Linux system problem summary-Update

Summary of linux system problems-Update 1. after creating a new user, switch to the new user: No directory, logging in with HOME =/Add useradd-m-s/bin/bash-g group loginname-m, otherwise, No directory will appear. Logging in with HOME =/)-s/bin/bash uses bash (default:/bin/sh. By default, loginname @ ubuntu is not displayed before $) -g group and then use passwd to change the User Password 2. when deleting a user: userdel: user hbase is currently logged in, there are many solutions on the Internet: mv/var/run/utmp/var/run/utmp_touch>/var/run/utmp about:/var/run/utm Putmp is a file. Except for the utmp program, you cannot edit this file. If you delete it, the current login information will be lost. This file will be re-created every time the machine is reboot. However, I still cannot try it myself. If I still get the same prompt, delete the user brute force: userdel-r-f XXXX: userdel: warning: can't remove/var/mail/git: No such file or directoryuserdel: git home directory (/home/git) not found does not matter. The user has been deleted successfully. Centos1. [las @ gateway1 opt] $ vi/etc/sudoers-bash:/usr/bin/vim: Input/output error the system has a problem, which may be a hardware problem, it cannot be solved temporarily. Change the machine. 2. centos with graphic interface, failed to execute service network restart: Bring up interface eth0: Error: connection activation failed: Device not managed by NetworkManager or ...... the reason is that the network manager is used for network management by default in the graphic interface, and the network is disabled. Run: service NetworkManager stopservice network start. If start is enabled, add chkconfig NetworkManager off chkconfig network on.