Introduction to the essence of linux creation users and the essence of linux Creation

Introduction to the essence of linux creation users and the essence of linux Creation

Ref: manually create a user in the/etc/default/useradd configuration file/etc/skel directory of the useradd command

Parameters of the useradd command

[Vincent @ localhost ~] $ Useradd -- help-bash:/usr/sbin/useradd: Permission denied [vincent @ localhost ~] $ Sudo useradd -- help [sudo] password for vincent: Usage: useradd [options] LOGIN useradd-D [options] Options:-B, -- base-dir BASE_DIR base directory for the home directory of the new account-c, -- comment comment gecos field of the new account-d, -- home-dir HOME_DIR home directory of the new account # It can be seen that this parameter can print the default configuration file-D when adding a user, -- defaults print or change default useradd configuration -E, -- expiredate EXPIRE_DATE expiration date of the new account-f, -- inactive INACTIVE password inactivity period of the new account-g, -- gid GROUP name or ID of the primary group of the new account-G, -- groups GROUPS list of supplementary groups of the new account-h, -- help display this help message and exit-k, -- skel SKEL_DIR use this alternative skeleton directory-K, -- key KEY = VALUE overr Ide/etc/login. defs defaults-l, -- no-log-init do not add the user to the lastlog and faillog databases-m, -- create-home create the user's home directory-M, -- no-create-home do not create the user's home directory-N, -- no-user-group do not create a group with the same name as the user-o, -- non-unique allow to create users with duplicate (non-unique) UID-p, -- password PASSWORD encrypted passwo Rd of the new account-r, -- system create a system account-R, -- root CHROOT_DIR directory to chroot into-s, -- shell SHELL login shell of the new account-u, -- uid UID user ID of the new account-U, -- user-group create a group with the same name as the user-Z, -- selinux-user SEUSER use a specific SEUSER for the SELinux user mapping # view the default configuration when adding a user [vincent @ localhost ~] $ Sudo useradd-DGROUP = 100 HOME =/homeINACTIVE =-1 EXPIRE = SHELL =/bin/bashSKEL =/etc/skelCREATE_MAIL_SPOOL = yes [vincent @ localhost ~] $ Sudo useradd-D-s/sbin/nologin # In fact, the output above is the content in the/etc/default/useradd file] $ sudo cat/etc/default/useradd # useradd defaults fileGROUP = 100 HOME =/homeINACTIVE =-1 EXPIRE = SHELL =/sbin/nologinSKEL =/etc/skelCREATE_MAIL_SPOOL = yes

/Etc/default/useradd configuration file

That is, the source of output result printed by useradd-D.

Files in the/etc/skel directory

Files under this directory will be copied to the new user's home directory when creating a user, provided that this user has a home directory

The directory tree is as follows:

[vincent@localhost ~]$ sudo ls -la /etc/skel/total 24drwxr-xr-x.  2 root root   59 Mar 22 11:14 .drwxr-xr-x. 74 root root 8192 Mar 22 13:47 ..-rw-r--r--.  1 root root   18 Nov 20  2015 .bash_logout-rw-r--r--.  1 root root  193 Nov 20  2015 .bash_profile-rw-r--r--.  1 root root  231 Nov 20  2015 .bashr

Create a user manually

1. Create a home directory for the user

$ sudo mkdir /home/annie[sudo] password for vincent: 

2. copy the files used for logon and logout to the new user directory.

[vincent@localhost ~]$ sudo ls /etc/skel/ -a.  ..  .bash_logout  .bash_profile  .bashrc[vincent@localhost ~]$ sudo cp /etc/skel/.bash_logout  /etc/skel/.bashrc /etc/skel/.bash_profile /home/annie/

3. Modify related configuration files

/Etc/passwd

$ grep annie /etc/passwdannie:x:1001:1001:vincent:/home/annie:/bin/bash

/Etc/shadow

$ sudo grep annie /etc/shadow annie:$6$PiTiKh9B$Da4VaaR0qlk55r1VFyX3OfQfgj944xExTIdAsyVVTqjmf/u.On8MAfkV0B9RQg5E/OzWj2nYEHGnX.M8feXE3/:17612:0:99999:7:::

/Etc/group

$ sudo grep annie /etc/group annie:x:1001:annie

4. Change the password and test logon.

[vincent@localhost ~]$ sudo passwd annie Changing password for user annie.New password: BAD PASSWORD: The password is shorter than 8 charactersRetype new password: passwd: all authentication tokens updated successfully.[vincent@localhost ~]$ [vincent@localhost ~]$ [vincent@localhost ~]$ su - annie Password: Last failed login: Thu Mar 22 17:26:18 EDT 2018 on pts/1There was 1 failed login attempt since the last successful login.[annie@localhost ~]$ [annie@localhost ~]$ id uid=1001(annie) gid=1001(annie) groups=1001(annie)[annie@localhost ~]$ who am i vincent  pts/1        2018-03-22 17:23 (172.16.81.1)[annie@localhost ~]$ id annie uid=1001(annie) gid=1001(annie) groups=1001(annie)[annie@localhost ~]$ logout