FILE transfer and sync update

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# download files/apps: wget [args] [URL]

# continue the paused downloading mission: wget -c [mission_name]

# scp (Secure copy) copy file from one computer to another
# scp source_file destination_file 
# file can be represented with user@ip:file_name
[mo@mos-computer ~]$ scp name.txt root@192.168.0.120:/root
name.txt                                      100%   12     6.5KB/s   00:00  

# copy from another computer to this computer:
[mo@mos-computer ~]$ scp root@192.168.0.120:/root/name.txt file_changed_name.txt
name.txt                                      100%   12     6.9KB/s   00:00 

[mo@mos-computer ~]$ ls
... file_changed_name.txt

# change the port number: scp -p [port_num]

# ftp & sftp: download from public/private FTP server

# -p means passive mode
[mo@mos-computer ~]$ ftp -p ftp.fr.debian.org
Trying 212.27.32.66...
Connected to ftp.fr.debian.org (212.27.32.66).
220 Welcome to french Debian FTP server
Name (ftp.fr.debian.org:mo): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
227 Entering Passive Mode (212,27,32,66,88,25).
150 Here comes the directory listing.
drwxr-xr-x    9 1000     1000         4096 Mar 10 08:25 debian
drwxr-xr-x    8 1000     1000         4096 Mar 01  2015 debian-amd64
drwxr-sr-x    5 1000     1000          102 Mar 13  2016 debian-backports
drwxr-xr-x    6 1000     1000          143 Mar 10 04:00 debian-non-US
drwxr-xr-x    7 1000     1000          142 Mar 09 21:22 debian-security
drwxr-sr-x    5 1000     1000          138 Nov 01  2011 debian-volatile
drwxr-xr-x    2 1000     1000            6 Mar 09 23:00 tmp
226 Directory send OK.
ftp> pwd
257 "/"
ftp> cd debian
250 Directory successfully changed.
ftp> ls
227 Entering Passive Mode (212,27,32,66,42,172).
150 Here comes the directory listing.
-rw-r--r--    1 1000     1000         1190 Feb 06 09:19 README
-rw-r--r--    1 1000     1000         1290 Jun 26  2010 README.CD-manufacture
-rw-r--r--    1 1000     1000         2900 Feb 06 09:19 README.html
-rw-r--r--    1 1000     1000          291 Mar 04  2017 README.mirrors.html
-rw-r--r--    1 1000     1000           86 Mar 04  2017 README.mirrors.txt
drwxr-xr-x   19 1000     1000         4096 Feb 06 09:21 dists
drwxr-xr-x    4 1000     1000         4096 Mar 10 07:52 doc
-rw-r--r--    1 1000     1000       205133 Mar 10 08:15 extrafiles
drwxr-xr-x    3 1000     1000         8192 Mar 10 08:10 indices
-rw-r--r--    1 1000     1000     13533572 Mar 10 08:10 ls-lR.gz
drwxr-xr-x    5 1000     1000           62 Dec 19  2000 pool
drwxr-xr-x    4 1000     1000           67 Nov 17  2008 project
drwxr-xr-x    3 1000     1000           77 Oct 10  2012 tools
drwxr-xr-x   20 1000     1000         4096 Jul 07  2019 zzz-dists
226 Directory send OK.
# download the README file
ftp> get README
local: README remote: README
227 Entering Passive Mode (212,27,32,66,222,243).
150 Opening BINARY mode data connection for README (1190 bytes).
226 Transfer complete.
1190 bytes received in 1.71 secs (0.70 Kbytes/sec)
ftp> !ls
compression	       myFIle		   rar
Desktop		       name_sorted.txt	   rarlinux-x64-5.7.0.tar.gz
Documents	       name.txt		   README
Downloads	       newfile		   redirect
errors.log	       new_folder	   repeat.txt
file_changed_name.txt  newly_created_file  results.txt
file-copy.txt	       node		   Templates
grep_log	       nohup.out	   test
htop-2.2.0	       number.txt	   unique.txt
htop-2.2.0.tar.gz      output_find	   Videos
Music		       Pictures
myFile		       Public
# upload file
ftp> put name.txt
local: name.txt remote: name.txt
227 Entering Passive Mode (212,27,32,66,82,83).
550 Permission denied.
ftp> 
# Ctrl d to exit
ftp> 221 Goodbye.

# sftp (secure) use -oProt to change the port
# rsync: remote synchronize, very useful in sync files on two devices
# -arv   a: adding r:recursive v:verbose

# further reading: how to use rsync to write backup file...

Network Security

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# IPv4 and IPv6 addresses, hostname (www.), domainname(xxx.com), DNS
[root@mos-computer mo]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
13.229.188.59 github.com

# you can customize some hosts couples to access specific websites, this works for local network
[root@mos-computer mo]# whois github.com
   Domain Name: GITHUB.COM
   Registry Domain ID: 1264983250_DOMAIN_COM-VRSN
   Registrar WHOIS Server: whois.markmonitor.com
   Registrar URL: http://www.markmonitor.com
   Updated Date: 2020-09-08T09:18:27Z
   Creation Date: 2007-10-09T18:20:50Z
   Registry Expiry Date: 2022-10-09T18:20:50Z
   Registrar: MarkMonitor Inc.
   Registrar IANA ID: 292
   Registrar Abuse Contact Email: abusecomplaints@markmonitor.com
   Registrar Abuse Contact Phone: +1.2083895740
   Domain Status: clientDeleteProhibited https://icann.org/epp#clientDeleteProhibited
   Domain Status: clientTransferProhibited https://icann.org/epp#clientTransferProhibited
   Domain Status: clientUpdateProhibited https://icann.org/epp#clientUpdateProhibited
   Name Server: DNS1.P08.NSONE.NET
   Name Server: DNS2.P08.NSONE.NET
   Name Server: DNS3.P08.NSONE.NET
   Name Server: DNS4.P08.NSONE.NET
   Name Server: NS-1283.AWSDNS-32.ORG
   Name Server: NS-1707.AWSDNS-21.CO.UK
   Name Server: NS-421.AWSDNS-52.COM
   Name Server: NS-520.AWSDNS-01.NET
   DNSSEC: unsigned
   URL of the ICANN Whois Inaccuracy Complaint Form: https://www.icann.org/wicf/
>>> Last update of whois database: 2021-03-10T13:35:54Z <<<

For more information on Whois status codes, please visit https://icann.org/epp

NOTICE: The expiration date displayed in this record is the date the
registrar's sponsorship of the domain name registration in the registry is
currently set to expire. This date does not necessarily reflect the expiration
date of the domain name registrant's agreement with the sponsoring
registrar.  Users may consult the sponsoring registrar's Whois database to
view the registrar's reported date of expiration for this registration.

TERMS OF USE: You are not authorized to access or query our Whois
database through the use of electronic processes that are high-volume and
automated except as reasonably necessary to register domain names or
modify existing registrations; the Data in VeriSign Global Registry
Services' ("VeriSign") Whois database is provided by VeriSign for
information purposes only, and to assist persons in obtaining information
about or related to a domain name registration record. VeriSign does not
guarantee its accuracy. By submitting a Whois query, you agree to abide
by the following terms of use: You agree that you may use this Data only
for lawful purposes and that under no circumstances will you use this Data
to: (1) allow, enable, or otherwise support the transmission of mass
unsolicited, commercial advertising or solicitations via e-mail, telephone,
or facsimile; or (2) enable high volume, automated, electronic processes
that apply to VeriSign (or its computer systems). The compilation,
repackaging, dissemination or other use of this Data is expressly
prohibited without the prior written consent of VeriSign. You agree not to
use electronic processes that are automated and high-volume to access or
query the Whois database except as reasonably necessary to register
domain names or modify existing registrations. VeriSign reserves the right
to restrict your access to the Whois database in its sole discretion to ensure
operational stability.  VeriSign may restrict or terminate your access to the
Whois database for failure to abide by these terms of use. VeriSign
reserves the right to modify these terms at any time.

The Registry database contains ON
LY .COM, .NET, .EDU domains and
Registrars.

# eth0 : wired network connections, ehthernet ,lo: Local loopback, wlan0: wireless connection.
# You may noticed that some of those names changed, that was because new CentOS version
# use 'systemd' to replace the 'initd' to guide the system. e.g. enp0s3 --> eth0

# Network Analysis
ifconfig interface state

# you can shutdown/ open some specific connection
[root@mos-computer mo]# ifconfig ens33 down
[root@mos-computer mo]# ping 192.168.0.120
connect: Network is unreachable
[root@mos-computer mo]# ifconfig ens33 up
[root@mos-computer mo]# ping 192.168.0.120
PING 192.168.0.120 (192.168.0.120) 56(84) bytes of data.
64 bytes from 192.168.0.120: icmp_seq=1 ttl=128 time=0.783 ms
64 bytes from 192.168.0.120: icmp_seq=2 ttl=128 time=0.691 ms
64 bytes from 192.168.0.120: icmp_seq=3 ttl=128 time=0.624 ms
64 bytes from 192.168.0.120: icmp_seq=4 ttl=128 time=0.703 ms
^C
--- 192.168.0.120 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3001ms
rtt min/avg/max/mdev = 0.624/0.700/0.783/0.059 ms

# Network data
[root@mos-computer mo]# netstat
# interface info: MTU : max transmute unit DRP: drop num OVR: drop because override ... 
[root@mos-computer mo]# netstat -i
Kernel Interface table
Iface             MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
ens33            1500    10287      0      0 0          2384      0      0      0 BMRU
lo              65536       39      0      0 0            39      0      0      0 LRU
virbr0           1500        0      0      0 0             0      0      0      0 BMU
# udp, tcp (and other protocol) data
[root@mos-computer mo]# netstat -uta
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 mos-computer:domain     0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:ssh             0.0.0.0:*               LISTEN     
tcp        0      0 localhost:ipp           0.0.0.0:*               LISTEN     
tcp        0      0 localhost:smtp          0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:sunrpc          0.0.0.0:*               LISTEN     
tcp6       0      0 [::]:ssh                [::]:*                  LISTEN     
tcp6       0      0 localhost:ipp           [::]:*                  LISTEN     
tcp6       0      0 localhost:smtp          [::]:*                  LISTEN     
tcp6       0      0 [::]:sunrpc             [::]:*                  LISTEN     
udp        0      0 0.0.0.0:34360           0.0.0.0:*                          
udp        0      0 mos-computer:domain     0.0.0.0:*                          
udp        0      0 0.0.0.0:bootps          0.0.0.0:*                          
udp        0      0 0.0.0.0:bootpc          0.0.0.0:*                          
udp        0      0 0.0.0.0:sunrpc          0.0.0.0:*                          
udp        0      0 localhost:323           0.0.0.0:*                          
udp        0      0 0.0.0.0:929             0.0.0.0:*                          
udp        0      0 0.0.0.0:mdns            0.0.0.0:*                          
udp6       0      0 [::]:sunrpc             [::]:*                             
udp6       0      0 localhost:323           [::]:*                             
udp6       0      0 [::]:929                [::]:*                             
# only UDP info
[root@mos-computer mo]# netstat -ua
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
udp        0      0 0.0.0.0:34360           0.0.0.0:*                          
udp        0      0 mos-computer:domain     0.0.0.0:*                          
udp        0      0 0.0.0.0:bootps          0.0.0.0:*                          
udp        0      0 0.0.0.0:bootpc          0.0.0.0:*                          
udp        0      0 0.0.0.0:sunrpc          0.0.0.0:*                          
udp        0      0 localhost:323           0.0.0.0:*                          
udp        0      0 0.0.0.0:929             0.0.0.0:*                          
udp        0      0 0.0.0.0:mdns            0.0.0.0:*                          
udp6       0      0 [::]:sunrpc             [::]:*                             
udp6       0      0 localhost:323           [::]:*                             
udp6       0      0 [::]:929                [::]:* 

# Port: 80 for HTTP, 21 for FTP, 110 for POP3
# LISTEN connection
[root@mos-computer mo]# netstat -lt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 mos-computer:domain     0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:ssh             0.0.0.0:*               LISTEN     
tcp        0      0 localhost:ipp           0.0.0.0:*               LISTEN     
tcp        0      0 localhost:smtp          0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:sunrpc          0.0.0.0:*               LISTEN     
tcp6       0      0 [::]:ssh                [::]:*                  LISTEN     
tcp6       0      0 localhost:ipp           [::]:*                  LISTEN     
tcp6       0      0 localhost:smtp          [::]:*                  LISTEN     
tcp6       0      0 [::]:sunrpc             [::]:*                  LISTEN     
# Summary
[root@mos-computer mo]# netstat -s
Ip:
    2496 total packets received
    0 forwarded
    0 incoming packets discarded
    2308 incoming packets delivered
    2343 requests sent out
    8 outgoing packets dropped
    71 dropped because of missing route
Icmp:
    23 ICMP messages received
    0 input ICMP message failed.
    ICMP input histogram:
        destination unreachable: 18
        echo requests: 1
        echo replies: 4
    24 ICMP messages sent
    0 ICMP messages failed
    ICMP output histogram:
        destination unreachable: 19
        echo request: 4
        echo replies: 1
IcmpMsg:
        InType0: 4
        InType3: 18
        InType8: 1
        OutType0: 1
        OutType3: 19
        OutType8: 4
Tcp:
    24 active connections openings
    0 passive connection openings
    0 failed connection attempts
    2 connection resets received
    0 connections established
    2131 segments received
    2072 segments send out
    3 segments retransmited
    0 bad segments received.
    5 resets sent
Udp:
    136 packets received
    18 packets to unknown port received.
    0 packet receive errors
    241 packets sent
    0 receive buffer errors
    0 send buffer errors
UdpLite:
TcpExt:
    16 TCP sockets finished time wait in fast timer
    15 delayed acks sent
    Quick ack mode was activated 1 times
    26 packets directly queued to recvmsg prequeue.
    6737 bytes directly received in process context from prequeue
    1705 packet headers predicted
    21 packets header predicted and directly queued to user
    26 acknowledgments not containing data payload received
    79 predicted acknowledgments
    3 congestion windows recovered without slow start after partial ack
    3 other TCP timeouts
    2 connections reset due to early user close
    TCPRcvCoalesce: 43
    TCPAutoCorking: 4
    TCPSynRetrans: 3
    TCPOrigDataSent: 107
IpExt:
    InNoRoutes: 4
    InMcastPkts: 141
    OutMcastPkts: 44
    InBcastPkts: 42
    InOctets: 13875424
    OutOctets: 123651
    InMcastOctets: 14149
    OutMcastOctets: 8425
    InBcastOctets: 4182
    InNoECTPkts: 10306