RAID disk array
? Redundant array of Inexpensive disks
–redundant Arrays of Inexpensive Disks
– Through hardware/software technology, multiple small/low-speed disks are integrated into one
A large disk
– Value of the array: increased I/O efficiency, hardware-level data redundancy
– Different RAID level features and features vary
? RAID 0, stripe mode
– the same document is distributed across different disks
– Parallel writes for increased efficiency
? RAID 1, mirroring mode
– One document is copied into multiple copies and written to different disks
– Multiple copies for increased reliability and no improvement in efficiency
? RAID5, cost-effective mode
– a compromise equivalent to RAID0 and RAID1
– The capacity of at least one disk is required to hold the checksum data
? RAID6, cost-effective/Reliable mode
– Equivalent to an extended RAID5 array with 2 independent calibration schemes
– The capacity of at least two disks is required to hold the checksum data
? RAID 0+1/raid 1+0
– Benefits of consolidating RAID 0, RAID 1
– Parallel access improves efficiency, mirroring writes improve reliability
? Hard raid: Managed array by raid control card
– Motherboard----> Array card----> Disk----> Operating system----> data
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Process Management
Program: Static code, occupy the space of the hard disk
Process: Dynamic code that takes up memory, CPU space
Parent process/child process
Identification of the process: PID
View process
? Pstree-processes Tree
– Format: pstree [options] [PID or user name]
? Common Command Options
–-a: Displays the full command line
–-p: List the corresponding PID number
SYSTEMD: Parent process for all processes
[Email protected] ~]# Pstree
[Email protected] ~]# Pstree Lisi
Bash───vim
[Email protected] ~]# pstree-p Lisi
Bash (20356) ───vim (20387)
[Email protected] ~]# Pstree-ap Lisi
bash,20356
└─vim,20387 1.txt
###############################################
? PS aux operation
– List all processes that are running
? Ps-elf operation
– List all processes that are running
[[Email protected] ~]# PS aux | Wc-l
131
[Email protected] ~]# Ps-elf | Wc-l
131
[[Email protected] ~]# PS aux
[Email protected] ~]# ps-elf
Process Dynamic Ranking
? Top Interactive tools
– Format: Top [-D refresh seconds] [-u user Name]
[Email protected] ~]# top-d 1
Enter uppercase p to sort by CPU
Enter uppercase M sorted by memory
Enter Q to exit
####################################################
Retrieval process
? Pgrep-process Grep
– Purpose: pgrep [options] ... Query criteria
? Common Command Options
–-l: Output process name, not just PID
–-u: Retrieving the process for a specified user
–-T: Retrieving the process for the specified terminal
–-x: Exact match to Full process name
[Email protected] ~]# Pstree-ap Lisi
bash,22636
└─vim,22669 1.txt
[Email protected] ~]# Pgrep-lu Lisi
22636 Bash
22669 vim
[Email protected] ~]# pgrep-l Crond
[Email protected] ~]# pgrep-l sshd
[Email protected] ~]# pgrep-l log
########################################################
Front and back scheduling of processes
? Background boot
– Add the "&" symbol at the end of the command line without occupying the current terminal
? Ctrl + Z key combination
– Suspends the current process (pauses and goes back into the background)
? Jobs command
– View Background Task List
? FG Command
– Restore background tasks to foreground run
? BG Command
– Activate a task that is suspended from the background
#################################################
[Email protected] ~]# Sleep & #正在运行放入后台
[1] 23304
[[email protected] ~]# jobs
[[email protected] ~]# jobs-l #查看后台进程信息, and output PID
[[email protected] ~]# sleep #按Ctrl +z pause into the background
^z
[2]+ has stopped sleep 700
[Email protected] ~]# jobs-l
[[email protected] ~]# BG 2 #将后台暂停的进程, continue running
[[email protected] ~]# FG 2 #将后台的进程, back to the front desk
[[email protected] ~]# FG 1
#########################################################
Please write the shell script:
The user enters an integer within 10
The computer randomly generates an integer within 10
If two integers are the same, the output is "congratulations, winning."
If two integers are not the same, the output "Congratulations, thank you for your review"
#!/bin/bash
Read-p ' Please enter an integer within 10: ' NUM1
num2=$ (expr $RANDOM% 10)
If [$num 1-eq $num 2];then
Echo, Congratulations, you won the lottery.
Else
Echo Congratulations, thank you for your review
echo the correct number for $num2
Fi
#####################################################
Kill process
? Different ways to kill a process
–ctrl+c key combination to interrupt the current command program
–kill [-9] PID ...
–killall [-9] Process name ...
–pkill Find Criteria
[Email protected]/]# sleep &
[Email protected]/]# sleep &
[Email protected]/]# sleep &
[Email protected]/]# jobs-l
[[email protected]/]# kill 301127
[Email protected]/]# jobs-l
[[email protected]/]# Killall sleep
[Email protected]/]# jobs-l
To force a user to kick out:
[Email protected]/]# killall-9-u Lisi
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Features of the log
? "Journal" of Systems and programs
– Record the various events that occur in the system and program operations
– Understand and troubleshoot by viewing logs
– "Basis" for information security control
? Common Log files
Log file
/var/log/messages record kernel messages, public messages for various services
/VAR/LOG/DMESG recording the various messages of the system startup process
/var/log/cron record messages related to cron scheduled tasks
/var/log/maillog record messages related to sending and receiving mail
/var/log/secure record security messages related to access restrictions
Real-time tracking of new log messages
Tailf
User Login Analysis
? Users, who, W commands
– View logged-in user information with varying degrees of detail
? Last, Lastb command
– View user information for recent login success/failure
[[email protected]/]# users
[email protected]/]# who
[Email protected]/]# W
[Email protected]/]# last-2
[Email protected]/]# lastb-2
################################################
0 Emerg (Emergency) causes the host system to become unusable
1 alert (warning) must take immediate action to solve the problem
2 Crit (severe) more serious situation
3 Err (Error) Run error
4 WARNING (Reminder) events that may affect system functionality
5 NOTICE (note) does not affect the system but is worth noting
6 info (info) General Information
7 Debug (Debug) program or system debug information, etc.
###################################################
Using the Journalctl tool
? Extracting logs collected by the Systemd-journal service
– Mainly includes kernel/system logs, service logs
? Common usage
–journalctl | grep keyword
–journalctl-u service name [-p priority]
–journalctl-n Number of message bars
–journalctl--since= "Yyyy-mm-dd HH:MM:SS"
--until= "Yyyy-mm-dd HH:MM:SS"
[Email protected]/]# journalctl--since= "9:00am"--until= "9:30"
[Email protected]/]# yum-y install httpd
[Email protected]/]# systemctl restart httpd
[Email protected]/]# journalctl-u httpd
[Email protected]/]# Journalctl-n 10
#########################################################
Systemctl Control
Systemd
? A more efficient system & Service Manager
– Start-up service in parallel, precise dependencies between system services
– Configuration directory:/etc/systemd/system/
– Service Catalog:/lib/systemd/system/
– Primary management tool: Systemctl
? Control Service Status
–systemctl Start|stop|restart Service Name ...
? To view the health status of a service
–systemctl status|is-active Service Name ...
Configuring power-on self-booting
? See if the service is self-starting
–systemctl is-enabled Service Name ...
? Set whether the service is booted
–systemctl enable|disable Service Name ...
[Email protected]/]# systemctl status Crond
[Email protected]/]# Systemctl is-active Crond
[Email protected]/]# systemctl restart Crond
[Email protected]/]# Systemctl stop Crond
[Email protected]/]# systemctl status Crond
[Email protected]/]# Systemctl is-active Crond
[Email protected]/]# Systemctl is-enabled Crond
Manage RunLevel (run mode)
Character mode: Multi-user.target
Graphics mode: Graphical.target
View the default run mode
[Email protected]/]# Systemctl Get-default
Set the default run mode
[Email protected]/]# Systemctl set-default graphical.target
[Email protected]/]# Systemctl Get-default
[email protected]/]# reboot
Now enter the appropriate mode immediately
[Email protected]/]# Systemctl isolate Multi-user.target
[Email protected]/]# Systemctl isolate Graphical.target
#####################################################
Linux System Learning 14th Day-<< Engineer Technical >>
