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    how would a user remove write permissions on file foo.txt for everybody except the owner in linux?

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    Ownership and Permissions

    4.11. Ownership and Permissions

    As a regular user, try to enter root's home directory by entering the command cd /root/. Note the error message:

    -bash: cd: /root/: Permission denied

    That was one demonstration of Linux's security features. Linux, like UNIX, is a multi-user system and file permissions are one way the system protects against malicious tampering.

    One way to gain entry when you are denied permission is to enter the command su -. This is because whoever knows the root password has complete access.

    However, switching to the superuser is not always convenient or recommended, since it is easy to make mistakes and alter important configuration files as the superuser.

    All files and directories are "owned" by the person who created them. You created the file foo.txt (refer to Section 4.9.2 ) in your login directory, so foo.txt belongs to you.

    That means you can specify who is allowed to read the file, write to the file, or (if it is an application instead of a text file) who can execute the file.

    Reading, writing, and executing are the three main settings in permissions. Since users are placed into a group when their accounts are created, you can also specify whether certain groups can read, write to, or execute a file.

    Take a closer look at foo.txt with the ls command using the -l option (refer to Figure 4-11).

    A lot of detail is provided here. You can see who can read (r) and write to (w) the file, as well as who created the file (user), and to which group the owner belongs (user). (By default, the name of your group is the same as your login name.)

    Figure 4-11. Permissions for foo.txt

    Other information to the right of the group includes file size, date and time of file creation, and file name.

    The first column shows current permissions; it has ten slots. The first slot represents the type of file. The remaining nine slots are actually three sets of permissions for three different categories of users.

    For example: -rw-rw-r--

    Those three sets are the owner of the file, the group in which the file belongs, and "others," meaning other users on the system.

    - (rw-) (rw-) (r--) 1 user user

    The first item, which specifies the file type, will probably be one of the following:

    d — a directory

    - (dash) — a regular file (rather than directory or link)

    l — a symbolic link to another program or file elsewhere on the system

    Others are possible, but are beyond the scope of this manual. Refer to the Red Hat Enterprise Linux System Administration Guide for more information.

    Beyond the first item, in each of the following three sets, you may see one of the following:

    r — file can be read

    w — file can be written to

    x — file can be executed (if it is a program)

    - (dash) — specific permission has not been assigned

    When you see a dash in owner, group, or others, it means that particular permission has not been granted. Look again at the first column of foo.txt and identify its permissions.

    ls -l foo.txt

    -rw-rw-r-- 1 user user 150 Mar 19 08:08 foo.txt

    The file's owner (in this case, user) has permission to read and write to the file. The group, user, has permission to read and write to foo.txt, as well. It is not a program, so neither the owner or the group has permission to execute it.

    4.11.1. The chmod Command

    Use the chmod command to change permissions. This example shows how to change the permissions on foo.txt with the chmod command.

    The original file looks like this, with its initial permissions settings:

    -rw-rw-r-- 1 user user 150 Mar 19 08:08 foo.txt

    If you are the owner of the file or are logged into the root account, you can change any permissions for the owner, group, and others.

    Right now, the owner and group can read and write to the file. Anyone outside of the group can only read the file (r--).

    Caution

    Remember that file permissions are a security feature. Whenever you allow anyone else to read, write to, and execute files, you are increasing the risk of files being tampered with, altered, or deleted. As a rule, you should only grant read and write permissions to those who truly need them.

    In the following example, you want to allow everyone to write to the file, so they can read it, write notes in it, and save it. That means you must change the "others" section of the file permissions.

    Take a look at the file first. At the shell prompt, type:

    ls -l foo.txt

    The previous command displays this file information:

    -rw-rw-r-- 1 user user 150 Mar 19 08:08 foo.txt

    Now, type the following:

    chmod o+w foo.txt

    The o+w command tells the system you want to give others write permission to the file foo.txt. To check the results, list the file's details again. Now, the file looks like this:

    -rw-rw-rw- 1 user user 150 Mar 19 08:08 foo.txt

    Now, everyone can read and write to the file.

    To remove read and write permissions from foo.txt use the chmod command to take away both the read and write permissions.

    chmod go-rw foo.txt

    By typing go-rw, you are telling the system to remove read and write permissions for the group and for others from the file foo.txt.

    स्रोत : mirrors.tripadvisor.com

    How Would A User Remove Write Permissions On File For Everybody Except The Owner In Linux — Expert answer

    How would a user remove write permission on a file for everybody except the owner in Linux? txt use the … How Would A User Remove Write Permissions On File For Everybody Except The Owner In Linux — Expert answer Read Article »

    How Would A User Remove Write Permissions On File For Everybody Except The Owner In Linux — Expert answer

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    Table of Contents

    How would a user remove write permission on a file for everybody except the owner in Linux?

    txt use the chmod command to take away both the read and write permissions. By typing go-rw, you are telling the system to remove read and write permissions for the group and for others from the file foo. txt.

    How can we remove the read permission from the owner of a file?

    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 can we delete a file for which we don’t have write permission?

    Just type the password and press Enter and it will delete the files for you. well you have to use the path to your directory .. i dont know what that is so i put an example as to how to do it.

    What does chmod 600 mean?

    Permissions of 600 mean that the owner has full read and write access to the file, while no other user can access the file. Permissions of 644 mean that the owner of the file has read and write access, while the group members and other users on the system only have read access.

    What does chmod 777 mean?

    Setting 777 permissions to a file or directory means that it will be readable, writable and executable by all users and may pose a huge security risk. File ownership can be changed using the chown command and permissions with the chmod command.

    What is the difference between owner and group?

    The idea behind having groups is to give a set of users, like a team of programmers, access to a file. Each file has an owner and a group. The owner is generally the user who created the file. Each user also belongs to a default group, and that group is assigned to every file the user creates.

    How do I change permissions?

    Change app permissions On your phone, open the Settings app. Tap Apps & notifications. Tap the app you want to change. If you can’t find it, first tap See all apps or App info. Tap Permissions. To change a permission setting, tap it, then choose Allow or Deny.

    How do I remove file permissions?

    To remove world read permission from a file you would type chmod o-r [filename]. To remove group read and execute permission while adding the same permission to world you would type chmod g-rx,o+rx [filename]. To remove all permissions for group and world you would type chmod go= [filename].

    How do I turn off user permissions?

    Go to Dashboard > User Management > Users and click the name of the user. Click the Permissions view, then click the trash can icon next to the permission you want to remove, and confirm.

    Does write permission allow delete?

    The Write Attributes permission does not imply creating or deleting files or folders, it only includes the permission to make changes to the attributes of a file or folder.

    How do I remove chmod permissions?

    To change directory permissions in Linux, use the following: chmod +rwx filename to add permissions. chmod -rwx directoryname to remove permissions. chmod +x filename to allow executable permissions. chmod -wx filename to take out write and executable permissions.

    Does Read Write include delete?

    write. Read means you can read it and you can’t change it, to delete requires change.

    What does chmod 555 do?

    What Does Chmod 555 Mean? Setting a file’s permissions to 555 makes it so that the file cannot be modified at all by anyone except the system’s superuser (learn more about the Linux superuser).

    What does chmod 444 mean?

    Here is what the numbers mean: 444 = (r– r– r–): owner/group/others are all only able to read the file. They cannot write to it or execute it. 755 = (rwx r-x r-x): owner can read, write and execute the file, members in the user group and others can read and execute the file but cannot write to it.

    What is the meaning of chmod 775?

    The chmod 775 is an essential command that assigns read, write, and execute permission to a specific user, group, or others.

    How do I get rid of chmod 777?

    Recover from chmod 777 permission on a root filesystem SSH with chmod 777 Permissions. Start to Recover. Booting into Rescue Mode. Chroot to recover. Restore the Permission. SSH with Correct Permission.

    How do I give permission to chmod 777?

    If you are going for a console command it would be: chmod -R 777 /www/store . The -R (or –recursive ) options make it recursive. chmod -R 777 .

    What does chmod 700 mean?

    chmod 700 file Protects a file against any access from other users, while the issuing user still has full access.

    What is the difference between owner and group in Linux?

    Every Linux system have three types of owner: All the users belonging to a group have same access permission for a file. Other: Any one who has access to the file other than user and group comes in the category of other.

    Who are others in Linux?

    2 Answers. Others is not technically a group. Other is everyone that is not the owner or in the group. For example, if you have a file that is root:root then root is the owner, users/processes in the root group have group permissions, and you are treated as other.

    स्रोत : techproland.com

    Technology Tips: chmod overview

    The chmod (CHange MODe) command is used to change permissions for a file or directory on a Unix machine. For example, let's say you've downloaded a piece of software you want to share with other people on your system. If the file is large it would be a waste of resources to have everyone who wanted to use the software download their own copy. It would be much better to have

    Technology Tips: chmod overview

    Marvin Crippen, DO-IT technology assistant

    The chmod (CHange MODe) command is used to change permissions for a file or directory on a Unix machine. For example, let's say you've downloaded a piece of software you want to share with other people on your system. If the file is large it would be a waste of resources to have everyone who wanted to use the software download their own copy. It would be much better to have one person download the software and change the permissions so everyone on that system could access the file. Or perhaps you've uploaded some software and you need to change the file permission so you can run it.

    Finding the current permissions

    Typing ls -ld at the host system prompt will show you the permissions of your home directory, with a string of 10 characters that should look something like drwx------ or drwx--x--x. The first character is what type of entry you're looking at, either d for directory or - for a plain file. The rest of the characters are broken up into fields of three. The first set of three represent the owners permissions, the second set of three represent the group permissions (the use of group permissions varies from system to system. They are not generally used on UW Uniform Access systems), and the third set of three representing the "other" permissions. The "other" category encompasses everyone else and is usually called world, which I will use for the rest of this article. The first character of each set represents read (r) which allows read access to the file. The second character of each set represents write (w) which allows changes to be made to the file, including deletion. The third character of each set represents execute (x) which allows running the file. A dash (-) in any entry means no permission for that operation. So, the first example of the ls -ld command (drwx---------) means the entry is a directory in which the owner has read, write and execute permissions and no one else has any permissions. The second example of the ls -ld command (drwx--x--x) is a directory (it happens to be my home directory on Hawking) in which the owner has read, write, and execute permissions, the group has execute permissions and everyone else (world) has execute permissions.

    How to change permissions

    The format of the chmod command is chmod [permission] [filename]. The permission can be specified in either the symbolic or absolute mode. In the symbolic mode you must specify three things. One, who to change the permission for; owner (u), group (g) and/or world (o). Two, what kind of change to make to the permission; add permission (+), remove permission (-) or exclusive permission (=) add that permission and remove all other permissions. Three, what permission; read (r), write (w) and/or execute (x). To add world read and execute permission to a file using the symbolic mode you would type chmod o+rx [filename]. To remove world read permission from a file you would type chmod o-r [filename]. To remove group read and execute permission while adding the same permission to world you would type chmod g-rx,o+rx [filename]. To remove all permissions for group and world you would type chmod go= [filename].

    Sound a bit complex? There is an alternative. All you have to do is remember a couple of numbers and you can use the absolute mode to change permission. The absolute mode uses 3 numbers to represent the permission. To remove all permissions for group and world you would type chmod 700 [filename]. To give the owner all permissions and world execute you would type chmod 701 [filename]. To give the owner all permissions and world read and execute you would type chmod 705 [filename]. The absolute mode functions like the exclusive permission of the symbolic mode in that it exclusively sets the permission specified removing all other permissions. For more information on how to use the absolute mode, including how to figure out the numbers see the absolute mode section of the chmod man page (man chmod).

    Absolute vs. Symbolic

    Which method you use is a matter of personal preference; use whatever you feel most comfortable with. In general the symbolic mode is easier for making small modifications such as adding world execute to files that already have world read. Absolute mode is easier for making large modifications such as removing all world and group permissions.

    Now What?

    There are just a couple more steps to go in order to let other users access your files. First off you need to give world execute permission for your root directory using the command chmod o+x ~. For your root directory execute is safer than execute and read. See Important Notes for why. Second you need to change the permissions for the files you want other users to be able to access, including any directories along the way. Since sub directories generally do not have as much important information as your root directory giving sub directories world read and execute permissions is not as big a security risk. If I wanted to give everyone on Hawking access to the file ~mcrip/World/hello.world, I would use the following three commands from my root directory:

    स्रोत : www.washington.edu

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