Some important commands regarding user and group
Tuesday, November 17, 2009
To Change owner of a file
chown user_name file_name
Example: You want to make gautam as owner of beragautam.tx
chown gautam beragautam.tx
To change owner and group of a file
chown user_name.group_name file_name
You can also use this command as follows –
chown user_nam:group_name file_name
(Please note, you can use either “:” or “.”)
If you want to assign a file would be used by a group use the following command.
chgrp special atanu.tx
Here group name is special and file name is beragautam.tx
What is a group?
A group is used to represent users, who have similar characteristics,exercise similar tasks and
enjoy similar permission and environment in a network. Now think about the situation here.
You have a group of users who need similar type of access to a file, beragautam.tx. What you will do? Very simple
Create a group.
Issue the command that enables the group to access the file
Give file access permission to this group. (Example, all permissions to owner and read and
execute permissions to group)
Make the users members of a group.
Do these tasks as defined below.
groupadd newgroup
chgrp newgroup bera.tx
chmod 750 beragautam.tx
And then add the user to this group.
vi /etc/group
At the bottom of the file verify the entry related to newgroup and add the user name. It
will look like –
newgroup:x:600:beragautam,gautam
Here, beragautam and gautam are members of the newly created group, ‘newgroup’. The thing
must be noted is, usernames are specified by comma (,) separated form. However,
instead of editing th e /etc/group file directly, we can use commands to add or remove
users from a group.
If we want to add members (in our example, the name of the group is acct and the
members are red and green), we can use the following command –
gpasswd –M red,green acct
If we want to add user ‘blue’ in the ‘acct’ group we can use the following command –
gpasswd –a blue acct
To remove user red from the acct group, we can use the following command –
gpasswd –d red acct
chown user_name file_name
Example: You want to make gautam as owner of beragautam.tx
chown gautam beragautam.tx
To change owner and group of a file
chown user_name.group_name file_name
You can also use this command as follows –
chown user_nam:group_name file_name
(Please note, you can use either “:” or “.”)
If you want to assign a file would be used by a group use the following command.
chgrp special atanu.tx
Here group name is special and file name is beragautam.tx
What is a group?
A group is used to represent users, who have similar characteristics,exercise similar tasks and
enjoy similar permission and environment in a network. Now think about the situation here.
You have a group of users who need similar type of access to a file, beragautam.tx. What you will do? Very simple
Create a group.
Issue the command that enables the group to access the file
Give file access permission to this group. (Example, all permissions to owner and read and
execute permissions to group)
Make the users members of a group.
Do these tasks as defined below.
groupadd newgroup
chgrp newgroup bera.tx
chmod 750 beragautam.tx
And then add the user to this group.
vi /etc/group
At the bottom of the file verify the entry related to newgroup and add the user name. It
will look like –
newgroup:x:600:beragautam,gautam
Here, beragautam and gautam are members of the newly created group, ‘newgroup’. The thing
must be noted is, usernames are specified by comma (,) separated form. However,
instead of editing th e /etc/group file directly, we can use commands to add or remove
users from a group.
If we want to add members (in our example, the name of the group is acct and the
members are red and green), we can use the following command –
gpasswd –M red,green acct
If we want to add user ‘blue’ in the ‘acct’ group we can use the following command –
gpasswd –a blue acct
To remove user red from the acct group, we can use the following command –
gpasswd –d red acct
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