Articles tagged with #Linux




How to request Google, Cloudflare, and OpenDNS/Umbrella DNS servers cache clearing for your domain records

It is rare for these well-known DNS providers to cause problems to your domain records, but everything is possible. More often though, you may need to refresh some DNS record of your domain sooner than its TTL expires. Below you will find links how to do so for the aforementioned …



Nfdump netflow/sflow cookbook of examples

Start nfcapd netflow collector in a daemon mode listening on port 5001 with all extensions enabled and saving received netflow data into the named folder NFS-cisco-rtr. Accept netflow records only coming from the sender with the IP of 13.13.13.137 Read and print all records form a single …



AWS cli cookbook

Get a list of all the buckets under user account Recursively list contents of a given bucket yurisk.info Recursively list contents of a given bucket printing sizes in a friendly format List contents of a bucket, add summary for number of objects and their total size Get access-list associated …



Curl examples cookbook

Last updated: 19 December 2020 Get coronavirus/Covid-19 statistics for your country, real-time or historical Force curl not to show the progress bar Download a web page via GET request setting Chrome version 74 as the User-Agent. Download a web page via GET request setting Googlebot version 2.1 as …



MRV Optiswitch OS904 OS906 OS912 debug and diagnostic commands

MRV Communications (acquired in 2017 by ADVA Optical Networking) is an Israeli company known for their optical network equipment, most notably their Optiswitch Carrier Ethernet Switch series. The switches (OS904, OS906G, OS912) are not available for purchase from them anymore, but if you work for a telco company, you surely …



NMAP UDP DNS scan unexpected packets sending

I got the other day an automated mail alert from some ID/IPS equipment that ‘ a NULL DNS scan was detected and blocked from your IP’. NULL DNS scan? I wasn’t sending any such packets, not to mention I have no idea what they mean by that. After some …



NMAP run stages flow diagram

NMAP scanner has become over the years so friendly that it is not apparent what is going on when it runs. Below is a typicsl NMAP workflow:



Hex editor of binary files on Linux

Reading this thread on Stackoverflow http://stackoverflow.com/questions/5498197/need-a-good-hex-editor-for-linux I wondered how come with so many hex editors in Linux there is not really the best one. In Windows it is easier - the expensive WinHex or the affordable Hiew. Anyway, as to the Linux I always use Vim …



Public DNS servers open to any on the Internet

Following the good will by Google many other providers made their DNS servers available to us without any limitations as recursive resolvers. As they do not announce it widely enough you may not have heard abouth them, here is the list of these DNS servers: OpenDNS/Cisco Umbrella: 208.67 …



Linux ip route command reference by example

ip address - Manage IP address(es) on interfaces ip route - Manage routing table ip link - Link Management Interface Grouping. ip neighbor - Managing ARP table Tunnel interfaces GRE NOTE: All the commands below take effect immediately after you hit Enter, and do NOT survive reboot. ip address - Manage IP address(es …