Which commands can be used to change the group in a file permission Choose all that apply
Modify File Permissions with chmodThe chmod command allows users to change read and write permissions in Unix systems. In this guide, we will show you how to modify file and directory permissions with chmod. Show
Unix-like systems, including the Linux
systems that run on the Linode platform, have an incredibly robust access control system that allows systems administrators to effectively permit multiple users access to a single system without giving every user access to every file on the file system. The This guide provides a brief overview of file permissions and the operation of the Basics of Linux File PermissionsAll file system objects on Unix-like systems have three main types of permissions: read, write, and execute access. Permissions are bestowed upon three possible classes: the owner, the group, and all other system users. To view the file permissions of a set of files, use:
In the first column of the output, there are 10 characters that represent the permission bits. To understand why they are called permission bits, see the section on octal notation below.
A way to understand the meaning of this column is to divide the bits into groups.
The first character represents the type of file. The remaining nine bits in groups of three represent the permissions for the user, group, and global respectively. Each stands for:
Note that access to files targeted by symbolic links is controlled by the permissions of the targeted file, not the permissions of the link object. There are additional file permissions that control other aspects of access to files. How to Use chmodIn this guide, chmod refers to recent versions of chmod such as those provided by the GNU project. By default, chmod is included with all images provided by Linode, and as part of the common “base” selection of packages provided in nearly all distributions of Linux-based operating systems. Changing File Permissions with chmodTo
change the file permissions using chmod, run In the next few sections, we are going to dive deep into chmod syntax. Using Symbolic Notation Syntax with chmodThe format of a chmod command is:
Consider the following chmod command:
This grants all members of the usergroup that owns the file
The
The parameter Multiple permissions can be specified by separating them with a comma, as in the following example:
This adds write permissions to the usergroup members, and removes read and write permissions from the “other” users of the
system. Finally the In this notation the owner of the file is referred to as the
The Using Octal Notation Syntax with chmodAnother method for setting permissions is through octal notation. Here is example of a file permission that is equivalent to
The permissions for this file are Disregarding the first
bit, each bit that is occupied with a
This is called octal notation because the binary numbers are converted to base-8 by using the digits 0 to 7:
Each digit is independent of the other two. Therefore,
Either notation is equivalent, and you may choose to use whichever form more clearly expresses your permissions needs. Examples of Common Permissions with chmodchmod 600 (rw-------)600 permissions means that only the owner of the file has full read and write access to it. Once a file permission is set to 600, no one else can access the file. Example chmod commands (in octal and symbolic notions) setting permissions to 600:
chmod 664 (rw-rw-r--)664 (
chmod 777 (rwxrwxrwx)chmod 777 is used to grant permissions to everyone to read, write, and execute a file. While using these permissions is a quick way to overcome a permissions-based error, it’s not a best practice for securing most files and applications. Example chmod commands (in octal and symbolic notions) setting permissions to 777:
Making a File ExecutableThe following examples changes the file permissions so that any user can execute the file “~/example.py”:
Restore Default File PermissionsThe default permissions for files on a Unix system are often Issue one of the following chmod commands to reset the permissions on a file back to one of the likely defaults:
For executable files, the equivalent settings would be Use one of the following examples to achieve these executable “default” permissions:
Removing File Permissions with chmodIn order to remove read write permissions given to a file, use the following syntax:
For our file example.txt, we can remove read write permissions using chmod for group by running the following command:
To remove chmod read write permissions from the group while adding read write permission to public/others, we can use the following command:
But, if you wish to remove all permissions for group and others, you can do so using the go= instead:
Restrict File Access: Remove all Group and World PermissionsThere are a number of cases where administrators and users should restrict access to files, particularly files that contain passwords and other sensitive information. The configuration files for msmtp and Fetchmail ( You can remove all access to these files with commands in one of the following forms:
Understanding Linux Directory PermissionsWhile directory permissions within Linux are similar to file permissions, there are a few key differences regarding how these permissions affect user operations:
To view permissions of all files and directories within the working directory, run
Permissions on an individual directory can also be viewed by running How To Change Directory Permissions using chmodDirectory permissions can be adjusted using the same chmod commands as were previously outlined for modifying file permissions. The following example changes permissions on a directory to 755 (owner has read, write and execute permissions, while users with the group or any other user have read and execute permissions):
In many cases, the permissions should also be changed recursively on all
files and subdirectories. This can be done through chmod by using the
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This page was originally published on Thursday, July 1, 2010. Which commands can be used to change the group in a file permission?Change file permissions
To change file and directory permissions, use the command chmod (change mode). The owner of a file can change the permissions for user ( u ), group ( g ), or others ( o ) by adding ( + ) or subtracting ( - ) the read, write, and execute permissions.
How do I change permissions on a file?Login to your computer as an admin. ... . Right-click on the file or folder you want to change permissions and select Properties. ... . Select the Security tab. ... . Select the user you want to modify permissions and then click Edit.. To add a new user or group click on Edit and then Add.. Click Advanced and then Find now.. What is the command to set the execute permissions to all the files?To modify the permission flags on existing files and directories, use the chmod command ("change mode"). It can be used for individual files or it can be run recursively with the -R option to change permissions for all of the subdirectories and files within a directory.
What are the three permission groups for a file?These permissions are categorized into three groups who have or do not have the permissions: the file owner. the owner's group. everyone else who has access to the server (referred to as “other”)
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