[SOLVED] network copy, how do I do it?

EldonCool · 04-06-2011, 12:31 AM

I cannot figure out how to copy files over my
network between my two computers.

Does anyone know a good source that tells how to
do this?

I have done it before, but don't remember all the
things I had to go through to do it.

None of the instructional things that I have found
has given me actual instructions that I understand.

Actually I have not even found instructions for
using scp that I can understand. I have all ready
done this in the past, yet with 30 years experience
with computers, a bachelors degree in computer
science, 20 years experience with linux I still
cannot understand anything that I have found that
tells how to do this.

I have two problems.
(1) the actual syntax of scp. None of the instructions
I have found tell what anything is in their examples.

They might say:

scp blah blah yadda yadda zonk zonk.

They don't bother to tell me what blah blah is or
what yadda yadda is, or what zonk zonk is.

(2) Also none of them tells what has to be set up in
configuration files for things to work. For example
one of my computers is named KING, and one is named
QUEEN. There is probably something on computer KING
that tells what QUEEN is. I don't know what this
configuration file is, so of course I can't put in
the entries that would do the job.

So where are some instructions that I might find for
doing this copy of files over my network of two
computers?

willysr · 04-06-2011, 01:23 AM

Code:

scp sourcedir/sourcefile username@host:/path/to/target

titopoquito · 04-06-2011, 03:04 AM

Quote:

Originally Posted by EldonCool

I cannot figure out how to copy files over my
network between my two computers.

As Willysr, I suggest scp

Quote:

I have two problems.
(1) the actual syntax of scp. None of the instructions
I have found tell what anything is in their examples.

I beg your pardon if this sounds ironic, but it isn't intended as that. Have you tried "man scp"? The options are explained quite good I think, only those specific to ssh are not all explained in that manual side but there are links given to other man pages that could explain that if you need it.

Quote:

(2) Also none of them tells what has to be set up in
configuration files for things to work. For example
one of my computers is named KING, and one is named
QUEEN. There is probably something on computer KING
that tells what QUEEN is. I don't know what this
configuration file is, so of course I can't put in
the entries that would do the job.

KING and QUEEN are of course not set per se. You can use IP addresses or define them in /etc/hosts. So besides eventually filling the hosts file or using the IP addresses and entering in an ssh password there is nothing more to be done to copy files over your network. Of course the computer that you want to copy to must have the sshd server running.

Adding to willysr's example, to copy a folder:
scp -r sourcedir/sourcefolder username@host:/path/to/targetfolder/

Richard Cranium · 04-06-2011, 04:38 AM

Quote:

Originally Posted by EldonCool

I cannot figure out how to copy files over my
network between my two computers.

Does anyone know a good source that tells how to
do this?

I have done it before, but don't remember all the
things I had to go through to do it.

None of the instructional things that I have found
has given me actual instructions that I understand.

Actually I have not even found instructions for
using scp that I can understand. I have all ready
done this in the past, yet with 30 years experience
with computers, a bachelors degree in computer
science, 20 years experience with linux I still
cannot understand anything that I have found that
tells how to do this.

I have two problems.
(1) the actual syntax of scp. None of the instructions
I have found tell what anything is in their examples.

They might say:

scp blah blah yadda yadda zonk zonk.

They don't bother to tell me what blah blah is or
what yadda yadda is, or what zonk zonk is.

(2) Also none of them tells what has to be set up in
configuration files for things to work. For example
one of my computers is named KING, and one is named
QUEEN. There is probably something on computer KING
that tells what QUEEN is. I don't know what this
configuration file is, so of course I can't put in
the entries that would do the job.

So where are some instructions that I might find for
doing this copy of files over my network of two
computers?

The "20 years of experience with linux" is a bit difficult to swallow, since you'd have to have been using it from the very first release to get that. I'm also not sure how you've managed to avoid learning much about TCP/IP in the last 10 years or so.

Not to mention why it never crossed your mind to look at the scp man page via the

Code:

man scp

command.

At any rate, you might want to take a look at what is available here. In particular, you might find The Linux Networking Overview HOWTO, DNS HOWTO, and DHCP mini-HOWTO all to be worth reading. There is other documentation available at the Linux Documentation Project web site.

If you are running Slackware, you can find many of the HOWTOs mentioned at the Linux Documentation Project web site in the directory /usr/doc/Linux-HOWTOs. They are simple ASCII files, so you can use any available editor to read them as well as the "most" and "less" commands.

onebuck · 04-06-2011, 08:56 AM

Hi,

I've been in the Electronic/Computer field for over 40 yrs. Linux experience from the beginning, so ~18 years for Linux. You must have been around when 'SLS' was in development. Look at Linux Distro Timeline to refresh your memory.

My first Linux was Slackware and still is my first choice! I'm not counting 'Minux' or even 'UNIX' experience. Take a look at Rute Tutorial & Exposition plus section 12.2.

I suggest these links to aid you in gaining some understanding;

  1 Linux Documentation Project 
2 Rute Tutorial & Exposition 
3 Linux Command Guide  
4 Bash Beginners Guide 
5 Bash Reference Manual 
6 Advanced Bash-Scripting Guide 
7 Linux Newbie Admin Guide 
8 LinuxSelfHelp 
9 Utimate Linux Newbie Guide
10 Linux Home Networking
11 Virtualiation- Top 10

The above links and others can be found at 'Slackware-Links'. More than just Slackware® links!

EldonCool · 04-06-2011, 04:38 PM

Good description of the command here:

Quote:

scp sourcedir/sourcefile username@host:/path/to/target

I used that as a model and this is a cut and paste of it
with result:

Quote:

>scp /c/ins/ejc.ins joe@queen:/c/ins
ssh: Could not resolve hostname queen: Name or service not known
lost connection

I was on computer "KING" and put the command in to get
the file sent to computer "queen".

As you can see, KING can't figure out who queen is.
This is where I am apparently missing something in setting up
KING configuration.
==================================

Quote:

The "20 years of experience with linux" is a bit difficult to
swallow, since you'd have to have been using it from the very
first release to get that. I'm also not sure how you've managed
to avoid learning much about TCP/IP in the last 10 years or so.

Not to mention why it never crossed your mind to look at the scp
man page via the
Code:

man scp

I have been using linux from the first distributions, almost, which
came on floppy discs. The very first time I used a CD drive I
had to modify code for the CD drives, and compile the kernel to
get my CD drive to work. This was before CD drives were standardized,
and each one then used its own protocall.

Also it did cross my mind to use man scp, but when you do the
resulting verbage can be read with more than one meaning, like:

Quote:

NAME
scp -- secure copy (remote file copy program)

SYNOPSIS
scp [-1246BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file]
[-l limit] [-o ssh_option] [-P port] [-S program]
[[user@]host1:]file1 ... [[user@]host2:]file2

DESCRIPTION
scp copies files between hosts on a network. It uses ssh(1) for
data
transfer, and uses the same authentication and provides the same
security

See the problem here. host1, host2, etc is not defined. Is this
IP address, host name. Also, which is the source and which is the
destination? About as clear as mud isn't it. What does it mean
when it says it "copies files between hosts on a network"? What is
a host? All the people I know call their computers "computers",
not hosts. Since they say hosts, then I am searching again.
Here is what happens when I try to define "host".

Quote:

>man host

gives this man page:

Quote:

HOST(1) BIND9
HOST(1)

NAME
host - DNS lookup utility

SYNOPSIS
host [-aCdlnrsTwv] [-c class] [-N ndots] [-R number] [-t type]
[-W wait] [-m flag] [-4] [-6] {name} [server]

DESCRIPTION
host is a simple utility for performing DNS lookups. It is nor
mally
used to convert names to IP addresses and vice versa. When no
arguments
or options are given, host prints a short summary of its ..
...
...etc.

Real big help isn't it?

And going even further with this cryptic write up in man of
how scp works, You would think they would have at least had
brains enough to specify which was the source computer and
which was the destination of the copy like given in the first
tip on this thread:

Quote:

scp sourcedir/sourcefile username@host:/path/to/target

But no, this is left to guess work, so you don't know if
you are giving the command to:

copy A TO B or copy A from B. so when the command
does not work, you don't know if it did not work because
you have the path names wrong or some other problem.

Quote:

You can use IP addresses or define them in /etc/hosts.

Maybe you can, but I have no clue how to put the IP
address in that command line with scp. Also I have
the problem of "What are my computer IP addresses?"
Also just how do I put them in /etc/hosts?

When I run netstat -nr I get

Quote:

>netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth1

Does any of this tell me my IP address? Is my IP
address something I was supposed to be born knowing?
When I run ifconfig as root, I get:

Quote:

>ifconfig
eth1 Link encap:Ethernet HWaddr 00:50:ba:08:d2:93
inet addr:192.168.0.100 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::250:baff:fe08:d293/64 Scope:Link
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX packets:54888 errors:0 dropped:0 overruns:0 frame:0
TX packets:12005 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:22719374 (21.6 MiB) TX bytes:2609920 (2.4 MiB)
Interrupt:21 Base address:0xe000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

I suppose something here might tell me my "IP address",
but it is not readily apparent to me what that something is.

Also the file /etc/hosts contains this:

Quote:

#
# hosts This file describes a number of hostname-to-address
# mappings for the TCP/IP subsystem. It is mostly
# used at boot time, when no name servers are running.
# On small systems, this file can be used instead of a
# "named" name server. Just add the names, addresses
# and any aliases to this file...
# # By the way, Arnt Gulbrandsen <agulbra@nvg.unit.no> says that 127.0.0.1
# should NEVER be named with the name of the machine. It causes problems
# for some (stupid) programs, irc and reputedly talk. :^)
#

# For loopbacking.
127.0.0.1 localhost
127.0.0.1 KING.King.net KING

# End of hosts.

Okay, you say "You can use IP addresses or define them in /etc/hosts"
Great. Problem is I can't figure out how to do this just looking at
the above contents of hosts. So I use man to help me and I get this
help in how to set up hosts.

Quote:

DESCRIPTION
This manual page describes the format of the /etc/hosts file. This
file is a simple text file that associates IP addresses with hostnames,
one line per IP address. For each host a single line should be present
with the following information:

IP_address canonical_hostname [aliases...]

Fields of the entry are separated by any number of blanks and/or tab
characters. Text from a "#" character until the end of the line is a
comment, and is ignored. Host names may contain only alphanumeric
characters, minus signs ("-"), and periods ("."). They must begin with
an alphabetic character and end with an alphanumeric character.
Optional aliases provide for name changes, alternate spellings, shorter
hostnames, or generic hostnames (for example, localhost).

Maybe you can figure out how to put an entry in the file "hosts"
from this, but it all somehow escapes me.

Quote:

I'm also not sure how you've managed to avoid learning much about TCP/IP in the

That is easy to explain. I have not did much at all with setting up
networks in all my computing. The most I have done is to set up
a computer to get on the internet. I only do this at intervals of
several years in between when I change computers, or internet hardware.

So I am pretty much right where I was to start with, except that
I now know which is the source and which is the destination
with the copy command, thanks to the willysr's first response to
this thread, but no thanks whatever to the man page.

I still have the problem of not being able to do the copy
because, as I said initially:

Quote:

(2) Also none of them tells what has to be set up in
configuration files for things to work. For example
one of my computers is named KING, and one is named
QUEEN. There is probably something on computer KING
that tells what QUEEN is. I don't know what this
configuration file is, so of course I can't put in
the entries that would do the job.

I am thinking that if I could come up with what my computer's
IP addresses were, and for sure what "host" is, that maybe
I could make an entry in /etc/hosts that might define
things. I suspect some environmental variable could tell
me what host is, and sure enough entering:

$HOSTNAME

I get the message: KING.King.net

But still what is my host? Is it KING? Is it KING.King.net?
Is host the same as host name? It seems to me upon setup of
Slackware linux when doing the network it asks me for a host
name, at which time I gave it a name like Ace, King, Queen,
yet hostname environment variables have some other stuff
added on here. In the end, I have no clue which is what, and
man sure does not tell me which is which. Maybe they both
work, but do I really want to set it up using trial and error
just trying things until I magically by accident find the
combination?

I am always left with questions, not answers.

Does anyone yet really understand my problem? If you understand
that I want to know:

(1) how to get my IP address for my computor?
(2) What is a host?
(3) what is a host name?

Then you understand my problem. Can you tell me how to run
any of these down?

onebuck, that long list of things you sent me covered everything
from soup to nuts on linux. I have already been through soup to
nuts. Actually I have even in the past copied from one of my
computers to another. I just can't do it now. I don't want
to start over reading everything in the world on linux. I just
want to copy some files from one computer to another that is
on the same network. I don't need an education in linux in
general. One more thing, so linux came out 18 years ago, big
deal, when I said 20 years experience I pulled a figure off
the top of my head that I thought seemed pretty close. 18 to
20 is close. 17 to 20 is close. I am 73 years old and I am
not wanting to try and pinpoint an exact date for something.
For my purposes when I said 20 years, I think I came damn
close for pulling off the figure, even if it was off two years
that is only 10 percent. Quit nitpicking, and think about my
problem, if you want to help. My problem has now expanded to
defending a statement about how long I have used linux, and
this is getting me no where. If you don't want to bother, that
is acceptable, but I am getting damn tired of people nitpicking
on dates.

pg99 · 04-06-2011, 05:10 PM

This line from ifconfig tells you your ip address
inet addr:192.168.0.100 ...

so the ip address of KING is 192.168.1.100, but if you only want to copy from KING to QUEEN then you don't need to care about KING's ip address, only QUEEN's. So go to QUEEN and type in /sbin/ifconfig and look for the inet addr: line from the eth0,1,2, (whatever, it will be something that starts 192.168.0.xxx on your network)

Once you have that ip address of QUEEN, go back to KING and see if you can connect over ssh - scp uses ssh to transfer, so if you can't connect over ssh, you can't copy any files using scp. Type in
ssh joe@192.168.0.xxx (using the ip address of QUEEN which you just found out)
if it asks you for joe's password, then you're good to go (just cancel out of that ssh, we don't need it anymore now that we know we can connect).

If the ssh worked then you can use the scp command to actually copy the files:
scp /path/to/source joe@192.168.0.xxx:/path/to/dest

If the ssh didn't work, post back and let us know.

Woodsman · 04-06-2011, 08:17 PM

A good idea before testing scp is to first test ssh. The scp command will fail unless ssh is already configured correctly. The ssh daemon must be running too.

If necessary then configure ssh at each computer and start the ssh daemon.

One presumption not stated is that in order for the scp command to be used programmatically, as in a script, the target user at the destination box needs a copy of the source user's public ssh key. That allows passwordless transfers through ssh.

Private keys typically are stored in the sender's $HOME/.ssh/id_dsa and $HOME/.ssh/id_rsa files. Public keys typically are stored in the sender's $HOME/.ssh/id_dsa.pub and $HOME/.ssh/id_rsa.pub files.

To use ssh keys requires a copy of the sender's public key being copied to the recipient's $HOME/.ssh/authorized_keys file.

The scp command is not as robust or flexible as the cp command. For example there is no scp -u option as with cp (update only when newer or missing).

The scp command will push (send) or pull (receive) a file. Typically, the machine at which the user is sitting does not need a user name or host name in the scp command syntax.

To push (send):
scp /full/path/to/find/file root@queen:/full/path/to/save/file

To pull (receive):
scp root@king:/full/path/to/find/file /full/path/to/save/file

When using scp the host name can be a name or an IP address:

scp root@192.168.0.3:/full/path/to/find/file /full/path/to/save/file
scp /full/path/to/find/file root@queen:/full/path/to/save/file

Another presumption is when using a host name that the internal resolver can figure out the actual IP address assigned to that host name. Unless a host name (computer name) is defined somewhere, the resolver will not be able to find the machine. The resolver will actually ask an external DNS name server for help. The simplest method of resolving machine (host) names is using /etc/hosts. The format is like this:

Code:

# IPAddress       Short Name/Alias   Long Name/Hostname
# ---------       ----------------   ------------------
127.0.0.1         localhost          localhost.localdomain
192.168.0.1       router             routername@localdomain   # Local router
192.168.0.2       king               king.localdomain         # His computer
192.168.0.3       queen              queen.localdomain        # Her computer

For small networks, using a hosts file and statically assigning IP address is common. When statically assigning IP addresses, all computers on that same network need the same copy of the hosts file. DHCP becomes more popular when there are many computers involved and maintaining them is cumbersome or impossible. Most ISPs use DHCP because having access to each client's computer is impossible.

When using DHCP, the DHCP server will query each participating box and ask for a host name to match with the dynamically assigned IP address.

EldonCool · 04-06-2011, 09:23 PM

Quote:

This line from ifconfig tells you your ip address
inet addr:192.168.0.100 ...

so the ip address of KING is 192.168.1.100, but if you only want to
copy from KING to queen then you don't need to care about KING's ip
address, only queen's. So go to queen and type in /sbin/ifconfig
and look for the inet addr: line from the eth0,1,2, (whatever, it
will be something that starts 192.168.0.xxx on your network)

Once you have that ip address of queen, go back to KING and see if
you can connect over ssh - scp uses ssh to transfer, so if you can't
connect over ssh, you can't copy any files using scp. Type in
ssh joe@192.168.0.xxx (using the ip address of queen which you
just found out)
if it asks you for joe's password, then you're good to go (just
cancel out of that ssh, we don't need it anymore now that we know
we can connect).

If the ssh worked then you can use the scp command to actually copy
the files:

scp /path/to/source joe@192.168.0.xxx:/path/to/dest

If the ssh didn't work, post back and let us know.

Beautiful!

So I did that command (ssh 192.168.0.100) on queen and
eventually got loged onto KING. So as you said, it works.
I am guessing that ssh means something like secure shell, meaning
you log onto an external computer by some secure means. I may
have done this in the past getting access to another computer
on the internet. Somehow it all seems to make sense.

So far, so good.

Next I did the command

scp joe@192.168.0.100/c/ins/* /c/ins

and sure enough it copied every file from the source directory
to the destination directory. SUCCESS! I can now do it.

Also as I did those commands, the queen system told me:

Quote:

Warning: Permanently added '192.168.0.100' (RSA) to the list
of known hosts.

Lo and behold, after this statement I looked at the file
/etc/hosts on queen and now it has a new entry on the last line,
and that entry is:

Quote:

192.168.0.1 KING

So I did not even have to add it once I did this, the system
did it for me. Also I did not have to know what a host name
was, the system knew, and it turned out to be "KING". One small
detail, leaves me wondering. The address now in /etc/hosts for
KING has 192.168.0.1, yet KING's IP address is 192.168.0.100,
and the warning message said that 192.168.0.100 was added, but
it was not added, 192.168.0.1 was added.

Yet another question, why is this IP address on queen for King
not the same as what King says it is and not the same as what
was said was added? Also, if I change the 192.168.0.100 in the
scp command to KING, will it work? So I try it.

scp joe@KING:/c/ins/ejc.ejc ejc.sit

It don't work. I now get an error message:

ssh: connect to host KING port 22: Connection refused.
So why is the entry in /etc/hosts not working? Is it
because this is only looked at during boot up? Who
knows? But it does not work, it only works if I put
in the IP address.

Another possibility, if I change the entry in /etc/hosts
from

192.168.0.1 KING

to

192.168.0.100 KING

will it work. So I try it.

Yep, it now works, I can do the
command

scp joe@KING:/c/ins/ejc.ejc ejc.sit

and it works, copies the file. Yet
I had to change the entry in /etc/hosts
that the system had put there without
being told to do it, and it put it there
wrong. Things like this can drive a person
nuts. This is suspicious that microsoft
programmers are working on linux systems.
Built in errors like this are a real pain.

Next, I am guessing that if I go onto KING and add this to KING's
/etc/hosts file:

192.168.0.101 queen

then I will be able to copy while working on KING.

I will give it a try.

Yes, it works, I can copy on either machine, but this
was definitely not easy and using man was absolutely
no help in figuring it out.

Also the system has a bug, when it adds this item
to /etc/hosts as it says it does, when it truncates
the last two digits from the IP address.

Anyway, thanks to all for the effort, especially to
pg99. This was the key to get me over the hump.

Also, I got this working before I read Woodsman
reply. I will also try to see if I can understand
that post and add some more understanding. After
I do that, I will give one last post, showing the
main points I have learned and added to my notes.

Thanks to all.

dive · 04-06-2011, 09:30 PM

It doesn't add it to /etc/hosts it adds it to ~/.ssh/known_hosts. You or someone else must have added that line to hosts.

onebuck · 04-07-2011, 08:31 AM

Hi,

Quote:

Originally Posted by EldonCool

<snip>
onebuck, that long list of things you sent me covered everything
from soup to nuts on linux. I have already been through soup to
nuts. Actually I have even in the past copied from one of my
computers to another. I just can't do it now. I don't want
to start over reading everything in the world on linux. I just
want to copy some files from one computer to another that is
on the same network. I don't need an education in linux in
general. One more thing, so linux came out 18 years ago, big
deal, when I said 20 years experience I pulled a figure off
the top of my head that I thought seemed pretty close. 18 to
20 is close. 17 to 20 is close. I am 73 years old and I am
not wanting to try and pinpoint an exact date for something.
For my purposes when I said 20 years, I think I came damn
close for pulling off the figure, even if it was off two years
that is only 10 percent. Quit nitpicking, and think about my
problem, if you want to help. My problem has now expanded to
defending a statement about how long I have used linux, and
this is getting me no where. If you don't want to bother, that
is acceptable, but I am getting damn tired of people nitpicking
on dates.

Apparently you need to read some of that content as you have forgotten basic elements. No one's nitpicking here. The links provided have the information that will aid you to refreshing memory or providing answers to your queries. You are responsible for the system, not I. We are here to aid in the manner that we feel helps.

If your tired of nit-picking on a subject that you initiate then my suggestion is not to present FUD. If you had just read the 12.2 section referred;

Quote:

scp should always be used instead of rcp for security reasons. Notice also the warning given by scp for this first-time connection. See the ssh documentation for how to make your first connection securely. All commands in the ssh package have this same behavior.

Note the underlined above. Then for 'man ssh';

Quote:

ssh (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to
replace rlogin and rsh, and provide secure encrypted communications between two untrusted hosts over an insecure network. X11 con-
nections and arbitrary TCP ports can also be forwarded over the secure channel.

ssh connects and logs into the specified hostname (with optional user name). The user must prove his/her identity to the remote
machine using one of several methods depending on the protocol version used (see below).

If command is specified, it is executed on the remote host instead of a login shell.

The options are as follows:

-1 Forces ssh to try protocol version 1 only.

-2 Forces ssh to try protocol version 2 only.

-4 Forces ssh to use IPv4 addresses only.

-6 Forces ssh to use IPv6 addresses only.

-A Enables forwarding of the authentication agent connection. This can also be specified on a per-host basis in a configuration
file.

Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for
the agent's UNIX-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key
material from the agent, however they can perform operations on the keys that enable them to authenticate using the identi-
ties loaded into the agent.

Quote:

SEE ALSO
scp(1), sftp(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh-keyscan(1), tun(4), hosts.equiv(5), ssh_config(5), ssh-keysign(8),
sshd(8)

'SEE ALSO' provided even more targeted information.

'man hosts' would provide you with;

Quote:

hosts - The static table lookup for hostnames

SYNOPSIS
/etc/hosts

DESCRIPTION
This manual page describes the format of the /etc/hosts file. This file is a simple text file that associates IP addresses with
hostnames, one line per IP address. For each host a single line should be present with the following information:

IP_address canonical_hostname [aliases...]

Fields of the entry are separated by any number of blanks and/or tab characters. Text from a "#" character until the end of the
line is a comment, and is ignored. Host names may contain only alphanumeric characters, minus signs ("-"), and periods (".").
They must begin with an alphabetic character and end with an alphanumeric character. Optional aliases provide for name changes,
alternate spellings, shorter hostnames, or generic hostnames (for example, localhost).

The Berkeley Internet Name Domain (BIND) Server implements the Internet name server for Unix systems. It augments or replaces the
/etc/hosts file or hostname lookup, and frees a host from relying on /etc/hosts being up to date and complete.

In modern systems, even though the host table has been superseded by DNS, it is still widely used for:

bootstrapping
Most systems have a small host table containing the name and address information for important hosts on the local network.
This is useful when DNS is not running, for example during system bootup.

NIS Sites that use NIS use the host table as input to the NIS host database. Even though NIS can be used with DNS, most NIS
sites still use the host table with an entry for all local hosts as a backup.

isolated nodes
Very small sites that are isolated from the network use the host table instead of DNS. If the local information rarely
changes, and the network is not connected to the Internet, DNS offers little advantage.

FILES
/etc/hosts

All the pointed information is at hand for you to discern. You can use 'man command' to understand command information. For someone who claims to have that much experience and not knowing basics of TCP/IP or networking in general then you have forgotten a lot. You have been given information for you to delve into to get the answers. Work for it! Personally, I do not believe in spoon feeding information, you will need to show responsibilities to read the provided information. Then you should be certain that information given is valid.

If your not willing to work and expect someone else to do it for you then maybe getting into Linux wasn't for you.