knowledge/technology/linux/Linux.md

obj	wiki	website
os	https://en.wikipedia.org/wiki/Linux	https://www.kernel.org

Linux

Linux is a kernel and computing platform.
It support virtually every filesystem. Linux has many distributions, such as Arch Linux or Alpine Linux, Proxmox, etc.
The default init system is Systemd. See mkinitcpio for other boot time configuration.
Linux has GUIs but is generally used with the Shell. The kernel development can be tracked here

Filesystem Structure

A typical Linux system has, among others, the following directories:

Path	Description
/	This is the root directory. This is where the whole tree starts.
/bin	This directory contains executable programs which are needed in single user mode and to bring the system up or repair it.
/boot	Contains static files for the boot loader. This directory holds only the files which are needed during the boot process. The operating system kernel (initrd for example) must be located in either / or /boot.
/dev	Special or device files, which refer to physical devices.
/etc	Contains configuration files which are local to the machine.
/home	On machines with home directories for users, these are usually beneath this directory, directly or not.
/lib	This directory should hold those shared libraries that are necessary to boot the system and to run the commands in the root filesystem.
/lib/modules	Loadable kernel modules (optional)
/lost+found	This comes from Ext4. This directory contains items lost in the filesystem.
/media	This directory contains mount points for removable media such as CD and DVD disks or USB sticks.
/mnt	This directory is a mount point for a temporarily mounted filesystem.
/proc	This is a mount point for the proc filesystem, which provides information about running processes and the kernel.
/root	This directory is usually the home directory for the root user (optional).
/run	This directory contains information which describes the system since it was booted. Once this purpose was served by /var/run and programs may continue to use it.
/sbin	Like /bin, this directory holds commands needed to boot the system, but which are usually not executed by normal users.
/sys	This is a mount point for the sysfs filesystem, which provides information about the kernel like /proc, but better structured, following the formalism of kobject infrastructure.
/tmp	This directory contains temporary files which may be deleted with no notice, such as by a regular job or at system boot up.
/usr	This directory is usually mounted from a separate partition. It should hold only shareable, read-only data, so that it can be mounted by various machines running Linux.
/usr/bin	This is the primary directory for executable programs. Most programs executed by normal users which are not needed for booting or for repairing the system and which are not installed locally should be placed in this directory.
/usr/etc	Site-wide configuration files to be shared between several machines may be stored in this directory. However, commands should always reference those files using the /etc directory. Links from files in /etc should point to the appropriate files in /usr/etc.
/usr/include	Include files for the C compiler.
/usr/lib	Object libraries, including dynamic libraries, plus some executables which usually are not invoked directly. More complicated programs may have whole subdirectories there.
/usr/share	This directory contains subdirectories with specific application data, that can be shared among different architectures of the same OS.
/usr/share/doc	Documentation about installed programs (optional).
/usr/share/man	Manual pages go here in subdirectories according to the man page sections.
/var	This directory contains files which may change in size, such as spool and log files.
/var/cache	Data cached for programs.
/var/log	Miscellaneous log files.