What are the three ways to properly edit the ETC Group Files select three?
The /etc/group file contains basic group attributes. This is an ASCII file that contains records for system groups. Each record appears on a single line and is the following format: Show
Name:Password:ID:User1,User2,...,Usern You must separate each attribute with a colon. Records are separated by new-line characters. The attributes in a record have the following values: AttributeDescriptionNameSpecifies a group name that is unique on the system. See the mkgroup command for information on the restrictions for naming groups.PasswordNot used. Group administrators are provided instead of group passwords. See the /etc/security/group file for more information.IDSpecifies the group ID. The value is a unique decimal integer string. The maximum value is 4,294,967,295 (4 GB).User1,User2,...,UsernIdentifies a list of one or more users. Separate group member names with commas. Each user must already be defined in the local database configuration files. Do not use a : (colon) in any of the attribute fields. For an example of a record, see the "Examples" section . Additional attributes are defined in the /etc/security/group file. Note: Certain system-defined group and user names are required for proper installation and update of the system software. Exercise care before replacing the /etc/group file to ensure that no system-supplied groups or users are removed. You should access the /etc/group file through the system commands and subroutines defined for this purpose. You can use the following commands to manage groups:
To change the Name parameter, you first use the mkgroup command to add a new entry. Then, you use the rmgroup command to remove the old group. To display all the attributes in the file, use the lsgroup command. You can use the chgroup, chgrpmem, or chuser command to change all user and group attributes. The mkuser command adds a user whose primary group is defined in the /usr/lib/security/mkuser.default file and the rmuser command removes a user. Although you can change the group ID with the chgroup command, this is not recommended. The following table lists all the possible group names and what functions the group controls. Group nameDescriptionsystemThis group is used for configuration and maintenance for hardware and software.printqThis group is used for managing queuing functions such as, enable, disable, qadm, and qpri.securityThis group is used for handling password and limits control.admThis group is used for monitoring functions such as, performance, cron, and accounting.staffThis group is the default group assigned to all new users.auditThis group is used for auditing.shutdownThis group allows users access to the shutdown command.binThis group is used for the system internal group.sysThis group is used for the system internal group.uucpThis group manages the UUCP system.mailThis group allows users to access the mail command.cronThis group allows users to access the crontab command.nobodyThis group is for user that do not owns any files and can be used as the default user for unprivileged operations.kmemThis group allows users virtual memory read and write access such as, /dev/mem, /dev/port, and /dev/kmem.logThis group allows users access to log files in /var/log.lpThis group allows users access to the lp command.networkThis group allows users access to use the NetworkManager functions such as NM-Applet and KNetwrokmanager.powerThis group allows users access to suspend power.rootThis group allows users access to all system functions.ttyThis group allows users access to serial and USB devices.usersThis group is the default users group. This is the recommended group name you should use for users. SecurityAccess Control: This file should grant read (r) access to all users and grant write (w) access only to the root user and members of the security group. ExamplesA typical record looks like the following example for the staff group:
In this example, the GroupID parameter is 1 and the users are defined to be shadow and cjf. FilesItemDescription/etc/groupContains basic group attributes./etc/security/groupContains the extended attributes of groups./etc/passwdContains the basic attributes of users./etc/security/passwdContains password information./etc/security/userContains the extended attributes of users./etc/security/environContains the environment attributes of users./etc/security/limitsContains the process resource limits of users./etc/security/audit/configContains audit system configuration information. Linux is a clone of UNIX, the multi-user operating system which can be accessed by many users simultaneously. Linux can also be used in mainframes and servers without any modifications. But this raises security concerns as an unsolicited or malign user can corrupt, change or remove crucial data. For effective security, Linux divides authorization into 2 levels.
In this Linux file commands tutorial, you will learn-
The concept of Linux File permission and ownership is crucial in Linux. Here, we will explain Linux permissions and ownership and will discuss both of them. Let us start with the Ownership. Click here if the video is not accessible Linux File OwnershipEvery file and directory on your Unix/Linux system is assigned 3 types of owner, given below. UserA user is the owner of the file. By default, the person who created a file becomes its owner. Hence, a user is also sometimes called an owner. GroupA user- group can contain multiple users. All users belonging to a group will have the same Linux group permissions access to the file. Suppose you have a project where a number of people require access to a file. Instead of manually assigning permissions to each user, you could add all users to a group, and assign group permission to file such that only this group members and no one else can read or modify the files. OtherAny other user who has access to a file. This person has neither created the file, nor he belongs to a usergroup who could own the file. Practically, it means everybody else. Hence, when you set the permission for others, it is also referred as set permissions for the world. Now, the big question arises how does Linux distinguish between these three user types so that a user ‘A’ cannot affect a file which contains some other user ‘B’s’ vital information/data. It is like you do not want your colleague, who works on your Linux computer, to view your images. This is where Permissions set in, and they define user behavior. Let us understand the Permission system on Linux. Linux File PermissionsEvery file and directory in your UNIX/Linux system has following 3 permissions defined for all the 3 owners discussed above.
Let’s see file permissions in Linux with examples: ls – l on terminal gives ls - l Here, we have highlighted ‘-rw-rw-r–‘and this weird looking code is the one that tells us about the Unix permissions given to the owner, user group and the world. Here, the first ‘–‘ implies that we have selected a file.p> Else, if it were a directory, d would have been shown. The characters are pretty easy to remember. r = read permission Let us look at it this way. The first part of the code is ‘rw-‘. This suggests that the owner ‘Home’ can:
By design, many Linux distributions like Fedora, CentOS, Ubuntu, etc. will add users to a group of the same group name as the user name. Thus, a user ‘tom’ is added to a group named ‘tom’. The second part is ‘rw-‘. It for the user group ‘Home’ and group-members can:
The third part is for the world which means any user. It says ‘r–‘. This means the user can only:
Changing file/directory permissions in Linux Using ‘chmod’ commandSay you do not want your colleague to see your personal images. This can be achieved by changing file permissions. We can use the ‘chmod’ command which stands for ‘change mode’. Using the command, we can set permissions (read, write, execute) on a file/directory for the owner, group and the world. Syntax: chmod permissions filename There are 2 ways to use the command –
Absolute(Numeric) Mode in LinuxIn this mode, file permissions are not represented as characters but a three-digit octal number. The table below gives numbers for all for permissions types. NumberPermission TypeSymbol0 No Permission — 1 Execute –x 2 Write -w- 3 Execute + Write -wx 4 Read r– 5 Read + Execute r-x 6 Read +Write rw- 7 Read + Write +Execute rwx Let’s see the chmod permissions command in action. In the above-given terminal window, we have changed the permissions of the file ‘sample to ‘764’. ‘764’ absolute code says the following:
This is shown as ‘-rwxrw-r– This is how you can change user permissions in Linux on file by assigning an absolute number. Symbolic Mode in LinuxIn the Absolute mode, you change permissions for all 3 owners. In the symbolic mode, you can modify permissions of a specific owner. It makes use of mathematical symbols to modify the Unix file permissions. OperatorDescription+ Adds a permission to a file or directory – Removes the permission = Sets the permission and overrides the permissions set earlier. The various owners are represented as – User Denotationsu user/owner g group o other a all We will not be using permissions in numbers like 755 but characters like rwx. Let’s look into an example Changing Ownership and Group in LinuxFor changing the ownership of a file/directory, you can use the following command: chown user filename In case you want to change the user as well as group for a file or directory use the command chown user:group filename Let’s see this in action In case you want to change group-owner only, use the command chgrp group_name filename ‘chgrp’ stands for change group. Tip
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Guru99 is Sponsored by Acunetix Acunetix, the developers of dead-accurate web application security scanners have sponsored the Guru99 project to help scan for over 4500 web vulnerabilities accurately and at top speed. What is used to specify a group ID?-g, –gid GID : This option is used to provide a group id (numeric) to the new group, and it should be non-negative and unique unless explicitly created to be non-unique (using -o option). If this option is not used, the default id is assigned, which is greater than every other group already present.
What commands would grant additional users access to use the sudo command quizlet?You need to add an administrator to the /etc/sudoers file to give them the ability to use the sudo command.
What command can an administrator use to change the password of an existing user account in quizlet?Chmod (Change Mode) allows the user to change the access (mode) of a file to read, write, execute, or a combination of those permissions. The passwd (password) command is used to change a Linux user's password. The chown (Change Owner) command is used to modify the file owner or group owner assignment.
What are the types of user accounts in Linux quizlet?User Account. the mechanism by which the Linux OS is able to handle the task of protection.. Protection. ... . In Linux, there are three forms of user accounts: ... . Root Account. ... . User Account. ... . Software Account. ... . /etc/passwd. ... . /etc/gshadow.. |