This is a quick guide to mounting a qcow2 disk images on your host server. This is useful to reset passwords, edit files, or recover something without the virtual machine running.
Step 1 - Enable NBD on the Host
modprobe nbd max_part=8
Henri Menke hmenke
Manu343726
/ gist:ca0ceb224ea789415387
Created
September 19, 2015 18:15
Running ARM docker image with QEMU on x86_64 Arch Linux host
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| # Install quemu, docker, etc | |
| yaourt -S qemu qemu-user-static binfmt-support | |
| # The quemu-user-static AUR package is outdated and broken. The .deb package they pull is no longer in the ubuntu repository. | |
| # Edit the PKGBUILD and use qemu-user-static_2.4+dfsg-3_amd64.deb (With SHA1 sum "84d83a16c60c82b6c579f2f750b04a3ac26c249b") | |
| # Enable ARM emulation | |
| update-binfmts --enable qemu-arm |
morbusg
/ Unicode math in plain TeX
Created
March 6, 2014 12:36
Some Unicode math glyph definitions for use with plain XeTeX using a token list approach instead of family changes.
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| \Umathcharnumdef\aleph="2135 \Umathcharnumdef\hbar="210F | |
| \Umathcharnumdef\imath="1D6A4 \Umathcharnumdef\jmath="1D6A5 | |
| \Umathcharnumdef\ell="2113 \Umathcharnumdef\wp="2118 \Umathcharnumdef\Re="211C | |
| \Umathcharnumdef\Im="2111 \Umathcharnumdef\infty="221E | |
| \Umathcharnumdef\prime="2032 \Umathcharnumdef\emptyset="2205 | |
| \Umathcharnumdef\surd="221A \Umathcharnumdef\top="22A4 | |
| \Umathcharnumdef\bot="22A5 \Umathcharnumdef\|="2016 | |
| \Umathcharnumdef\angle="2220 \Umathcharnumdef\triangle="2206 | |
| \Umathcharnumdef\backslash="005C \Umathcharnumdef\forall="2200 | |
| \Umathcharnumdef\exists="2203 \Umathcharnumdef\neg="00AC |
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| #!/bin/sh | |
| # Take a PDF, OCR it, and add OCR Text as background layer to original PDF to make it searchable. | |
| # Hacked together using tips from these websites: | |
| # http://www.jlaundry.com/2012/ocr-a-scanned-pdf-with-tesseract/ | |
| # http://askubuntu.com/questions/27097/how-to-print-a-regular-file-to-pdf-from-command-line | |
| # Dependencies: pdftk, tesseract, imagemagick, enscript, ps2pdf | |
| # Would be nice to use hocr2pdf instead so that the text lines up with the PDF image. | |
| # http://www.exactcode.com/site/open_source/exactimage/hocr2pdf/ |
RhysU
/ gist:5281465
Last active
March 18, 2021 11:35
Using Boost Spirit 2.1+ to evaluate constant arithmetic expressions.
See http://agentzlerich.blogspot.com/2011/06/using-boost-spirit-21-to-evaluate.html
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| //-------------------------------------------------------------------------- | |
| // | |
| // Copyright (C) 2011, 2012, 2013 Rhys Ulerich | |
| // Copyright (C) 2012, 2013 The PECOS Development Team | |
| // Please see http://pecos.ices.utexas.edu for more information on PECOS. | |
| // | |
| // This Source Code Form is subject to the terms of the Mozilla Public | |
| // License, v. 2.0. If a copy of the MPL was not distributed with this | |
| // file, You can obtain one at http://mozilla.org/MPL/2.0/. | |
| // |
jboner
/ latency.txt
Last active
December 8, 2025 14:53
Latency Numbers Every Programmer Should Know
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| Latency Comparison Numbers (~2012) | |
| ---------------------------------- | |
| L1 cache reference 0.5 ns | |
| Branch mispredict 5 ns | |
| L2 cache reference 7 ns 14x L1 cache | |
| Mutex lock/unlock 25 ns | |
| Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
| Compress 1K bytes with Zippy 3,000 ns 3 us | |
| Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
| Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |
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| -- xml parser | |
| local require,lpeg,io,select,string,type,tonumber,tostring=require,lpeg,io,select,string,type,tonumber,tostring | |
| local w = w | |
| local printtable=printtable | |
| module(...) | |
| bit = require('bit') | |
| local C,P,R,S,V = lpeg.C,lpeg.P,lpeg.R,lpeg.S,lpeg.V |
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| -- | |
| -- viznodelist.lua | |
| -- speedata publisher | |
| -- | |
| -- Written 2010-2020 by Patrick Gundlach. | |
| -- This file is released in the spirit of the well known MIT license | |
| -- (see https://opensource.org/licenses/MIT for more information) | |
| -- | |
| -- visualizes nodelists using graphviz |
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