Before we move on to learning commands used in Linux. Let us walk through the important Linux Directories, Configuration files and block devices in Linux.
It is important that we understand the file system in linux and also have a basic knowledge about where the programs reside in the machine, where to look for what and how to make it easy for ourselves when working on a Linux machine.
$HOME/.bash_profile - bash system wide and per user init files
$HOME/.bashrc - bash system wide and per user init files
/ - The root of the filesystem, all other files and directories use this as a starting point.
/bin/ - Binaries Directory--contains common executables for system operation, and cannot contain subdirectories in order to comply with HFS conventions. This is a STANDARD directory.
/boot/ - Directory containing pertinent boot information and executables, such as the kernel, and initrd, grub.conf. Must be within 1024 cylinders from the start of the physical disk.
/dev/ - Devices Directory. This is a STANDARD Directory.
/dev/fd0 - Block device that refers to the first floppy drive.
/dev/lp0 - Block device that refers to the first parallel port (ie LPT1 in DOS/Windows).
/etc/ - Configuration Files Directory. This is a STANDARD Directory.
/etc/auto.master - auto mount master file.
/etc/bash.bashrc - Shell variables. Executes right after /etc/profile and /etc/profile.local on login. Executes upon opening every new shell./etc/bash.bashrc contains: - $PS1 - User command prompt - ALIAS - Aliases - Link to /etc/bash.bashrc.local NOTE: Any changes should NOT be done in this file, but rather in the /etc/bash.bashrc.local file.
/etc/bash.bashrc.local - Overrides /etc/bash.bashrc Changes should ONLY be made in THIS file instead of in the /etc/bash.bashrc file.
/etc/bashrc - bash system wide and per user init files.
/etc/cron.* - There are 4 directories that automatically execute all scripts within the directory at intervals of hour, day, week or month
/etc/default - Default for certain commands.
/etc/exports - NFS server export list.
/etc/fstab - List of block devices and their associated mount points and mount options.
/etc/ftpusers - User names excluded from the default operational mode of the ftp server. Ie. If all users are denied then these are all of the users who are allowed, and if all users are allowed then these are those who are disallowed.
/etc/group - Group listing, passwords, and member lists.
/etc/host.allow - TCP wrapper host control files, allows these systems to connect.
/etc/host.conf - host name information look up order
/etc/host.deny - TCP wrapper host control file denies listed systems from connecting.
/etc/HOSTNAME - Full hostname including domain
/etc/hosts - A list of all known host names and IP addresses
/etc/hosts.equiv - Host list of computers that are trusted to use rsh (remote shell).
/etc/hosts.lpd - Host list of computers that are trusted to send lpr commands to this system.
/etc/httpd/conf/ - Directory for Apache Web Server configuration
/etc/init.d/ - Directory containing runlevel scripts for system startup
/etc/inittab - Control file that determines how the system boots
/etc/inittab - Control file that determines how the system boots.
/etc/lilo.conf - LInux Loader configuration that specifies boot options, kernels, and other boot parameters. NOTE: Lilo must be re-run after changes are made to lilo.conf
/etc/lpd.conf - Line Printer Daemon configuration file
/etc/lpd.perms - Line Printer Daemon permissions configuration file
/etc/motd - Message of the Day broadcast to all users on login
/etc/networks - File that contains network ranges and their associated names
/etc/nsswitch.conf - Configuration file that defines the order in which lookup of hostnames/dns names occurs
/etc/passwd - File that has information that defines user accounts on the server, their shell, UID, default group, home directory, and either a hash for their password or a marker indicating that it is in the shadow password file.
/etc/printcap.local - Printer database, changes should be made here as /etc/printcap is regenerated each time the daemon loads. This file is not used nor referenced with a CUPS solution.
/etc/profile - Sets up shell variables that are global for everyone. Loaded right after login. Executes once only at login.
/etc/profile.local - Changes to your global variables should be made here.
/etc/protocols - This file contains protocol IDs and their names. Useful for determining network traffic problems.
/etc/rc.d/init.d/lpd - [option] should be replaced with start - Starts the print daemon, status - Displays the status of the print daemon, stop - Stops the print daemon
/etc/rc.d/rc.inet1 - IP address, Network mask, Default gateway are in these files. May edit manually to modify network parameters.
/etc/rc.d/rc.local - Bash script that is executed at the end of login process - like autoexec.bat in DOS
/etc/resolv.conf - Defines IP addresses of DNS servers
/etc/rpc - RPC service name to their program numbers mapping.
/etc/services - TCP/IP services and ports mapping.
/etc/shadow - Read-only to Root access processes, used to avoid theft of user passwords.
/etc/shells - The /etc/shells file serves as the list of valid shells that may be loaded.
/etc/skel/ - Template folder that contains files - for new users.
/etc/smb.conf - Configuration for the SAMBA server to allow file and print sharing with Windows clients
/etc/sysconfig/ - A directory containing system configuration files.
/etc/sysconfig/network - The networking configuration file, specifies network interfaces, IP addresses, and other protocols.
/etc/X11/XF86Config - Configuration file for XFree86's X Server
/home/ - The mountpoint or directory where user's personal data is stored. This is an OPTIONAL directory.
/lib/ - Library Files Directory. This is a STANDARD Directory.
/mnt/ - Mount Point Directory. This is a STANDARD Directory.
/opt/ - Optional Directory. This is a STANDARD Directory.
/proc/ - Kernel Process Information Directory. This is an OPTIONAL Directory.
/proc/interrupts - Contains which interrupts are in use and which are available.
/proc/ioports - Contains which I/O addresses are in use and which are available.
/proc/pci - Lists which PCI devices are already installed and their I/O addresses and interrupts.
/root/ - Root User's Home Directory. This is an OPTIONAL Directory.
/sbin/ - System Binaries Directory. This is a STANDARD Directory.
/srv/ - This directory is used for services' runtimes and working files. This is an OPTIONAL Directory.
/tmp/ - Temporary Director. This is a STANDARD Directory.
/usr/ - This directory is used as a system resource. Many times, libraries, applications, and source code are installed in this folder. Kernel compiling usually takes place in the /usr/src/linux/ subdirectory. This is a STANDARD directory.
/var/ - Logfiles are generally stored in the /var directory or log subdirectory. Variable data from applications and some binaries are installed here. This is a STANDARD directory.
~/.Xdefaults - Defines some parameters for X-Windows (~ refers to user's Home Directory)
~/.xinitrc - Defines windows manager loaded by X-Windows (~ refers to user's Home Directory) X Window Keystrokes : - ctrl+alt+backspace - Stop X server (some systems use ctrl+alt+esc) - ctrl+alt+F1 - Switch to text mode console 1, ctrl+alt+F7 - Switch back to graphic mode
