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Backblaze B2 via rclone cheatsheet

• Create B2 remote
• Tasks
  • List buckets
  • Synchronize local files to bucket
  • Synchronize local files to bucket - checksum
  • Verify local files against bucket
• Reference

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VirtualBox create host-only interface and attach

A host-only network interface is created virtually in software which appears to the host system.

This interface can be attached to one or more VMs, allowing connectivity between those VMs and communication between the host system and VMs.

• Create & attach interface
• Configure Ubuntu guests
  • Ubuntu 18.04+
  • Ubuntu pre 18.04

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Git correct a commit via --fixup

Initial commit state:

$ git log --oneline
733e2ff Second widget done
fb2f677 First widget done
ac5db87 First commit

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Modify DNS for Optus supplied Huawei B315 4G modem

The Huawei B315 modem supplied by Optus for the (now defunt) Vividwireless service is a workable but sadly rather crippled device, even down to the inability to modify assigned DNS servers from it's DHCP server away from Optus DNS to something sane (Google DNS/Cloudflare/etc.).

This script should allow for the easy update of assigned DNS servers and has been tested with Google Chrome.

Usage

• Log into router web UI (e.g. http://192.168.0.1).
• From the same browser session, open the "web developer tools" pane.

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GitHub pull request toggle "force-pushed" events bookmarklet

Since November 2018, GitHub have started to display forced push events to pull request page timelines. This bookmarklet will toggle display of these events if they are getting in the way of meaningful commits.

Add the code below as the URL of a new bookmark:

javascript:((d)=>{if(d.getElementById('nuke-fp')==null){let e=d.createElement('style');e.id='nuke-fp';e.innerHTML='.nuke-fp{display:none}';d.getElementsByTagName('head')[0].appendChild(e)}for(let e of Array.from(d.querySelectorAll('.discussion-timeline .discussion-item-head_ref_force_pushed'))){e.classList.toggle('nuke-fp')}})(document)

Tested with Chrome 70.0.3538.102.

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'use strict';

async function* delayList() {

	function delay(timeout) {

		return new Promise((resolve,reject) => {

			setTimeout(() => resolve(`dealyed for: ${timeout}ms`),timeout);
		});

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CIDR fit

Python function to determine if a given IPv4 CIDR fits into another.

How cidr_fit(cidr_a,cidr_b) works:

• For both CIDR's given:
  • Splits each CIDR into address and prefix size parts.
  • Converts the address part to a 32 bit binary string.
    • Example: 192.168.0.1 becomes 11000000101010000000000000000001.

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Gmail retention/purge by label Google script

A Google Apps Script which adds pseudo message retention-like policies against specific labels for a Gmail account.

• How it works
• Install
• Reference

How it works

• Apps Script function is called automatically on a regular schedule.
• Script iterates over a set of predefined message labels.

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Add user ssh-agent as daemon to Ubuntu 18.04LTS server

Create a new systemd user unit, which starts ssh-agent upon login to server. Will remain resident until the final session for the user has logged out.

Steps

• Create /etc/systemd/user/ssh-agent.service.

• Run the following commands (under your user account, not root) to install the systemd unit and start:

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Bash shift quirks

When using the shift built-in, have noted this interesting behavior which I have been unable to find documentation for.

Update: the answer was right in front of me, if shift is called with a value greater than arguments available in $1 - $x then it will return with a non zero status - hence the script will halt (since I'm using set -e)!

Using the script test.sh, executed using arguments:

./test.sh apple orange banana
apple