Common commands and skills in Liunx system Management
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Common commands for linux to view hardware equipment and system information
1. System
The code is as follows:
# uname-a # View kernel / operating system / CPU information
# head-n 1 / etc/issue # View operating system version
# cat / proc/cpuinfo # View CPU information
# hostname # View computer name
# lspci-tv # list all PCI devices
# lsusb-tv # list all USB devices
# lsmod # list the loaded kernel modules
# env # View environment variables
2. Common commands for resource viewing
The code is as follows:
# free-m # View memory usage and swap area usage
# df-h # View the usage of each partition
# du-sh # View the size of the specified directory
# grep MemTotal / proc/meminfo # check the total memory
# grep MemFree / proc/meminfo # check the amount of free memory
# uptime # View system running time, number of users, and load
# cat / proc/loadavg # View system load
2. Common commands for disk and partition
The code is as follows:
# mount | column-t # to view the status of attached partitions
# fdisk-l # View all partitions
# swapon-s # View all swap partitions
# hdparm-I / dev/hda # View disk parameters (for IDE devices only)
# dmesg | grep IDE # check the detection status of IDE devices at startup
4. Commands commonly used in network management
The code is as follows:
# ifconfig # View the properties of all network interfaces
# iptables-L # View firewall settings
# route-n # View the routing table
# netstat-lntp # View all listening ports
# netstat-antp # View all established connections
# netstat-s # View network statistics
5. Common commands related to process
The code is as follows:
# ps-ef # View all processes
# top # Real-time display of process status
6. User-related common commands
The code is as follows:
# w # View active users
# id # View specified user information
# last # View user login log
# cut-d:-F1 / etc/passwd # View all users of the system
# cut-d:-F1 / etc/group # View all groups of the system
# crontab-l # View the current user's scheduled tasks
6. Service
The code is as follows:
# chkconfig-list # list all system services
# chkconfig-list | grep on # lists all started system services
7. Programs, software
The code is as follows:
# rpm-qa # View all installed packages
2. Use iptables to shield IP segments under linux:
Shield a single IP
The code is as follows:
Iptables-I INPUT-s 124.115.0.199-j DROP
Mask IP segment
The code is as follows:
Iptables-I INPUT-s 124.115.0 DROP 16-j
Iptables-I INPUT-s 124.115.3.0 Universe 16-j DROP
Iptables-I INPUT-s 124.115.4.0 Universe 16-j DROP
Block the entire IP segment
The code is as follows:
Iptables-I INPUT-s 124.115.0 DROP 8-j
Block several IP segments
The code is as follows:
Iptables-I INPUT-s 61.37.80.0 DROP 24-j
Iptables-I INPUT-s 61.37.81.0 DROP 24-j
Don't forget to save and restart the iptables service after execution. The above is how to use iptables to mask IP segments under Linux.
Unseal
The code is as follows:
Iptables-D INPUT-s 14.153.250.80 DROP 24-j
Iptables-D INPUT-s 14.153.250.80-j DROP
Prohibit all IP from accessing a port
The code is as follows:
Iptables-I INPUT-p TCP-dport 80-j DROP
3. Several methods for quickly emptying the contents of files:
The code is as follows:
$: > filename # where: is a placeholder and does not produce any output.
$> filename
$echo "" > filename
$echo / dev/null > filename
$echo > filename
$cat / dev/null > filename
At some point, you need to empty the contents of the file without deleting the file. For example, some log files (log.txt)
The command under linux is: true > log.txt
Test results:
The code is as follows:
Touch log.txt → # New File log.txt
Vi log.txt → # Editing File
Enter anything you want.
: wq! Enter → # Save exit
Cat log.txt → # View file contents
True > log.txt → # View the contents of the file
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