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@antonlindstrom
antonlindstrom / dnscheck
Created July 22, 2011 10:13
keepalived for DNS
#!/bin/bash
#$Id: keepalivepin,v 1.2 2006/02/27 07:30:41 hmy Exp hmy $
#use dig check the powerdns's status.
#in the dns database,have a IN TXT RR keepalivepin.vmmatrix.net,content is "AaBbCcDdEeFf"
# Source: http://puppet-manifest-share.googlecode.com/svn/trunk/vmx-puppet/modules/lvs/files/keepalived.dns-pin
#
RR=keepalivepin.vmmatrix.net
[ $# -le 1 ]&&{ echo "usage: ${0} -h <ip>"; exit 126;}
while getopts "h:" OPT;do
case $OPT in
@jboner
jboner / latency.txt
Last active January 7, 2026 15:51
Latency Numbers Every Programmer Should Know
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
@edmonds
edmonds / dnstap.txt
Last active February 29, 2024 16:55
example formatted output from dnstap command-line tool
21:08:07.858612 CQ 127.0.0.1 UDP 40b "dnstap.info." IN A
21:08:07.858604 RQ 192.5.5.241 UDP 28b "." IN NS
21:08:07.872825 RR 192.5.5.241 UDP 857b "." IN NS
21:08:07.872825 RQ 192.5.5.241 UDP 40b "dnstap.info." IN A
21:08:07.901990 RR 192.5.5.241 UDP 686b "dnstap.info." IN A
21:08:07.901990 RQ 199.254.49.1 UDP 40b "dnstap.info." IN A
21:08:07.964484 RR 199.254.49.1 UDP 596b "dnstap.info." IN A
21:08:07.964484 RQ 192.5.5.241 UDP 48b "ns7.dnsmadeeasy.com." IN AAAA
21:08:07.964484 RQ 192.5.5.241 UDP 48b "ns7.dnsmadeeasy.com." IN A
21:08:07.979984 RR 192.5.5.241 UDP 743b "ns7.dnsmadeeasy.com." IN AAAA
@arr2036
arr2036 / delay.sh
Last active November 26, 2024 14:25
Simple script to introduce delay on outbound packets to one or more (run multiple times) ip addresses
#!/bin/bash
# root qdisc handle
r_handle=1
# netem qdisc handle
n_handle=2
interface=
delay=
dstip=
qdpresent=
@upa
upa / LICENSE
Last active August 23, 2022 16:42
Ansible Module for Linux Bridge and VLAN
MIT License
Copyright (c) 2021 Ryo Nakamura
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
@shamil
shamil / mount_qcow2.md
Last active December 23, 2025 16:33
How to mount a qcow2 disk image

How to mount a qcow2 disk image

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
@wvengen
wvengen / extend.sh
Last active September 27, 2025 02:40
Extend non-HiDPI external display above HiDPI internal display
#!/bin/sh
# extend non-HiDPI external display on DP* above HiDPI internal display eDP*
# see also https://wiki.archlinux.org/index.php/HiDPI
# you may run into https://bugs.freedesktop.org/show_bug.cgi?id=39949
# https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/883319
EXT=`xrandr --current | sed 's/^\(.*\) connected.*$/\1/p;d' | grep -v ^eDP | head -n 1`
INT=`xrandr --current | sed 's/^\(.*\) connected.*$/\1/p;d' | grep -v ^DP | head -n 1`
ext_w=`xrandr | sed 's/^'"${EXT}"' [^0-9]* \([0-9]\+\)x.*$/\1/p;d'`
@ValdikSS
ValdikSS / donotasktoask_ru.md
Last active May 6, 2025 14:42
Спрашивайте сразу

Вам отправили это сообщение по следующим возможным причинам:

  • Вы поприветствовались и ждете ответа
  • Вы спросили о том, можно ли задать вопрос, и ждете ответа
  • Вы скинули запрос авторизации и ждете ответа

Пожалуйста, не делайте так. Задавайте вопрос сразу, без прелюдий, без запросов авторизации (в том числе и в Jabber), и ждите ответа. Не повторяйте свой вопрос и не спрашивайте, на месте ли я.

Здесь комментарии не пишите, уведомление о них не приходит ни мне, ни вам.

Если вам интересно получить развернутый ответ и аргументы, почему не стоить здороваться и ожидать ответа при общении онлайн:

@nerdalert
nerdalert / Netfilter-IPTables-Diagrams.md
Last active December 17, 2025 19:06
Linux NetFilter, IP Tables and Conntrack Diagrams

Linux NetFilter, IP Tables and Conntrack Diagrams

IPTABLES TABLES and CHAINS

IPTables has the following 4 built-in tables.

1) Filter Table

Filter is default table for iptables. So, if you don’t define you own table, you’ll be using filter table. Iptables’s filter table has the following built-in chains.

@alexey-milovidov
alexey-milovidov / rounding_time.txt
Created June 20, 2016 21:00
Example of rounding time to 5-second interval in ClickHouse.
:) SELECT toDateTime(intDiv(toUInt32(EventTime), 5) * 5) AS k, count(), uniq(UserID) FROM hits_layer WHERE CounterID = 29761725 AND EventDate = today() AND EventTime >= now() - 600 GROUP BY k ORDER BY k
SELECT
toDateTime(intDiv(toUInt32(EventTime), 5) * 5) AS k,
count(),
uniq(UserID)
FROM hits_layer
WHERE (CounterID = 29761725) AND (EventDate = today()) AND (EventTime >= (now() - 600))
GROUP BY k
ORDER BY k ASC