Archives: Linux

gdb and signal handling ( especially sigwaitinfo ) No ratings yet.

How gdb generally works In a debugging session, when the debugger wants to set a breakpoint, it replaces an instruction by int3 When the trap instruction (0xCC on x86) is executed, the processor notifies the OS. On UNIX, the OS checks to see whether the process is being ptraced by somebody. If no, the SIGTRAP signal is delivered to • Read More »


srtp and h.235.6 secure rtp No ratings yet.

SRTP RFCs and h.235 is Not an easy read. Here is my very high level beriefing: AES Encryption (1) AES is the foundation for both srtp and h.235.6 secured rtp AES is symmetric encryption,  it takes those two as input key + IV:  128/192/256-bits length key , ( + optional Initialized vector or counter) src input:    • Read More »


openstack 5/5 (1)

I spent several days to install openstack on debian 8 at one testing box with two NICs. Finally got a basic working system! It has with a controller node running neutron, glance and horizon, a compute node using KVM. To get much speed, one KVM VM is created as a controller node on that box, at the same • Read More »


docker No ratings yet.

Finally I got some chances to package one application using docker, here are some useful commands docker images: docker build –rm -t my_tag docker_dir ( with Dockerfile) docker images , docker rmi ( remove docker image) docker containers docker run -d –publish 9080:80 –publish 1022:22 –name container_name –restart always –voloume host_dir:container_dir -e HOST_UID=$(id -u) $tag • Read More »




socat introduction No ratings yet.

While searching a command line to write something into a UNIX Domain Socket, I found this great tool called socat which is similar to netcat/samplicator but has more features. The man page said: Socat is a command line based utility that establishes two bidirectional byte streams and transfers data between them. Because the streams can • Read More »



systemctl cheatsheat No ratings yet.

  Systemd template and instance (@) from: https://wiki.archlinux.org/index.php/systemd Note: Some unit names contain an @ sign (e.g. name@string.service): this means that they are instances of a template unit, whose actual file name does not contain the string part (e.g. name@.service). string is called the instance identifier, and is similar to an argument that is passed • Read More »