imported>ThorstenStaerk |
imported>ThorstenStaerk |
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− | How Linux typically starts up on a PC
| + | #REDIRECT [[Mindmapping]] |
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− | = you switch on the computer =
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− | BIOS is shown and the devices are check
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− | = the master boot record is executed =
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− | = the boot loader is executed =
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− | The boot loader is typically grub, and there is an older and smaller called lilo.
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− | = the Linux kernel is executed =
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− | = the initrd is loaded/executed =
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− | = the init program is started =
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− | The Linux kernel starts the init program. Nothing else. If the init process quits, the Linux kernel panics. Init is responsible for all further services and programs that are started.
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− | | |
− | = the init script are executed =
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− | This can be SysV init scripts or upstart or systemd. These init scripts typically start services. Services are grouped into runlevels. Find out your current runlevel with the command
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− | runlevel
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− | Change your runlevel, in this case to 3, with the command
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− | init 3
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− | E.g. in SUSE the runlevels are defines as
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− | * 0: reboot
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− | * 1: rescue system, single user
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− | * 2: all services that run in (1) plus services needed for multi-user login
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− | * 3: all services that run in (2) plus network services
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− | * 4: undefined
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− | * 5: all services that run in (3) plus graphical display
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− | Some notable services are:
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− | * alsasound
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− | : Used for the alsa sound system
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− | * cups
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− | : Used for printing, it is the common Unix printing system
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− | * dbus
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− | : Used to call public functions in running programs. Should be abstracted to users.
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− | * esound
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− | : Used for enlightenment sound system
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− | * ntp
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− | : Network Time Protocol to keep your clock in sync with the real time via the network
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− | * autofs
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− | : To automount devices as soon as they are plugged in, e.g. USB disks and CD ROMs
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− | * udev
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− | : The udev services have a lot of names, e.g. boot.udev under SUSE. They create the device handles in the /dev folder, e.g. when you plug in a USB disk or attach a [[web cam]]
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− | * xdm
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− | : The x display manager shows a graphical login screen and starts a session when you log in. It keeps running during the session so when you end your session, you will be able to log in again.
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− | * cifs
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− | : mounts all cifs network drives
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− | * xfs
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− | : manages X fonts
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− | * cron
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− | : Cron executes jobs in given time intervals according to /etc/crontab
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− | * ypbind
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− | : provides information like login names, home directories and so on over the network
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− | * powerd
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− | : Makes sure to throttle down your computer's speed if there is nothing to do, it can save power and it is configured to do so.
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− | * network
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− | : The network service makes sure you have an IP address and your network card is active.
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− | * sshd
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− | : Service that allows to [[control a computer via the network]]
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− | = X Windowing system is started =
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− | = login manager is started =
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− | = user session incl. Desktop environment is started =
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− | = See also =
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− | * http://wiki.linuxquestions.org/wiki/Boot_process
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