Articles tagged with #Linux




Network MTU maximum size path discovery (PMTU) testing with ping

MTU (MAximum Transmit Unit) plays central role in available throughput. And while with the Internet the maximum size isn’t going to surpass 1500 bytes, on MPLS/IPL/etc lines, owned by 1 provider, it is possible to get better MTU. THe easiest way to test for the maximum size …



GNU tar archive tool reference by example

Table of Contents Archive and gzip-compress the current folder with tar Archive and gzip-compress the current folder using maximal compression possible Set compression level as the GZIP environmental variable for gzip Set compression level by piping tar output to the gzip Use -I option for modern versions of tar Archive …



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

Table of Contents Introduction 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 …



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: Follow me on https://www.linkedin.com/in/yurislobodyanyuk/ not to miss what I publish on Linkedin, Github, blog, and more.



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 …