Six common commands in Linux system

Ma Nong Online 2021-01-21 14:01:06
common commands linux


crypt

ok , stay Linux System We've been using it all along crypt. seeing the name of a thing one thinks of its function ,crypt It's not an underground palace or a graveyard where junk files are stored , It's a command to encrypt the contents of a file .

Now ,“crypt” Usually implemented as a script : By calling a mcrypt Binary program , Simulate older crypt command , In order to play its role . Use it directly mycrypt A better option .

$ mcrypt xEnter the passphrase (maximum of 512 characters)Please use a combination of upper and lower case letters and numbers.Enter passphrase:Enter passphrase:File x was encrypted.

Please note that :mcrypt The command creates a second file , Its extension is “.nc”.

It doesn't cover the files you're encrypting .mcrypt There are command and encryption algorithm options . You can also specify the key as an option , however mcrypt Orders don't encourage that .

kill

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also kill command —— It's not murder, of course , It's the command we use to terminate the process , How tough the way to terminate depends on what is needed to properly terminate them . Of course ,Linux It doesn't stop there . contrary , It has all kinds of kill Command line for you .

We have kill、pkill、killall、killpg、rfkill、skill( Refer to the es-kill)、tgkill、tkill and xkill.

$ killall runme[1] Terminated ./runme[2] Terminated ./runme[3]- Terminated ./runme[4]+ Terminated ./runme

shred

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Linux The system also supports a system called shred The order of .shred Command to overlay the file to hide the previous contents , And make sure you can't use the hard disk recovery tool to recover them . please remember :rm The command basically just removes the file reference in the directory file , But it's not necessary to erase or overlay content from disk .shred It's the command that covers the contents of the file .

$ shred dupes.txt$ more dupes.txt▒oΛ▒▒9▒lm▒▒▒▒▒o▒1־▒▒f▒f▒▒▒i▒▒h^}&▒▒▒{▒▒

zombies

although zombies( Zombie process ) It's not an order , But it's in Linux It's deeply rooted in the system .zombies It's basically the remains of the death process that haven't been completely removed .

Processes should not run in this way —— Let the process of death linger , Instead of just letting them die 、 Enter the digital paradise , therefore zombies The existence of the shows that there is something wrong with the process that left them .

Check your system for zombie processes , An easy way is to look at top The title line of the command .

It's scary ! It shows three zombie processes .

$ toptop - 18:50:38 up 6 days, 6:36, 2 users, load average: 0.00, 0.00, 0.00Tasks: 171 total, 1 running, 167 sleeping, 0 stopped, 3 zombie <==%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni, 99.9 id, 0.1 wa, 0.0 hi, 0.0 si, 0.0 stKiB Mem : 2003388 total, 250840 free, 545832 used, 1206716 buff/cacheKiB Swap: 9765884 total, 9765764 free, 120 used. 1156536 avail Mem

at midnight

The soul of the dead wanders from sunset to midnight .Linux Let users use “at midnight” Command tracking whether it has left .at It is used to schedule tasks to run when the next specified time comes , It works like a one-time scheduled task (cron).

$ at midnightwarning: commands will be executed using /bin/shat> echo 'the spirits of the dead have left'at> <EOT>job 3 at Thu Oct 31 00:00:00 2017

daemons

Linux The system is also highly dependent on daemons (daemon)—— This process runs in the background , It provides many functions of the system . Many daemons are named with “d” ending . This “d” representative “daemon”, It indicates that the process has been running , Support some important function . Other daemons will “daemon” This word is spelled out .

$ ps -ef | grep sshdroot 1142 1 0 Oct19 ? 00:00:00 /usr/sbin/sshd -Droot 25342 1142 0 18:34 ? 00:00:00 sshd: shs [priv]$ ps -ef | grep daemon | grep -v grepmessage+ 790 1 0 Oct19 ? 00:00:01 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activationroot 836 1 0 Oct19 ? 00:00:02 /usr/lib/accountsservice/accounts-daemon

That's all Liangxu tutorial website For all of you Linux Related knowledge .

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