set the file right

[juno2]

I have create a file on the system , how to set the file can only update/delete by the owner , the other users can read only ? thx

[S.K. Chan · Accepted solution]

Two things to consider, the ownership of the file and its permission. Make sure the file is first owned by the user.
# chown skchan:users file
==> Change ownership of "file" to owner=skchan group=users
# chmod 644 file
==> That gives skchan (the owner) read and write permission. Other users in group "users" can only read and the rest of the world can only read.
In both cases man chmod and man chown wil give you the details.

[juno2]

Thx ,

As I know , add the permission "t" can also prevent the user to delete the file , how to set it ?

[Michael Tully]

After the file has been created.

$ chmod 600 myfile

Before creation of the file set your umask

$ umask 077
$ touch mynewfile

Regards
Michael
"When I have trouble spelling, it's called fat finger syndrome"

[S.K. Chan]

I suppose I need to add one more comment. The ownership and permission of the directory where this file is located is also crucial. In order for file to be protected from deletion the dir permission should not allow a "write". A simply example is the /tmp dir which has a 777 (drwxrwxrwx) permission. Placing the above "file" in /tmp will allow anyone to delete it even though the permission of "file" is protected.

[juno2]

how to set the file only the owner can delete/update , other users can only read ? thx

[Michael Tully]

The -t is called sticky bit. This is set so that people only delete their own files from within shared directories like /tmp
To set the permission of the directory/filesystem:

$ chmod +t /tmp

Regards
Michael
"When I have trouble spelling, it's called fat finger syndrome"

[T G Manikandan]

sticky bit "t" can only be set to the directories.

It means that only the owner or the super user can delete the file in the dir.

#chown 1777


THanks

[juno2]

Thx Michael,

I try r method "chmod +t /tmp/file" , then the file premission changed to "-r--r--r-T" , however , i tried other users can still delete/update it ,even change the ownership after update the file. thx

[juno2]

thx T G Manikandan ,
if it is file not dir , how to make this setting ? thx.

[T G Manikandan]

If that is required for files then you need to turn on ACL's.

Using ACL's you can do that.

check the man pages of setacl

[T G Manikandan]

check the man pages of acl.

[juno2]

thx all,
except ACL , is there any other method can do that ?thx

[T G Manikandan]

how to set the file only the owner can delete/update , other users can only read.

If this is only what you want you can just do what Chan has replied.

Do a chmod 644 on the file so that only owner can update/delete others can only read?
What else you are looking for?

[Jean-Louis Phelix]

hi,

You've got all needed answers ... But I can summarize :

- Owner can update and others can only read :

chmod 644 file

- Owner can delete file but others can't, this is managed at the directory level (the directory where the file is located) :

. If directory belongs to the owner of the file :

chmod 755 dir

. If directory is a public one (like /tmp) :

chmod 1777 /tmp

Regards.