write
explain
Command name: write
Command path / usr/bin/write
Execute permission: all users
Function Description: send information to the user, and save with Ctrl+D
grammar
Example
# Send a message to tenentity
write eternity
[root@izm5e2q95pbpe1hh0kkwoiz ~]# write eternity
write: eternity is logged in more than once; writing to pts/4
hello eternity!!!
[eternity@izm5e2q95pbpe1hh0kkwoiz ~]$
Message from root@izm5e2q95pbpe1hh0kkwoiz on pts/0 at 15:32 ...
hello eternity!!!EOF
wall
explain
Command name: wall
write all
Command path / usr/bin/wall
Execute permission: all users
Function Description: send broadcast information
grammar
vall [message]
Example
# Send broadcast message (it will be received by the user, only the current user can receive it)
wall eternity is a good man!
[root@izm5e2q95pbpe1hh0kkwoiz ~]# wall eternity is a good man!
[root@izm5e2q95pbpe1hh0kkwoiz ~]#
Broadcast message from root@izm5e2q95pbpe1hh0kkwoiz (pts/0) (Thu Dec 5 15:36:18 2019):
eternity is a good man!
[eternity@izm5e2q95pbpe1hh0kkwoiz ~]$
Broadcast message from root@izm5e2q95pbpe1hh0kkwoiz (pts/0) (Thu Dec 5 15:36:18 2019):
eternity is a good man!
ping
explain
Command name: write
Command path / bin/ping
Execute permission: all users
Function Description: test network connectivity
grammar
ping option IP address
-c specify the number of times to sendExample
# Ping 118.190.208.1 (will ping all the time, press ctrl+c to end)
ping 118.190.208.1
[root@izm5e2q95pbpe1hh0kkwoiz ~]# ping 118.190.208.1
PING 118.190.208.1 (118.190.208.1) 56(84) bytes of data.
64 bytes from 118.190.208.1: icmp_seq=1 ttl=64 time=0.201 ms
64 bytes from 118.190.208.1: icmp_seq=2 ttl=64 time=0.207 ms
64 bytes from 118.190.208.1: icmp_seq=3 ttl=64 time=0.161 ms
64 bytes from 118.190.208.1: icmp_seq=4 ttl=64 time=0.197 ms
--- 118.190.208.1 ping statistics ---
8 packets transmitted, 8 received, 0% packet loss, time 7032ms
rtt min/avg/max/mdev = 0.161/0.189/0.218/0.023 ms
# # Ping - C 4 118.190.208.1 (end of Ping 4 times)
ping 118.190.208.1
ifconfig
explain
Command name: ifconfig
Command path / sbin/ifconfig
Execution permission: root
Function Description: view and set network card information
grammar
ifconfig NIC name IP address
Example
# View current computer network card information
ifconfig
# Temporary change of ip address
ifconfig eth0 192.168.1.1
mail
explain
Command name: mail
Command path / bin/mail
Execute permission: all users
Function Description: View send email
grammar
mail command does not exist
yum -y install mailx sendmail
Example
# Send mail to root (ctrl+D)
mail root
[root@izm5e2q95pbpe1hh0kkwoiz ~]# mail root
Subject: test
hello root!!!!
EOT
# View mail
mail
last
explain
Command name: mail
Command path / usr/bin/last
Execute permission: all users
Function Description: list the current and past login user information
grammar
last
Example
# List login information
last
[root@izm5e2q95pbpe1hh0kkwoiz ~]# last
eternity pts/5 123.235.166.172 Thu Dec 5 15:32 still logged in
eternity pts/4 123.235.166.172 Thu Dec 5 15:32 still logged in
root pts/3 123.235.166.172 Thu Dec 5 15:32 still logged in
root pts/2 123.235.166.172 Thu Dec 5 15:32 still logged in
root pts/3 123.235.166.172 Thu Dec 5 15:32 - 15:32 (00:00)
root pts/2 123.235.166.172 Thu Dec 5 15:32 - 15:32 (00:00)
lastlog
explain
Command name: lastlog
Command path / usr/bin/lastlog
Execute permission: all users
Function Description: check the last login time of a specific user
grammar
lastlog options [- u] [uid]
-u user's uidExample
# View last login time
lastlog
[root@izm5e2q95pbpe1hh0kkwoiz ~]# lastlog
Username Port From Latest
root pts/3 123.235.166.172 Thu Dec 5 15:32:14 +0800 2019
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**
chrony **Never logged in**
sshd **Never logged in**
ntp **Never logged in**
tcpdump **Never logged in**
nscd **Never logged in**
mysql **Never logged in**
www **Never logged in**
rabbitmq **Never logged in**
eternity pts/5 123.235.166.172 Thu Dec 5 15:32:17 +0800 2019
saslauth **Never logged in**
mailnull **Never logged in**
smmsp **Never logged in**
# View the last access of the specified user
lastlog -u 502
traceroute
explain
Command name: mail
Command path / bin/traceroute
Execute permission: all users
Function Description: display the path from packet to host
grammar
traceroute
traceroute command does not exist
yum -y install traceroute
Example
# Detect the path to www.baidu.com
traceroute www.baidu.com
[root@izm5e2q95pbpe1hh0kkwoiz ~]# traceroute www.baidu.com
traceroute to www.baidu.com (180.101.49.11), 30 hops max, 60 byte packets
1 * * *
2 11.219.4.81 (11.219.4.81) 5.632 ms 5.931 ms 6.313 ms
3 11.219.4.62 (11.219.4.62) 4.164 ms * 11.219.4.54 (11.219.4.54) 4.114 ms
4 11.219.68.2 (11.219.68.2) 4.848 ms 11.219.68.18 (11.219.68.18) 4.849 ms 11.219.68.2 (11.219.68.2) 4.853 ms
5 103.52.86.106 (103.52.86.106) 1.139 ms 103.52.86.118 (103.52.86.118) 0.536 ms 103.41.143.65 (103.41.143.65) 1.240 ms
6 103.41.143.118 (103.41.143.118) 1.165 ms 116.251.113.221 (116.251.113.221) 0.961 ms 103.41.143.58 (103.41.143.58) 0.963 ms
7 150.138.130.121 (150.138.130.121) 1.618 ms 150.138.130.117 (150.138.130.117) 0.947 ms 0.641 ms
8 150.138.128.161 (150.138.128.161) 8.503 ms 150.138.128.41 (150.138.128.41) 1.928 ms 150.138.128.157 (150.138.128.157) 1.594 ms
9 202.97.19.137 (202.97.19.137) 15.099 ms 202.97.30.129 (202.97.30.129) 13.069 ms 202.97.96.205 (202.97.96.205) 16.943 ms
10 58.213.94.102 (58.213.94.102) 18.576 ms 58.213.94.98 (58.213.94.98) 17.861 ms 58.213.95.102 (58.213.95.102) 17.436 ms
11 * * 58.213.94.86 (58.213.94.86) 18.402 ms
12 58.213.96.94 (58.213.96.94) 21.612 ms 58.213.96.78 (58.213.96.78) 17.852 ms 58.213.96.94 (58.213.96.94) 22.174 ms
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *
netstat
explain
Command name: netstat
Command path: / bin/netstat
Execute permission: all users
Function Description: display network related information
grammar
netstat [options]
-TCP protocol (transmission control protocol)
-u UDP protocol (User Datagram Protocol)
-l monitoring
-r routing
-n display IP address and port numberExample
# View the port the local monitor is listening to
netstat -tlun
# View all network connections on this computer
netstat -an
# View local routing table
netstat -rn
setup
explain
Command name: setup
Command path / usr/bin/setup
Execute permission: all users
Function Description: configure network
grammar
setup
Example
Only the redhat series
Set permanent
mount
explain
Command name: mount
Command path: / bin/mount
Execute permission: all users
Function Description: Mount command
grammar
mount [-t file system] device filename mount point
Example
# Create mount directory first
mkdir /mnt/cdrom
# Mounted CD
mount -t ios9660 /dev/sr0 /mnt/cdrom
-t ios9660 CD file system(Changeless,Omission)
/dev/sr0 Device file name(Changeless,System specified)
/mnt/cdrom Mount point(Mount directory)
# It is also possible to omit - t IOS 9660
mount /dev/sr0 /mnt/cdrom
# Access the data under the CD (that is, the mount directory)
cd /mnt/cdrom
ls
# Uninstall the disc (you must be outside the disc mount directory to uninstall)
umount /dev/sr0
[root@izm5e2q95pbpe1hh0kkwoiz ~]# ll /dev/cdrom
lrwxrwxrwx 1 root root 3 Aug 14 2018 /dev/cdrom -> sr0
/dev/cdrom It's a soft link that points to sr0