How to solve the problem of accidentally deleting the /root directory in CentOS?

To change the owner of a Linux file, use the chown command. 1. Change the file owner only: sudochownnewuserfilename, for example sudochownlicereport.txt changes the owner of report.txt to alice. 2. Change the owner and group at the same time: sudochownuser:groupfilename, for example, sudochownalice:developersproject.log sets the owner to alice and the group to developers. 3. Change the group only: sudochown:groupfilename, e.g.

Use-Eforextendedregularexpressionstosimplifypatternsyntaxwith ,?,|,and();2.Applywordboundarieswith\borPOSIX[[::]]tomatchwholewords;3.Anchorpatternsusing^and$totargetlinebeginningsandendings;4.Combinemultiplepatternswith|inEREforlogicalORmatching;5.Le

Crontabsyntaxschedulestasksusingfivetimefieldsfollowedbyacommand.1.Firstfieldsetsminutes(0–59).2.Secondfielddefineshours(0–23).3.Thirdfieldspecifiesdayofthemonth(1–31).4.Fourthfielddeterminesthemonth(1–12).5.Fifthfieldindicatesdayoftheweek(0–7,0/7=Su

Installbuildtoolslikebuild-essentialorDevelopmentTools.2.DownloadandextractsourcecodefromarchivesorGit.3.Run./configurewithoptionslike--prefixtosetupthebuild.4.Compileusingmake,optionallywith-j$(nproc)forspeed.5.Installwithsudomakeinstallorusecheckin

To create a temporary alias, you only need to run the alias command in the current session, such as aliasll='ls-la', which will be invalid after closing the terminal; 2. To permanently save the alias, you need to add the alias command to the ~/.bashrc (Bash) or ~/.zshrc (Zsh) file, and run the source command after saving to make the changes take effect immediately; 3. You can use the unalias command to delete the temporary alias, or redefine it to overwrite the existing alias. It is recommended to use meaningful names and avoid overwriting standard commands to maintain the predictability and manageability of the system.

Useiostat-x1tomonitordiskutilization(%util),awaittime,andI/Ooperationspersecond,wherehigh%utilandawaitindicateabottleneck.2.Performaquicksequentialwritespeedtestwithddif=/dev/zeroof=/tmp/testfilebs=1Gcount=1oflag=directstatus=progress,followedbyaread

To effectively manage groups in Linux, you need to master the following 10 steps: 1. Use cat/etc/group, groups or id commands to view existing groups; 2. Use sudogroupaddgroupname to create a new group, and you can specify the GID; 3. Use sudogroupdelgroupname to delete the group, but cannot delete the group that is the main group of the user; 4. Use sudogroupmod-n to modify the group name or -sudogroupmod-g to modify the GID; 5. Use sudousermod-aG or sudogpasswd-a to add the user to the group; 6. Use sudogpasswd-d to remove the user from the group, or use user

Usepasswdusernametosetorchangeauser’spassword,withsudoforotherusers.2.EnforcestrongpasswordsviaPAMbyconfiguring/etc/pam.d/common-passwordwithruleslikeminlen=8,ucredit=-1,lcredit=-1,dcredit=-1,ocredit=-1,difok=3,andremember=5,andsetdefaultsin/etc/logi