Posted by Georg Sauthoff in linux
This article illustrates how the virtual memory (VM) subsystem of the Linux kernel is able to cache files that are located on an NFS server.
In this small experiment we just need two Linux machines on a local network, where one …
Posted by Georg Sauthoff in linux
Debian recently released a warning advisory regarding a hardware bug in the hyperthreading implementation on certain Skylake/Kaby Lake Intel CPUs. It can be mitigated by a microcode firmware update - at least on some models. This article is about checking a non-Debian system for this issue and verifying if the …
Posted by Georg Sauthoff in android
A stock Android device is locked down, by default. Rooting
is the process of getting access to the root user (think: installing
su). This article lists several advantages of a rooted device.
Posted by Georg Sauthoff in linux
Grml is a Linux Live CD distribution geared towards system administration tasks and other console work. Unfortunately, its development has slowed down in the past years, i.e. the latest stable release is from 2014. In 2017, when dealing with modern hardware, modern features like Btrfs, SELinux etc. this is …
Posted by Georg Sauthoff in misc
The firmware updates for the Samsung 840 EVO SSDs come as ISO images which isn't very helpful if your system doesn't have a CDROM drive. It turns out that the ISO images just contain DOS binaries, though. This article describes how to use a FreeDOS USB stick for flashing, instead …
Posted by Georg Sauthoff in linux
Traditionally, UNIX filesystems also maintain the access time (atime) of a file. This is very much an anti-feature because it yields a write operation for each read operation. Which is obviously bad for performance. Since Btrfs is a copy-on-write (COW) filesystem maintaining atimes is even more painful. Thus, a sensible …
Posted by Georg Sauthoff in misc
Dell distributes BIOS updates for the Latitude E7270 as PE32 Windows GUI executables. It turns out that the BIOS itself is able to extract the firmware images from such executables and to apply them.
https://www.dell.com/support/home …Posted by Georg Sauthoff in network
When sending a POST request with curl it sometimes automatically
adds an Expect: 100-continue header. The following summarizes under
which conditions curl/libcurl adds this header.
The Expect: 100-continue header is specified in HTTP 1.1 and
allows the server to acknowledge or reject a POST/PUT request
immediately …
Posted by Georg Sauthoff in network
The Link Layer Discovery Protocol (LLDP) probably isn't the most popular protocol but it can be useful for troubleshooting purposes and for mapping the neighbourhood of a host.
Its purpose is basically to send/receive key/value pairs that are of general interest. For example the switch port number the …
Posted by Georg Sauthoff in C++
This article discusses hardware performance counter measurements obtained for a character search benchmark running on Intel x86 and SPARC hardware. Those results help to explain the big runtime differences between a SPARC T5 system and Intel x86 ones (SPARC being much slower), as well as differences between the different implementations …