IRQ (interrupt request) is a signal sent to the CPU to handle some external event (ie. keyboard input).
On x86, IRQs are numbered from 0 to 15; on x86-64, there are more than 16 IRQs.
Some interrupts are reserved for specific use, others have common uses. Continue reading “Managing hardware”
ps displays processes’ status. Syntax is as follows:
ps supports three different types of options:
- Unix98: may be grouped together and are preceded by a single dash
- BSD: may be grouped together and must not be preceded by a dash
- GNU long: never grouped together, preceded by two dashes
You can change default behavior by setting the PS-PERSONALITY environment variable to posix, old, Linux, bsd, sun, digital.
By default, ps displays only processes run from its own terminal. -A and -e options display all processes and -x displays processes owned by the user who gives the command. Continue reading “Managing processes”
One of the most important libraries is the C library (libc); another type of common library is associated with GUIs, often called widget sets. The GTK+ and Qt are the most popular.
Linux use the GNU C library (glibc); the main file is called /lib/libc.so.6 or /lib64/libc.so.6 (usually this is a symbolic link to another file).
Most programs use their libraries as shared libraries (aka dynamic libraries). Linux shared libraries have a .so or .so.ver extension (.so = shared object). Linux static libraries have a .a extension.
- Shared libraries can be incompatible but you can keep multiple versions
- Programs must be able to locate shared libraries so you most adjust config files and environment variables
- If an important library becomes inaccessible, you can have severe system issues
Continue reading “Managing libraries”
Problems with packages can be caused by:
- missing libraries or support programs
- incompatible libraries or support programs; in this case you can install multiple version of a library
- duplicate files or features
- mismatched names
Continue reading “Packages dependencies and conflicts”
alien can convert between RPMs, DEBs, stampede and tarballs. alien requires that you have appropriate package manager installed.
alien [options] [file]
alien –to-rpm [package].deb
If you use Debian-based systems and want to install a tarball but keep a record of the files it contains in your Debian database:
alien –install [binary.tar] .tar.gz