How To Use chmod and chown Command

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How do I use chmod and chown command under Linux / Unix operating systems?

Use the chown command to change file owner and group information. we run the chmod command command to change file access permissions such as read, write, and access. This page explains how to use chmod and chown command on Linux or Unix-like systems.

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Understanding file permissions for chmod and chown command

One can use file permissions to control access to their files. Sysadmins can enforce a security policy based upon file permissions. All files have three types:

  1. Owner – Person or process who created the file.
  2. Group – All users have a primary group, and they own the file, which is useful for sharing files or giving access.
  3. Others – Users who are not the owner, nor a member of the group. Also, know as world permission.

read (r), write (w), and execute (x) permission

We can set the following permissions on both files and directories:

PermissionFileDirectory
rReading access/view fileUsers can read file. In other words, they can run the ls command to list contents of the folder/directory.
wWriting access/update/remove fileUsers can update, write and delete a file from the directory.
xExecution access. Run a file/script as commandUsers can execute/run file as command and they have r permission too.
-No access. When you want to remove r, w, and x permissionAll access is taken away or removed.

Please note that permission priority decided as follows by the kernel:
User permissions -> Group permissions -> Other permissions
It means user permission overrides group permission and group permissions overrides other permission.

Viewing Linux/Unix file permissions and ownership

Run the ls command:
ls -l
# Show information about a file named file1 #
ls -l file1
ls -l /path/to/file1
# Get information about a directory named dir1 #
ls -ld dir1
ls -l -d /path/to/dir1

For example, we can list permissions for /etc/hosts and /etc/ directory as follows:
ls -l /etc/hosts
Pass the -d option to ls to list directories themselves, not their contents:

-rw-r--r-- 1 root root 742 Jul  1 14:39 /etc/host

ls -l -d /etc/

drwxr-xr-x 175 root root 12288 Jul 30 08:53 /etc

From above outputs it is clear that the first character indicate the file type in drwxr-xr-x and -rw-r–r– and the next 9 characters are the actual file permissions.

rw-r–r– file and drwxr-xr-x directory permission explained

First characterDescription
-Regular file.
bBlock special file.
cCharacter special file.
dDirectory.
lSymbolic link.
pFIFO.
sSocket.
wWhiteout.

Next nine characters are the file permissions divided into three sets/triad of three characters for owner permissions, group permissions, and other/world permissions as follows:

Three permission triads defined what the user/group/others can doFirst triad defines what the owner can doSecond triad explains what the group members can doThird triad defines what other users can do
-rw-r--r--Owner has only read and write permission (rw-)Group has read permission (r--)Others has read permission (r--)
drwxr-xr-xOwner has full permission (rwx)Group has read and execute permission (r-x)Others has read and execute permission (r-x)

Displaying file permission using the stat command

Run the following command:
stat file1
stat dir1
stat /etc/passwd
stat /etc/resolv.conf

  File: /etc/passwd
  Size: 3100      	Blocks: 8          IO Block: 4096   regular file
Device: fd02h/64770d	Inode: 25954314    Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-07-29 23:09:01.865822913 +0530
Modify: 2020-07-02 19:16:43.743727913 +0530
Change: 2020-07-02 19:16:43.747727898 +0530
 Birth: -

GUI displaying file permissions:
Chmod and Chown in GUI

chown command

The chown command changes the user and/or group ownership of for given file. The syntax is:

chown owner-user file 
chown owner-user:owner-group file
chown owner-user:owner-group directory
chown options owner-user:owner-group file

Examples

First, list permissions for demo.txt, enter:
# ls -l demo.txt
Sample outputs:

-rw-r--r-- 1 root root 0 Aug 31 05:48 demo.txt

In this example change file ownership to vivek user and list the permissions, run:
# chown vivek demo.txt
# ls -l demo.txt

Sample outputs:

-rw-r--r-- 1 vivek root 0 Aug 31 05:48 demo.txt

In this next example, the owner is set to vivek followed by a colon and a group onwership is also set to vivek group, run:
# chown vivek:vivek demo.txt
# ls -l demo.txt

Sample outputs:

-rw-r--r-- 1 vivek vivek 0 Aug 31 05:48 demo.txt

In this example, change only the group of file. To do so, the colon and following GROUP-name ftp are given, but the owner is omitted, only the group of the files is changed:
# chown :ftp demo.txt
# ls -l demo.txt

Sample outputs:

-rw-r--r-- 1 vivek ftp 0 Aug 31 05:48 demo.txt

Please note that if only a colon is given, or if NEW-OWNER is empty, neither the owner nor the group is changed:
# chown : demo.txt
In this example, change the owner of /foo to “root”, execute:
# chown root /foo
Likewise, but also change its group to “httpd”, enter:
# chown root:httpd /foo
Change the owner of /foo and subfiles to “root”, run:
# chown -R root /u
Where,

  • -R – Recursively change ownership of directories and their contents.

chmod command

The syntax is:
chmod permission file
chmod permission dir
chmod UserAccessRightsPermission file

We use the following letters for user:

  • u for user
  • g for group
  • o for others
  • a for all

We can set or remove (user access rights) file permission using the following letters:

  • + for adding
  • - for removing
  • = set exact permission

File permission letter is as follows:

  • r for read-only
  • w for write-only
  • x for execute-only

Now we can use the symbolic method for changing file permissions based upon the above letters.

Examples

Delete read and write permission for group and others on a file named config.php:
$ ls -l config.php
# State 'who' : g (group) and o (others)
# State what to do with 'who': - (remove)
# State permissions for 'who': r (read) and w (write)

$ chmod -v go-rw config.php
$ ls -l config.php
$ stat config.php

How to use chown command on Linux and Unix
Let us adds read permission for all/everyone (a). In other words, give read permission to user, group and others:
$ chmod a+r file.pl
Delete execute permission for all everyone (a):
$ chmod a-x myscript.sh
Adds read and execute permissions for everyone (a):
$ chmod a+rx pager.pl
Next, sets read and write permission for user, sets read for group, and remove all access for others:
$ chmod u=rw,g=r,o= birthday.cgi
In this file example, sets read and write permissions for user and group:
$ chmod ug=rw /var/www/html/data.php
See “how to use change user rights using chomod command” for more information.

Conclusion

We explained the chown and chmod command for Linux and Unix users. I strongly suggest that you read man pages by typing the following man command or see GNU coreutils online help pages:
man chown
man chmod

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.


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33 comment

  1. don’t know where you got this but all you get is an error that the directory does not exist. so if this script is working for you, then your server is set up wrong and you are riding or borrowed time.

  2. Good lesson as far as it goes. However:
    This command will only work if the file targeted by the command exists. You can’t change ownership of a non-existent file!

  3. Hello,

    I am Hitesh, i am a S/W Engineer, My nickname is CSD.
    Linux is useless operating system.

    I am the owner of Tata Magic IRIS. I don’t need this command to change anything.
    I am the ROOT.

    You all people are FOOL.

    1. Hello,

      I am Hitesh, i am ID10T who uses everybody’s valuable oxygen.
      Intelligence is useless concept me.

      I am the owner of pathetic little car. I don’t have anything contribute to site.
      I am the MORON.

      You all people are TOOL.

      In other words: if you don’t understand proper english, don’t try to act like you do, you little numpty.

  4. What if I want to give permission to everyone
    /home/storage
    I need it so anyone who access from a windows share via network neighborhood can read and write to this directory from any location

    Robert

  5. Hi, Kc5jmr.
    The chmod and chown commands are really for use to fine-tune permissions among users of a single filesystem [–usually, but not always, a single computer with multiple users.].

    What you’re talking about is setting up a Samba [SMB] fileserver for network sharing of files. That is really a whole different project from just adjusting file permissions for various logged-in users on the same machine!

    I use Samba to access files on my desktop workhorse from my portable computer. Setting up a Samba server and writing a config file that specifies the directories to be shared is not all that difficult.

    BUT SMB was a Windows protocol devised in the middle 1980’s. To the best of my understanding, Windows 7 uses some other setup. All I know is that my Win7 OS on my portable can’t connect to my Linux samba server, but booting the same machine in Mepis Linux allows me full access. Since I only boot into Win7 to play “Sid Meyer’s Civilization” [versions IV & V] the lack of backward compatibility to SMB/Samba really doesn’t affect me enough for me to bother to try to get Win7 to play nice. I do all my serious work in Linux, and only have so much time/energy for gratuitous MS-Windows troubleshooting!

  6. Hitesh, don’t comment here you obviously no nothing about system administration.

    And if your using a development system\environment that “requires” a root account so your can write software your the FOOL.

  7. Hi Guys

    can anyone assist, i am getting an error when trying to start one of my applications on my linux server.

    ./pwcallmgr: error while loading shared libraries: libjs.so: cannot restore segment prot after reloc: Permission denied

  8. you have over written the permissions because these instructions were poorly written open up your Terminal navigate tothe root file system and add yourself as a user allowed to open this file… having followed these instructions with teh recursive you have possibly told your OS that only root can open that file when you need to be the one who does. use grep to find the for or just type in find ./pwcallmgr once you have this file chown yourusername ./pwcallmgr if it says not permitted the sudo chown yourusername ./pwcallmgr should do it.

    Be very careful when using the -Recursive switch or you could end up having to boot using a live disk to fix this …. and make your computer unbootable…
    You can also use Chmod 777 if you need to however you should check what file permissions that file is supposed to have.

    Of course if you have a full back up on another drive of your .hidden files and your home file along with any other files you like to keep then it can be faster just to reinstall with the latest OS…. but I would back things up just in case and try the chown first ….

  9. Thanks, as i always prefer this website in the case of unix commands or scripts.

    Thanks to this website.

    As i get the 100% correct solutions.

  10. “chown -R” frightens me. When I’m admin’ing I’m often needed to change the ownership of files owned by “bob” to “bill” in filesystems with files owned by a number of accounts.

    I would typically (from memory):

    find . -user bob -exec chown bill {} \;

  11. Hello. At the last line of this guide where you have “/u” did you possibly mean “/foo” ??
    To be consistent, perhaps this is what you rather meant?

  12. I have directory ‘/u02/Infa_shared’, created one group ‘Developers’ and Added users ‘A’,’B’. Owner of this directory is ‘infaadmin’ and user belongs to ‘admin’ group.

    How can I give read, write, execute access on this directory to ‘Developers’ by keeping ‘admin’ group has its owner in Linux?

  13. i have one doubt, any one help me. i have created one parent directory (sample). that directory owner is “test”, now i created many sub directories under sample. now i want changed sub directory owner.
    Note : No changes to parent directory.

  14. i have pasted a directory(grid folder) from windows 10 into may Linux machine

    [root@localhost Desktop]# cd /u01
    [root@localhost u01]# ls
    grid lost+found
    [root@localhost u01]# cd grid
    [root@localhost grid]# ls
    install response runcluvfy.sh sshsetup welcome.html
    readme.html rpm runInstaller stage
    [root@localhost grid]# ls -l
    total 68
    drwxr-xr-x. 4 root root 4096 Nov 24 00:45 install
    -rw-r–r–. 1 root root 30016 Aug 26 2013 readme.html
    drwxr-xr-x. 2 root root 4096 Nov 24 00:45 response
    drwxr-xr-x. 2 root root 4096 Nov 24 00:45 rpm
    -rw-r–r–. 1 root root 4878 Aug 26 2013 runcluvfy.sh
    -rw-r–r–. 1 root root 3268 Aug 26 2013 runInstaller
    drwxr-xr-x. 2 root root 4096 Nov 24 00:45 sshsetup
    drwxr-xr-x. 14 root root 4096 Nov 24 00:48 stage
    -rw-r–r–. 1 root root 500 Aug 26 2013 welcome.html

    now i wanna run the runInstaller to Install it but i can’t what can i do ????

    and i can’t access my shared folder from windows to linux through vmware i have enabled the folder for sharing but when i type

    [root@localhost Desktop]# df -h
    Filesystem Size Used Avail Use% Mounted on
    /dev/sda1 20G 5.3G 13G 30% /
    tmpfs 1002M 224K 1002M 1% /dev/shm
    /dev/sda3 35G 1.3G 32G 4% /u01
    /dev/sr0 3.7G 3.7G 0 100% /media/OL6.5 x86_64 Disc 1 20131125
    [root@localhost Desktop]#

    the /mnt/hgfs folder should b visible but it can’t can solve my problem ???

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