How To Change Directory Permissions In Linux
This information is intended to assist GLADE file system users empathize common POSIX-standard commands. Note that:
- Experienced users may adopt to manage permissions using octal numbers rather than the methods described below.
- Some also find access control lists (ACLs) useful for facilitating curt-term file sharing amongst selected users. SeeUsing access control lists.
Existing files and directories
Should yous demand to modify permissions for existing files or directories – to permit other users to alter or execute them, for example –follow the chmod examples beneath.
New files and directories
Files and directories that you create in your GLADE file spaces have sure permissions by default. To change the default settings,utilise the umask command described below.
Folio contents
- Near permissions
- Changing permissions with chmod
- Examples
- Changing default permissions with umask
- Instance
- Managing groups
- Identifying current group and others - id
- Changing current group - sg
- Changing default group
- Changing group buying of a file or directory - chgrp
About permissions
Files in a UNIX arrangement accept associated permissions that determine who can read (r), write (westward), and execute (10) them.
Directory permissions use those same flags to indicate who can list files in a directory (r), create and remove files in the directory (w), or cd into or traverse (10) the directory. Carefully consider both the file permissions and the directory permissions to get the desired terminate result. For example, you lot tin can give a user read permission for a file, but the user won't have access to it without besides having permission to traverse the directory tree that contains the file.
Three boosted things to note regarding directory permissions:
- Users who have write permission for a directory can delete files in the directory without having write permission for those files.
- Subdirectories can take less restrictive permissions than their parent directories. However, if you modify directory permissions recursively (seechmodbelow), y'all are changing them for all of the files and subdirectories in that directory tree.
- An alternative to changing permissions recursively is to gear up them selectively as shown inthis example
About execute flags: X vs. x
When setting permissions, the execute flag can be set to upper-case X, which differs from the lower-case ten setting. The 10 permission allows execution just if the target is a directory or if the execute permission has already been set for the user or group. Information technology is useful in the case of handling directory trees recursively.
To meet who can piece of work with your files and directories, log in and look at the output of an ls ‑l command.
Hither is an instance.
The outset column is a cord of 10 permission flags.
The showtime flag indicates, for nigh directory contents, that what is listed is a file (-) or a directory (d).
The other 9 flags, in groups of iii, indicate:
| - the user's (owner's) permissions | -rwxr-xr-x |
| - group members' permissions | -rwxr-xr-x |
| - others' permissions | -rwxr-xr-x |
"Others" means everyone else who can log in on the machine.
Irresolute permissions with chmod
To modify the permission flags on existing files and directories, employ the chmod control ("change way"). Information technology can be used for individual files or it can exist run recursively with the -R option to change permissions for all of the subdirectories and files within a directory.
The chmod command specifies which class or classes (user, group, other) accept access to the file or directory in various modes (read, write, execute).
- Utilize the operators + and - to add or remove selected permissions for a form without irresolute its other permissions.
- Use = to specify all of the permissions for a form at once. If a grade is not mentioned explicitly, the permissions are unchanged even if the = operator is used for a different grade.
Follow this format:
chmod [classes][operator][modes] filename
Examples
Add together selected permissions for a grouping
Only the owner tin read, write, and execute this file:
-rwx------ i username group 57 April 11 12:29 filename
Add group (yard) permissions to read (r) and execute (x) like this:
The new file permissions are shown hither:
-rwxr-ten--- ane username grouping 57 May fourteen 09:54 filename
Note that the permissions that were non specified were not changed: The user grade permissions and other class permissions did not alter, and the writing permission for the grouping class remains unchanged.
Specify all permissions for a group
To set permissions for a single class, such every bit group (g), apply the = operator.
In this example, the only permissions affected were those for the specified class: grouping. The group can only read or execute the file, but not write. Permissions for the user class and other class were not inverse because they were non specified.
Specify permissions for sets of classes
To set permissions for multiple classes with a single control, divide the class settings with a comma.
chmod u=rwx,1000=rwx,o+rx filename
The new file permissions are shown hither:
-rwxrwxr-x 1 username group 57 May 14 09:54 filename
Prepare permissions selectively
This case shows how to give your group access to all of the files and subdirectories in a directory just limit other users' access to specified files.
chmod -R u=rwx,grand=rwx,o+ten /glade/u/home/username/directory/ chmod u=rwx,g=rwx,o+rx /glade/u/habitation/username/directory/subdirectory/file1 chmod u=rwx,one thousand=rwx,o+rx /glade/u/home/username/directory/subdirectory/file2
The outcome is that grouping members have all rights to files in the specified directories and subdirectories. Others have permission to traverse the directories as needed to read and execute two specified files.
Changing default permissions with umask
To change the default permissions that are set when you create a file or directory within a session or with a script, apply the umask command.
The syntax is similar to that of chmod (above), merely use the = operator to set the default permissions.
Example
The umask examples shown hither will requite you and group members read, write, and execute permission. Others will take only read and execute permission.
bash users
tcsh users
Managing groups
Several boosted commands are useful for managing groups to control who tin admission files and directories. For case, you can limit access to users who share your cadre-hour or storage space allocation.
Say you don't want all members of the ncar group to accept grouping permissions to read, write, and execute sure files. Yous should have a UNIX grouping that corresponds to your project code – such every bit group uabc0001 for project code UABC0001. Y'all can use the commands described below to set or change group buying of sure files and directories then just members of that UNIX group have permission to admission them.
If in that location is no group that allows you to share as needed with other users who accept NCAR user accounts:
- Consider using thesetfacl commandto set upwardly an admission control list.
- Asking creation of a custom group.
To share with colleagues who do non take NCAR user accounts, consider using theNCAR Data Sharing Service.
Identifying current group and others - id
Files or directories that you create or edit become associated with your electric current UNIX group. Usually, that is your default primary group unless you lot change groups later you log in. (See "Changing electric current group" beneath.)
If you lot aren't certain what your electric current group is, or which other groups you lot belong to, you lot can find out by running the id command after you log in. It will return your user ID (uid) and your current group (gid), and information technology will list any other groups with which yous are associated.
Case:
id uid=12345(jsmith) gid=g(ncar) groups=chiliad(ncar),54321(cisl)
Changing current group - sg
To alter from one grouping to another during a login session, follow this example using the sg command and the proper name of the new group.
The command will start a new shell with your new current group ID in effect. When you exit that shell, you change dorsum to your previously used grouping ID.
Some users adopt newgrp over sg for this, merely sg has the reward of retaining your existing user environment while changing your current grouping.
Changing default group
To alter your default chief group – the group that volition exist in effect each fourth dimension you subsequently log in – use the Systems Bookkeeping Manager . Changes fabricated in SAM typically accept upshot the next business organization mean solar day.
Changing group ownership of a file or directory - chgrp
Apply chgrp as shown here to change ownership of a file or directory to a different grouping.
chgrp new_groupname filename chgrp new_groupname directory
To modify group ownership of a directory and all of the files and subdirectories in that directory, use chgrp recursively.
chgrp -R new_group directory
Source: https://arc.ucar.edu/knowledge_base/68878469
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