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linux:managing-users-and-groups-part-1
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linux:managing-users-and-groups-part-1 [2019/01/21 11:14] seanburns created |
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| - | < | ||
| - | # Managing Users and Groups | ||
| - | ## Date: Mon Sep 24 12:17:52 EDT 2018 | ||
| - | ## The passwd file | ||
| - | |||
| - | On my Fedora 28 virtual machine, I can see the following information about my user account: | ||
| - | |||
| - | ```bash | ||
| - | $ grep " | ||
| - | sean: | ||
| - | ``` | ||
| - | |||
| - | The fields are: | ||
| - | |||
| - | - username | ||
| - | - password indicator | ||
| - | - user id | ||
| - | - group id | ||
| - | - gecos ingo | ||
| - | - home directory | ||
| - | - default shell | ||
| - | |||
| - | This is a pretty standard Linux file, but some things will change | ||
| - | depending on the distribution. For example, the user id may start at a | ||
| - | different point depending on the system. However, nowadays both Ubuntu | ||
| - | and Fedora set the starting UID and group ID for new users at 1000. | ||
| - | |||
| - | ## The shadow file | ||
| - | |||
| - | Need to be root to examine the shadow file: | ||
| - | |||
| - | ```bash | ||
| - | $ sudo su | ||
| - | # grep " | ||
| - | sean: | ||
| - | ``` | ||
| - | |||
| - | The fields are: | ||
| - | |||
| - | - login name (username) | ||
| - | - encrypted password | ||
| - | - days since 1/1/1970 since password was last changed | ||
| - | - days after which password must be changed | ||
| - | - days before password is to expire that user is warned | ||
| - | - days after password expires that account is disabled | ||
| - | - days since 1/1/1970 that account is disabled | ||
| - | - a reserved field | ||
| - | |||
| - | ## The group file | ||
| - | |||
| - | This file holds group information about the entire system: | ||
| - | |||
| - | ```bash | ||
| - | $ cat /etc/group | ||
| - | $ # note one group of interest | ||
| - | $ grep " | ||
| - | project1: | ||
| - | ``` | ||
| - | |||
| - | The fields are: | ||
| - | |||
| - | - group name | ||
| - | - group password | ||
| - | - group ID (GID) | ||
| - | - group members | ||
| - | |||
| - | ## Management Tools | ||
| - | |||
| - | The book discusses the following tools: | ||
| - | |||
| - | - */ | ||
| - | - */ | ||
| - | - */ | ||
| - | - */ | ||
| - | - */ | ||
| - | - */ | ||
| - | |||
| - | ## Practice | ||
| - | |||
| - | ### Create a new user; modify account | ||
| - | |||
| - | Let's create a new user and modify the account. First note the defaults | ||
| - | in **/ | ||
| - | And then let's change some defaults. We can either user *sudo* or | ||
| - | become *su*. Here I become *su*: | ||
| - | |||
| - | ```bash | ||
| - | $ sudo su | ||
| - | # nano / | ||
| - | ``` | ||
| - | |||
| - | Now we're in *nano*, and we want to add these lines at the end. Feel free to add the comments: | ||
| - | |||
| - | ```bash | ||
| - | # make " | ||
| - | alias c=' | ||
| - | # new files are 600; new directories are 700: | ||
| - | umask 0077 | ||
| - | ``` | ||
| - | |||
| - | Now use *nano* again to create a README file. This file will be added to the home directories of all new users. Add any welcome message you want to add, plus any guidelines for using the system. | ||
| - | |||
| - | ```bash | ||
| - | # nano / | ||
| - | ``` | ||
| - | |||
| - | After writing (saving) and exiting *nano*, we can go ahead and create the new user: | ||
| - | |||
| - | ```bash | ||
| - | # useradd linus | ||
| - | # grep " | ||
| - | linus: | ||
| - | # grep " | ||
| - | linus: | ||
| - | # # Let's create a password for ' | ||
| - | # passwd linus | ||
| - | # grep " | ||
| - | # # Let's modify the maximum password lifetime | ||
| - | # passwd -n 90 linus | ||
| - | # # Let's modify the maximum password lifetime | ||
| - | # passwd -x 180 linus | ||
| - | ``` | ||
| - | |||
| - | ### Create a new group; add users to group | ||
| - | |||
| - | ```bash | ||
| - | # grep " | ||
| - | # groupadd project2 | ||
| - | # grep " | ||
| - | project2: | ||
| - | # usermod -aG project2 linus | ||
| - | # usermod -aG project2 sean | ||
| - | # grep " | ||
| - | project2: | ||
| - | ``` | ||
| - | |||
| - | ### Delete, delete, delete | ||
| - | |||
| - | 1. Delete user ' | ||
| - | 2. Confirm not listed in **passwd** and **shadow** files. | ||
| - | 3. Confirm home directory is gone | ||
| - | |||
| - | #### User deletion | ||
| - | |||
| - | ```bash | ||
| - | # userdel -r linus | ||
| - | # grep " | ||
| - | # grep " | ||
| - | # cd /home ; ls -l | ||
| - | ``` | ||
| - | |||
| - | #### Group deletion | ||
| - | |||
| - | 1. Look for groups in **group** file that begin with the string | ||
| - | " | ||
| - | 2. Delete " | ||
| - | 3. Look again. | ||
| - | |||
| - | ```bash | ||
| - | # grep " | ||
| - | # groupdel project2 | ||
| - | # grep " | ||
| - | ``` | ||
| - | </ | ||
linux/managing-users-and-groups-part-1.1548087296.txt.gz ยท Last modified: 2019/01/21 11:14 by seanburns
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