Linux: Chapter8: File Operations

"Sometimes we no need to explain, just take a look at pictures and you will conceive"

********************  Special Thanks ********************

R. Gordon

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SECTION 1 Command Line Mode

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Some examples of filesystem types that Linux supports are:

• ext3, ext4, btrfs, xfs (native Linux filesystems)
• vfat, ntfs, hfs (filesystems from other operating systems)

 /etc/fstab shows disk UUID

mount shows everything

df -Th  shows additional Type

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/proc/cpuinfo  looks like CPUz program

/proc/interrupts shows all Cores info

/proc/meminfo shows all about mem, buffer, cache

kevin@phoenix:/proc$ cat partitions 

major minor  #blocks  name

20 20 20 38 20 20 20 20 20 20 20 20 30 20 20 34 38 38 33 38 36 35 38 34 20 73 64 61 0A 20 20 20 38 20 20 20 20 20 20 20 20 31 20 20 20 20 20 31 30 32 34 30 30 20 73 64 61 31 0A 20 20 20 38 20 20 20 20 20 20 20 20 32 20 20 32 37 35 32 37 39 38 37 32 20 73 64 61 32 0A 20 20 20 38 20 20 20 20 20 20 20 20 33 20 20 32 31 33 30 30 32 32 34 30 20 73 64 61 33

kevin@phoenix:/proc$ 

kevin@phoenix:/proc$ cat version

Linux version 4.3.0-kali1-amd64 (debian-kernel@lists.debian.org) (gcc version 5.3.1 20160101 (Debian 5.3.1-5) ) #1 SMP Debian 4.3.3-5kali4 (2016-01-13)

kevin@phoenix:/proc$ 

kevin@phoenix:/proc$ uname -a

Linux phoenix 4.3.0-kali1-amd64 #1 SMP Debian 4.3.3-5kali4 (2016-01-13) x86_64 GNU/Linux

kevin@phoenix:/proc$ 

             -type c

              File is of type c:

              b      block (buffered) special

              c      character (unbuffered) special

              d      directory

              p      named pipe (FIFO)

              f      regular file

              l      symbolic  link;  this  is  never  true  if the -L option or the -follow option is in effect, unless the symbolic link is broken.  If  you  want to search for symbolic links when -L is in effect, use -xtype.

              s      socket

              D     door (Solaris)

This one made me wonder why it couldn't xargs tail -f?

Notice: please check arrow sign with 1st file and 2nd file

Directory name	Usage
/opt	Optional application software packages.
/sys	Virtual pseudo-filesystem giving information about the system and the hardware. Can be used to alter system parameters and for debugging purposes.
/srv	Site-specific data served up by the system. Seldom used.
/tmp	Temporary files; on some distributions erased across a reboot and/or may actually be a ramdisk in memory.
/usr	Multi-user applications, utilities and data.

Directory name	Usage
/usr/include	Header files used to compile applications.
/usr/lib	Libraries for programs in /usr/bin and /usr/sbin.
/usr/lib64	64-bit libraries for 64-bit programs in /usr/bin and /usr/sbin.
/usr/sbin	Non-essential system binaries, such as system daemons.
/usr/share	Shared data used by applications, generally architecture-independent.
/usr/src	Source code, usually for the Linux kernel.
/usr/X11R6	X Window configuration files; generally obsolete.
/usr/local	Data and programs specific to the local machine. Subdirectories include bin, sbin, lib, share, include, etc.
/usr/bin	This is the primary directory of executable commands on the system.

Disk-to-Disk Copying

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↞ Summary ↠

The key concepts covered in this chapter are:

• The filesystem tree starts at what is often called the root directory (or trunk, or /).
• The Filesystem Hierarchy Standard (FHS) provides Linux developers and system administrators a standard directory structure for the filesystem.
• Partitions help to segregate files according to usage, ownership and type.
• Filesystems can be mounted anywhere on the main filesystem tree at a mount point. Automatic filesystem mounting can be set up by editing /etc/fstab.
• NFS (The Network Filesystem) is a useful method for sharing files and data through the network systems.
• Filesystems like /proc are called pseudo filesystems because they exist only in memory.
• /root (slash-root) is the home directory for the root user.

• /var may be put in its own filesystem so that growth can be contained and not fatally affect the system.
• /boot contains the basic files needed to boot the system
• patch is a very useful tool in Linux. Many modifications to source code and configuration files are distributed with patch files as they contain the deltas or changes to go from an old version of a file to the new version of a file.
• File extensions in Linux do not necessarily mean that a file is of a certain type.
• cp is used to copy files on the local machine while rsync can also be used to copy files from one machine to another as well as synchronize contents.
• gzip, bzip2, xz and zip are used to compress files.
• tar allows you to create or extract files from an archive file, often called a tarball. You can optionally compress while creating the archive, and decompress while extracting its contents
• dd  can be used to make large exact copies even of entire disk partitions efficiently

Of course, I am an Artist~

Reference:

https://www.linuxfoundation.org
JAYz - { KevinChen 陳爱平}

Linux: Chapter7: Command Line Operations

"Intangible and invisible things may be meaningful. 

Tangible and visible things might mean nothing."

********************  Special Thanks ********************

ec2-107-xx-87-xxx.compute-1.amazonaws.com

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SECTION 1 Command Line Mode

   A terminal emulator program emulates (simulates) a stand alone terminal within a window on the desktop By default, on GNOME desktop environments, the gnome-terminal application is used to emulate a text-mode terminal in a window. Other available terminal programs include:

• xterm
• rxvt
• konsole
• terminator

xterm is used to emulate a graphical-mode terminal as I installed Oracle DBMS in Linux. 

Therefore, I think xterm, rxvt, kconsole and terminator might be the same but different Distros.

The X Window System

     Linux Distros provide both CLI and GUI. Production server should be CLI only since it's secured and lean system.

Turning off the Graphical Desktop

     Linux distributions can start and stop the graphical desktop in various ways. For Debian-based systems, the Desktop Manager runs as a service which can be simply stopped. For RPM-based systems, the Desktop Manager is run directly by init when set to run level 5; switching to a different runlevel stops the desktop.

      Use the sudo service gdm stop or sudo service lightdm stop commands, to stop the graphical user interface in Debian-based systems. On RPM-based systems typing sudo telinit 3 may have the same effect of killing the GUI. 

Remark: the killed system doesn't prompt at command line terminal. I mean, it's gone and need to power on again.

↞ sudo vs su ↠

• sudo allows users to run programs using the security privileges of another user, generally root (superuser).
• su (switch user) allows user to switch user to another one such as su - kevin
• "su - root"  and "su" and "su -" commands switch to root user but environments are different. You might find its differences in advance. 

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I have left out many details since I have known it.

Reference:

https://www.linuxfoundation.org
JAYz - { KevinChen 陳爱平}

Linux: Chapter6: Finding Linux Documentation

"It would be better to teach how to fishing rather than give them a fish", quoted by Anonymous.

********************  Special Thanks ********************

Her Royal Highness Princess Maha Chakri Sirindhorn,

Daughter to the Queen Regent who is citizens' idol on Technologies and Languages.

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SECTION 1 Documentation Sources

1. The man pages (short for manual pages)
2. GNU Info
3. The help command and --help option
4. Other Documentation Sources, e.g. https://www.gentoo.org/doc/en/, http://directory.fsf.org/wiki/Main_Page

                     man –f ~= whatis                   short description what it does, -f = fast (how to remember)
                     man –k ~= apropos               lists all things related to specific topic. -k = king (the king is a man who holds all things. technique to remember for me )

SECTION 2 GNU info

To install this command: sudo apt-get install info

          After go into info grep document, above pictures show you when pressing "N" or "Next". It means, go to next "Node"

         Notice: Next, Prev and Up at the top line of the console. I mean, we can press N, P and U as it mentioned.

SECTION 3 help command: -h or --help

SECTION 4 Other Documentation Sources

     In addition to the man pages, the GNU Info System, and the help command, there are other sources of Linux documentation, some examples of which are shown here.

Desktop Help Systems

        All Linux desktop systems have a graphical help application. This application is usually displayed as a question-mark icon or an image of a ship’s life-preserver. These programs usually contain custom help for the desktop itself and some of its applications, and will often also include graphically rendered info and man pages.

Warning: Sometimes sources might make a mistake. You have to work around and I found that Debian-based might use khelpcenter NOT gnome-help as shown below.

You can also start the graphical help system from a graphical terminal using the following commands:

• GNOME: gnome-help 
• KDE: khelpcenter

↞ Summary ↠

• The main sources of Linux documentation are the man pages, GNU Info, the help options and command, and a rich variety of online documentation sources. 
• The man utility searches, formats, and displays man pages.
• The man pages provide in-depth documentation about programs and other topics about the system including configuration files, system calls, library routines, and the kernel.
• The GNU Info System was created by the GNU project as its standard documentation. It is robust and is accessible via command line, web, and graphical tools using info.
• Short descriptions for commands are usually displayed with the -h or --help argument.
• You can type help at the command line to display a synopsis of built-in commands.
• There are many other help resources both on your system and on the Internet.

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Reference:

https://www.linuxfoundation.org
JAYz - { KevinChen 陳爱平}