of the problem, but the key to solving it:

  1. Checking permissions on the cgi-bin, fcgi-bin folders and scripts inside /nagios path.
  2. Checking Suexec log if you use it (`/var/log/apache2/suexec.log` for example).
  3. Checking access mode on statusjson.cgi and status.cgi

In case it doesn’t help, and nagios simply refuses to start, showing only:

Running configuration check...
Starting nagios:.

You have to manually run configuration check with the -v flag:

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

If the check is correct, but nags refuses to run, providing no info in {path}/var/nagios.log and not creating {path}/var/nagios.lock, then the problem might be in the device space.

How to set up a ssh connection from Host to Guest VirtualBox

  1. VM’s Settings -> System -> check “Enable I/O APIC.”
  2. Shut the guest down, and use VirtualBox Settings to enable a second virtual network adapter, named (by default) vboxnet0.
  3. Inside Guest edit /etc/network/interfaces file or analogue and append the following lines:
    auto eth1
    iface eth1 inet dhcp


    allow-hotplug eth1
    iface eth1 inet dhcp
  4. In Guest start the interface: ifup eth1
  5. Test ssh root@[ip address from ifconfig in Guest] from Host system.
  6. Make sure you have root login enabled in Guest /etc/sshd_config settings.


Connecting to kernel jupyter/ipython error

There is a possibility, that you get

404 GET /nbextensions/widgets/notebook/js/extension.js

error in console and «Сonnecting to kernel»  or «No kernel» message in the web interface, this might be because of your browser bug. Try disabling adblock or using another browser.