Linux boot process, PATH, filter level directory, CD parameters, LS-LRT, command cut logs

 

The second wave of orders is coming to us: start-up process, PATH, filter level directory, CD parameters, LS-LRT, command cut logs

1.1 Linux boot- up process 1.1.1 Post (Bios)--MBRBoot--GRUBMenu-- Load Kernel (Kernel)-- RunINITProcess-- Read/etc/inittabconfiguration file-- Execution/etc/rc.sysinitScripts (init scripts, such as settingsIP,hostname)-- Execution/ETC/RC.D/RC(software that is powered on at run level) script-- Start/sbin/mingettyprocess (Display login interface)

1.2 What is PATH environment variable, what role does it have? 1.2.1 View PATH environment variable

[Email protected] ~]# echo $PATH

/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

1.2.2 PATH function:

1) Environment variables

2) The location of the command is stored

1.2.3 the process of executing a command?

1)ls or mkdir

2) The system will go inside the PATH to find out if the command exists

3) exist on the run

4) Error if not present: Command notfound or no Sush file or directory

1.3 How to filter out the first level directory under the/oldboy directory?

method One: [Email protected] oldboy]# TREE-DL 1

.

├──ext

├──test

├──xiaodong

├──xiaofan

└──xingfujie

Note: 1.-D directory-L equivalent to--level, display up to several levels of directories

Method Two: [Email protected] oldboy]# find-maxdepth 1-type d! -name "."

Note: 1. MaxDepth Deepest

2.! To take the opposite meaning

Method Three: [Email protected] oldboy]# ls-l |grep "^d"

Drwxr-xr-x. 3 root root 4096 Dec 10:35 ext

Drwxr-xr-x. 2 root root 4096 Dec 10:35 test

Note: Find the line that starts with D, the ^ number is used only by three Musketeers, and the regular expression is ... Line starting with

method Four: [Email protected] oldboy]# Ls-l | awk ' $2>1 '

Note:The second line is a $ =

Method Five: [Email protected] oldboy]# ls-f |grep "/"

ext/

test/

Note: -F adds different tags (tails) to different files

1.4 use of the CD command and its options

Note: The CD is an internal command and can be viewed in the manual using man cd or help CD

1.4.1 CD-

[Email protected] oldboy]# CD-

Note: Quickly go back to where you were last

1.4.2 CD.

[[Email protected]/]# CD.

Note: Indicates the current directory

1.4.3 CD..

[Email protected]/]# CD.

Note : Return to the top level directory

1.4.4 CD ~

[Email protected]/]# CD ~

[[Email protected]/]# CD

Note: Enter the current user's host directory, and CD a role

1.5 To View the Help manual:

1)helpCD view internal commands

2)ls--help view external command

3)mancd view full help

Note: Chinese man manual (man.linuxde.net)http://linux.51yip.com/ http://man.linuxde.net/

1.6 how the LS command is displayed in chronological order 1.6.1 When LS is displayed in chronological order

Note: The default is a-Z display

[Email protected] oldboy]# LS-LT

Note:-T is displayed according to the modified time of the file (most recent file on top)

1.6.2 ls displayed in reverse order of time

[Email protected] oldboy]# LS-LRT

Note:-r Displays content in reverse order (including time, letters), latest files at the bottom

1.6.3 ls According to the time of the year/ month / day / hour / minute / display

[Email protected] oldboy]# ls-l--time-style=long-iso

-rw-r--r--. 1 root root 0 2017-12-12 123.txt

1.7 To cut a log by command  Note: You can alsoMonitor the log by software, monitor the size of disk space, etc.1.7.1 Modify the system time

[[email protected] oldboy]# date-s "2017-12-19 11:01:00"

1.7.2 the access log for the Nginx/apache service is logged by day in the server local directory /app/logs/ , which is most required to keep The access log for the last 7 days, how can I resolve it? ( Replace rmwith ls-l first)

1) show Log for 7 days (7)

[Email protected] logs]# Find-type f-mtime 7

2) display logs for the last 7 days (-7)

[Email protected] logs]# find-type f-mtime-7 |xargs ls-l

3) display logs up to 7 days ago (+7)

[Email protected] logs]# find-type f-mtime +7 |xargs ls-l

1.7.3 Find the/aap/logs below with . Log and the modified time is 7 days before the file is deleted (first with ls-l instead)

To create a running environment:

Mkdir-p/app/logs
Cd/app/logs
For time in {01..20};d o date-s "201705$time"; Touch access_www_$ (date +%f). Log;d One
Date-s "20170520"

Workaround:

method One: [Email protected] logs]# Find-type f-mtime +7-exec ls-l {} \;

Method Two: [Email protected] logs]# find-type f-mtime +7 |xargs ls-l

Method Three: [[email protected] logs]# ls-l $ (find-type f-mtime +7)

1.7.4 Debug System service Yes, want to see the/vat/log/secure system Log update in real time, how to do?

[Email protected] logs]# tail-f/var/log/secure

Note:tail-f displays end-of-file updates in real time

1.7.5 Find All files under/oldboy that are larger than 1M at the end of log Copy to / tmp .

method One: [[email protected]/]# CP $ (find/oldboy-type f-size +1024k-name "*.log")/tmp/

Method Two: [Email protected]/]# find/oldboy-type f-size +1024k-name "*.log"-exec cp {}/tmp/\;

Method Three: [Email protected]/]# find/oldboy-type f-size +1024k-name "*.log" |xargs cp-t/tmp/

Note : cp-t reverse copy, put the files to be copied on the last side (normal situation in front)

1.7.6 Merge 2 or more file sizes together

[Email protected] logs]# cat/etc/services/etc/services >/123.log

Note:Cat full name is concatenate, merging the meaning of the associated

Linux boot process, PATH, filter level directory, CD parameters, LS-LRT, command cut logs