1.12. Network commands
1.12.1.write
Send a message to the specified user, end with Ctrl+D to save and send
Send a message to test user as root user
[root@localhost cn]# write test
i missing you.
[root@localhost cn]#
message received by test
[test@localhost ~]$
Message from [email protected] on pts/0 at 21:58 ...
i missing you.
EOF
When this command sends a message, the user must be online to send it, otherwise it will be sent.
You can use w to see which users are online
1.12.2.wall
English willing: write all
send a broadcast message
Syntax: wall [message]
After sending, you will receive a copy
[root@localhost cn]# wall hello world!
[root@localhost cn]#
Broadcast message from [email protected] (pts/0) (Fri Apr 27 22:01:56 2018):
hello world!
The test user also receives a copy
Broadcast message from [email protected] (pts/0) (Fri Apr 27 22:01:56 2018):
hello world!
1.12.3.ping
Test network connectivity
ping option IP address
-c specifies the number of times to send
By default, it will not stop, and it will always send data packets. It must be Ctrl+C to end.
[root@localhost cn]# ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.913 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.54 ms
64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=0.804 ms
64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=0.797 ms
^C
--- 192.168.1.1 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9006ms
rtt min/avg/max/mdev = 0.735/0.947/1.542/0.225 ms
packet loss The packet loss rate is used to judge the network quality.
Use the -c option to specify the number of times to send
[root@localhost cn]# ping -c 2 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.856 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=0.874 ms
--- 192.168.1.1 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.856/0.865/0.874/0.009 ms
[root@localhost cn]#
1.12.4.ifconfig
English original meaning: interface configure
View and set network card information
Syntax: ifconfig network card name IP address
View network card
[root@localhost cn]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.200 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::87e1:e178:41b3:d5b1 prefixlen 64 scopeid 0x20<link>
ether 00:15:5d:01:65:06 txqueuelen 1000 (Ethernet)
RX packets 4592 bytes 859283 (839.1 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1655 bytes 160274 (156.5 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1 (Local Loopback)
RX packets 5 bytes 560 (560.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 5 bytes 560 (560.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo loopback card
RX packets receive data packets and size
TX packets send data packets and size
Set IP, temporary change, non-permanent modification
example:
ifconfig eth0 192.168.1.202
1.12.5.mail
View Send Email
This is better than write in that it does not require the user to be online.
End with Ctrl+D to save and send email
The use of the mail command requires the installation of the mailx installation package
[root@localhost cn]# yum install mailx
Send an email to root user
[root@localhost cn]# mail root
Subject: test subject
hi.
EOT
View sent mail
[root@localhost cn]# mail
Heirloom Mail version 12.5 7/5/10. Type ? for help.
"/var/spool/mail/root": 1 message 1 new
>N 1 root Fri Apr 27 22:18 18/610 "test subject"
N means unread
1 is the ID of the email
root is the sending user
send time
mail title
Enter the mail view interactive command, start the command with &
type help
Can view command help
& help
mail commands
type <message list> type messages
next goto and type next message
from <message list> give head lines of messages
headers print out active message headers
delete <message list> delete messages
undelete <message list> undelete messages
save <message list> folder append messages to folder and mark as saved
copy <message list> folder append messages to folder without marking them
write <message list> file append message texts to file, save attachments
preserve <message list> keep incoming messages in mailbox even if saved
Reply <message list> reply to message senders
reply <message list> reply to message senders and all recipients
mail addresses mail to specific recipients
file folder change to another folder
quit quit and apply changes to folder
xit quit and discard changes made to folder
! shell escape
cd <directory> chdir to directory or home if none given
list list names of all available commands
A <message list> consists of integers, ranges of same, or other criteria
separated by spaces. If omitted, mail uses the last message typed.
&
Enter email ID 1 to view email content
& 1
Message 1:
From [email protected] Fri Apr 27 22:18:17 2018
Return-Path: <[email protected]>
X-Original-To: root
Delivered-To: [email protected]
Date: Fri, 27 Apr 2018 22:18:17 +0800
Subject: test subject
User-Agent: Heirloom mailx 12.5 7/5/10
Content-Type: text/plain; charset=us-ascii
From: [email protected] (root)
Status: R
hi.
&
Enter h to go back to the mailing list
After reading the email, N is not displayed
& h
> 1 root Fri Apr 27 22:18 18/610 "test subject"
&
Enter d mail id, delete mail
& d 1
& h
No applicable messages
&
Enter q to exit
& q
[root@localhost cn]#
1.12.6.last
List all current and past users who have logged into the system, including system restarts
[root@localhost cn]# last
User Login terminal Whether the login IP login time is still online/logout time, duration
test pts/1 192.168.1.101 Fri Apr 27 21:57 still logged in
root pts/0 192.168.1.101 Fri Apr 27 21:20 still logged in
reboot system boot 3.10.0-693.el7.x Fri Apr 27 19:50 - 22:28 (02:37)
test pts / 1 192.168.1.101 Thu Apr 26 23:22 - 23:22 (00:00)
test pts / 1 192.168.1.101 Thu Apr 26 23:07 - 23:22 (00:15)
reboot system boot 3.10.0-693.el7.x Wed Apr 25 21:43 - 22:28 (2+00:45)
root pts/0 192.168.1.101 Tue Apr 24 20:19 - crash (1+01:23)
wtmp begins Sun Apr 22 16:10:16 2018
When the user is listed as reboot, it means the system has restarted.
1.12.7.lastlog
Last login information
List all user information, list the last login information
[root@localhost cn]# lastlog
Username Port From Latest
root pts/0 192.168.1.101 Fri Apr 27 21:20:22 +0800 2018
bin **Never logged in**
daemon **Never logged in**
adm **Never logged in**
lp **Never logged in**
sync **Never logged in**
shutdown **Never logged in**
halt **Never logged in**
mail **Never logged in**
operator **Never logged in**
games **Never logged in**
ftp **Never logged in**
nobody **Never logged in**
systemd-network **Never logged in**
dbus **Never logged in**
polkitd **Never logged in**
postfix **Never logged in**
sshd **Never logged in**
test pts / 1 192.168.1.101 Fri Apr 27 21:57:39 +0800 2018
-u user ID View the login information of a user
[root@localhost cn]# lastlog -u 0
Username Port From Latest
root pts/0 192.168.1.101 Fri Apr 27 21:20:22 +0800 2018
[root@localhost cn]# lastlog -u 1000
Username Port From Latest
test pts / 1 192.168.1.101 Fri Apr 27 21:57:39 +0800 2018
How to check user ID?
[root@localhost cn]# cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
1.12.8.traceroute
Display the path of the packet to the host
This command requires the package traceroute to be installed
[root@localhost cn]# yum install traceroute
[root@localhost cn]# traceroute www.baidu.com
traceroute to www.baidu.com (119.75.213.61), 30 hops max, 60 byte packets
1 gateway (192.168.1.1) 0.525 ms 0.503 ms 1.113 ms
2 * * *
3 * * *
4 10.144.11.202 (10.144.11.202) 1.729 ms 1.720 ms 1.709 ms
5 14.197.242.145 (14.197.242.145) 4.232 ms * 4.900 ms
6 14.197.248.253 (14.197.248.253) 7.647 ms 14.197.248.241 (14.197.248.241) 5.957 ms 14.197.248.253 (14.197.248.253) 6.582 ms
7 14.197.252.197 (14.197.252.197) 45.213 ms 14.197.252.189 (14.197.252.189) 44.424 ms 14.197.252.37 (14.197.252.37) 45.195 ms
8 14.197.252.54 (14.197.252.54) 45.174 ms 45.180 ms 14.197.252.50 (14.197.252.50) 45.170 ms
9 14.197.149.178 (14.197.149.178) 45.162 ms 14.197.149.182 (14.197.149.182) 41.744 ms *
10 * * *
11 * 182.61.253.126 (182.61.253.126) 53.336 ms 42.238 ms
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *
1.12.9.netstat
net status network status
Display network related information
-t TCP protocol, with handshake, confirm receipt.
-u UDP protocol, no handshake, just throw a message in the past, whether you receive it or not
-l listen
-r route
-n show IP address and port number
example:
netstat –tlun View the port that the machine is listening on
[root@localhost cn]# netstat -tlun
Active Internet connections (only servers)
Protocol receiving transmission distance, 0 means normal
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
tcp6 0 0 :::22 :::* LISTEN
tcp6 0 0 ::1:25 :::* LISTEN
[root@localhost cn]#
TCP only listens to LISTEN, UDP does not.
netstat -an View all network connections of the machine
-a all means
[root@localhost cn]# netstat -an
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
tcp 0 0 192.168.1.200:22 192.168.1.101:52591 ESTABLISHED
tcp 0 36 192.168.1.200:22 192.168.1.101:51745 ESTABLISHED
tcp 0 0 192.168.1.200:22 192.168.1.101:52592 ESTABLISHED
tcp 0 0 192.168.1.200:22 192.168.1.101:51748 ESTABLISHED
tcp6 0 0 :::22 :::* LISTEN
tcp6 0 0 ::1:25 :::* LISTEN
raw6 0 0 :::58 :::* 7
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node Path
unix 2 [ ACC ] STREAM LISTENING 19078 public/flush
unix 2 [ ACC ] STREAM LISTENING 19093 public/showq
ESTABLISHED Connected state
netstat –rn View the local routing table
The gateway address can be viewed
[root@localhost cn]# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
[root@localhost cn]#
1.12.10.setup
Configure the network
The set of management tools that comes with red hat does not exist in other versions of Linux.
can support:
Firewall configuration
Network Configuration
system service
Verify configuration
install setuptool
[root@localhost cn]# setup
-bash: setup: command not found
[root@localhost cn]# yum install setuptool
Loaded plugins: fastestmirror
Enter the setup command directly to enter the configuration tool
[root@localhost cn]# setup
1.12.11.mount
mount
mount [-t filesystem] device filename mount point
mount the disc
mount –t iso9660 /dev//sr0 /mnt/cdrom
iso9660
Indicates the CD-ROM file system, this is fixed. The system knows that, in fact, it is not necessary to write.
Device file name, fixed, the CD is /dev/sr0, it can also be specified as a soft link /dev/cdrom
[root@localhost dev]# ll /dev/cdrom
lrwxrwxrwx. 1 root root 3 Apr 27 23:11 /dev/cdrom -> sr0
1. Installation CD
2. Create a mount point
[root@localhost /]# mkdir /mnt/cdrom
3. Mount
[root@localhost dev]# mount /dev/cdrom /mnt/cdrom
mount: /dev/sr0 is write-protected, mounting read-only
[root@localhost dev]#
The prompt message indicates that the CD is read-only and is nearly mounted as a read-only file
You can access it by entering the mount point. /dev/cdrom is a device that cannot be accessed and cannot be accessed.
[root@localhost dev]# cd /mnt/cdrom
[root@localhost cdrom]# ls
autorun.inf boot bootmgr bootmgr.efi efi setup.exe sources support upgrade
[root@localhost cdrom]#
4. Uninstall
In Linux, when you mount and use it, you must manually uninstall it yourself
When the mount point directory is installed, it cannot be uninstalled, and the following prompts: Need to exit the mount point directory
[root@localhost cdrom]# umount /mnt/cdrom
umount: /mnt/cdrom: target is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
[root@localhost cdrom]#
After uninstalling, the contents of the directory /mnt/cdrom are gone.
When unmounting, you can specify the mount point, and you can also specify the device: umount /dev/sr0
[root@localhost /]# umount /mnt/cdrom
[root@localhost /]# ls /mnt/cdrom
[root@localhost /]#