important paths

~/ -> home directory of current user

/dev/ttyS0: The first serial port.
/dev/lp0: The first legacy LPT printer port.
/dev/hda: The master IDE device on IDE interface 0 (typically your hard drive).
/dev/hdb: The slave IDE device on IDE interface 0 (not always in use).
/dev/hdc: The master device on IDE interface 1 (typically your optical drive).
/dev/sda: The first SCSI or serial ATA device in your computer.
/dev/sdb: The second SCSI or serial ATA device in your computer.
/dev/sda1: The first partition on the first SCSI or serial ATA device in your computer.
/dev/tty1: The name of the first text-based console that is active on your computer (from tty1 up to tty12).
/dev/fd0: If available: the diskette drive in your PC.

/etc/apt/sources.list -> list of installation sources
/etc/default -> files with default values
/etc/group -> file with all groups
/etc/login.defs -> configuration file for users (password size, max min user nr)
/etc/nologin -> create this file and then nobody will be able to login (only root can!)
/etc/passwd -> users, home directories, primary group and standard shell uf users
/etc/profiles -> variables of each user
/etc/prifles.d -> folder to put in files to execute for the profile
/etc/security/limits.conf -> for limitations like file size, cpu time,
/etc/shadow -> file with encrypted passwords of the useres
/etc/shells -> alle vorhanden Shells aufegelistet
/etc/skel -> folder with default files for new users (copy files: tar cv . | tar xvC /home/zeina)
/etc/syslog.conf -> Logging on to Ubuntu Server is handled by the syslogd process.

/lib/modules -> enthält alle kernels

/proc/partitions -> partition tabe as the kernel is sees (refreshed after reboot) -> partprobe /dev/sdb

/usr/share/doc/ -> documentation about programs -> to read files: zcat changelog.gz | less

/var/lib/apt -> apt-get databse for package manager
/var/log -> all log files
/var/www -> document root for webserver