Permissions are the unix way of controlling access to resources such as files, directories and devices and may be specified for an owner, group, or all users.

learn more… | top users | synonyms (1)

4
votes
3answers
2k views

What mechanism prevents any user from accessing any other user's files via root?

On a multi-user system, what protects against any user accessing any other users files via root? As context, the question is based on my understanding as follows: There are two commands related to ...
4
votes
1answer
1k views

Write-only permission for a directory doesn't allow to rename (move) files inside?

In fact, I would like to ask more general question -- "what does write permission for a directory allow you to do exactly?" -- but let's approach it with a concrete example. It is a long question, if ...
1
vote
2answers
163 views

Broken system after chmod -R 644 /

I use debian jessie and I have done one of those bad mistakes and broke my system with a mistyped command and worse mistakes that follow in such situations. Trying to fix some permissions I ...
127
votes
9answers
16k views

How to chmod without /usr/bin/chmod?

Today I was told a tale by a Unix trainer, a tale where the root password got leaked to the students, and one of the fellas removed the execute permission from /usr/bin/chmod itself. How do you ...
35
votes
3answers
2k views

How does vim steal root owned files?

Witness the following: sh-3.2$ mkdir testcase sh-3.2$ cd testcase sh-3.2$ sudo touch temp sh-3.2$ ls -al total 0 drwxr-xr-x 3 glen staff 102 19 Dec 12:38 . drwxr-xr-x 12 glen staff 408 19 Dec ...
17
votes
2answers
18k views

What does the 'd' mean in ls -al results and what is that slot called? [duplicate]

In Linux, what does the d mean in the first position of drwxr-xr-x? And what are all of the possible letters that could be there, and what do they mean? I'm trying to learn more about the Linux file ...
18
votes
7answers
51k views

“Symbolic link not allowed or link target not accessible” / Apache on CentOS 6

I've got a brand new CentOS 6 installation, which has a symlink in the document root to my development files: [root@localhost html]# ls -l total 4 -rwxrwxrwx. 1 root root 0 Sep 18 20:16 index.html ...
11
votes
1answer
19k views

How to (safely) move /tmp to a different volume?

Today the /tmp directory filled up on a machine at work. The problem was, it was on the root partition which wasn't very big. In order to fix this, a co-worker created a /new/tmp directory elsewhere, ...
7
votes
1answer
1k views

Give a specific user permissions to a device without giving access to other users

I have a card reader attached on /dev/sdb. What I do is giving all permissions to owner, group and the rest of the world, using: sudo chmod 777 /dev/sdb Can I just use another combination, ...
34
votes
6answers
17k views

Can a script be executable but not readable?

Is it possible to execute a script if there is no permission to read it? In root mode, I made a script and I want the other user to execute this script but not read it. I did chmod to forbid read and ...
13
votes
1answer
1k views

Can I restrict a user to use special programs?

Is it possible to add a user and restrict him to run special programs? For example after this user logs in, he can only open Firefox to use Internet and no other programs can be run by this user. For ...
15
votes
8answers
42k views

Problem to launch java at Debian: “error while loading shared libraries: libjli.so”

I'm trying to launch java: $ java -version java: error while loading shared libraries: libjli.so: cannot open shared object file: No such file or directory $ ldd ...
10
votes
3answers
8k views

External hard drive permissions - ext4

I have an external USB 3 disk drive (2TB capacity) that is most likely going to be moved from machine to machine. The disk has a GUID partition table and an ext4 partition. I am unable to write to the ...
9
votes
3answers
38k views

granting write permissions to a group to a folder

How can I grant write permission to 1 group ? I have 2 users (alex and ben). alex is member of group alex and of group consult. ben is member of group ben and of group consult. I want to grant read ...
9
votes
5answers
18k views

How to get back sudo on Ubuntu?

I have done this: sudo chown -R myname /usr/ and now I can't use the sudo command because of this error: sudo: must be setuid root And as I read this means that the owner of this file ...
10
votes
1answer
14k views

Group within group file permissions

I tried finding this on here, but couldn't so sorry if it's a duplicate. Say I have 2 groups and a user: group1, group2, user1 with the following structure: group1 is a member of group 2, user1 is a ...
8
votes
1answer
4k views

Symbolic link permissions

I have access to a remote Linux machine where everytime I create a symbolic link, it is created by default with the following permissions: lrwxrwxrwx If I try to change the permissions of the ...
6
votes
2answers
310 views

Folder with ONLY write permission is useless… right?

Having worked with Linux for years, and finding myself with some free time, I decided to revisit some basics. So I re-read the stuff about permissions (without checking source code), and its special ...
6
votes
2answers
10k views

Using setfacl to allow group members to write to any file in a directory

I'd like to use setfacl so that anyone in group 'app' can edit any file contained within /usr/local/users/app regardless of what the traditional UNIX permissions say. I have two users john and ben. I ...
5
votes
2answers
20k views

Mount device with r/w access to specific user

How can I mount some device with read-write access to specific user?
2
votes
2answers
763 views

Is a -rw-rw-rw- file really inaccessible inside a drwxrwx— directory?

Say I have a directory with these permissions: drwxrwx--- Inside this directory, a file with these permissions: -rw-rw-rw- Is the file readable/writable by everyone or not ? If not, how secure ...
2
votes
1answer
4k views

How to mount USB stick on Debian Sid?

I've just installed Debian Sid on my computer but I cannot mount external USB drives as you can see in the image. Mounting failed Cannot mount "SENZATITOLO" Not authorized What should I ...
2
votes
1answer
1k views

How do I restore default owner of files in /var/ directory? [duplicate]

Accidentally in /var/ directory I ran chown root . -R;chgrp root . -R. Now services like mysql don't start. Is there a way to restore default owner and groups? If there is no way, what is the default ...
16
votes
1answer
26k views

Unable to delete file, even when running as root

I am in the process of migrating a machine from RHEL 4 to 5. Rather than actually do an upgrade we have created a new VM (both machines are in a cloud) and I am in the process of copying across data ...
12
votes
1answer
8k views

Why does root get Permission denied when accessing FUSE directory?

I use a FUSE filesystem with no problems as my own user, but root can't access my FUSE mounts. Instead, any command gives Permission denied. How can I give root the permission to read these mounts? ...
8
votes
2answers
3k views

Evince fails to start because it cannot read .Xauthority

I'm logged in remotely over SSH with X forwarding to a machine running Ubuntu 10.04 (lucid). Most X11 applications (e.g. xterm, gnome-terminal) work fine. But Evince does not start. It seems unable to ...
7
votes
1answer
10k views

I can't remove a directory tree with rm -rf

This seems very strange to me. I'm running kernel 2.6.37.2 and ran: ~]$ cp -r /proc/ here ~]$ rm -rf here I get some permission denies when copying as expected and I eventually hit Control-C. I get ...
5
votes
3answers
6k views

Write access without read access

Is it possible for a user to have a write access to a file and not be able to read it? How is it possible? I tried the following commands: debianbox@debian:~/posix/io$ touch filetest ...
5
votes
3answers
519 views

Unix users, groups, and permissions

I don't understand unix users, groups, permissions, etc. For example, things managed by the chmod, chgrp, usermod, groupadd, etc. commands. How do all these things work?
4
votes
3answers
2k views

Permissions issues for shared directory on a server

The setup is we have a VPS running Debian Squeeze, and I've set up a shared directory for us to share files. So far I've followed this guide: ...
3
votes
2answers
2k views

Why can't I delete this file as root?

I have directory exam with 2 files in it. I need to delete files but permission is denied. Even rm -rf command can't delete these files. I logged in as a root user.
3
votes
3answers
135 views

Can a file be edited with the 'write' permission on it but not on its parent directory?

Suppose the owner/user doesn't have the write permission on a directory but he has it on a file under it. Can the file here be edited or not? If yes, is there any situation where the file cannot be ...
3
votes
2answers
124 views

Permissions to change only directory content and not itself

We have a directory and want to protect that from remove and rename, but we need to be able to rename, remove and create contents. What we can do?
3
votes
2answers
425 views

Permissions of webserver's root directory

I've had this issue on several setups, and I'm unsure of how to handle it. At first, all of /var is owned by root:root. Clearly I don't want the web directory to be owned by root, so I do chown ...
2
votes
4answers
559 views

USB 500GB external drive mounted with undetermined permissions, missing data

Note: This situation is evolving. Please see the output at the end of this question for the current situation. I'm using Linux Mint 14. Recently, I repartitioned one of my hard drives, and I backed ...
0
votes
2answers
536 views

setfacl access issues

I have a list of users (user1,user2,user3,superuser). user1, user2 and user3 belong to a usergroup called normalusers . Now, I need to issue the access control list command for the user superuser to ...
7
votes
3answers
17k views

How to check which Apache group I can use for the web server to write?

I'm trying to make Wordpress work. I currently have this error message: Could not create directory. /var/www/html/wp-content/upgrade/theme_name when trying to upload a theme. This is the ...
4
votes
2answers
1k views

How does the 'passwd' command gain root user permissions?

How does Linux know that it has to give euid 0 (uid of root) to only certain process like passwd, setuid, etc. If a process can gain root permissions, will it not lead to potential security breaches ...
3
votes
1answer
2k views

Can't rename a directory that I own

I have a directory with a big load of sub directories. I own all of them, and the permissions are all 777. pascal@azazel /box $ ls -al total 147872 drwxr-xr-x 293 root root 12288 aoû 22 19:44 ...
2
votes
3answers
58 views

Change files with Editor that need sudo permissions

I want to change files with KomodoEdit, that need sudo permissions. I cant start KomodoEdit with sudo tho (for whatever reason). Can I somehow grant Komodo permission to edit those files (in ...
2
votes
2answers
117 views

How to change permission of anonymous pipe?

I've the script which loads the SSH key from the variable (as part of script in CI environment) in order to not keep the private file in the public repository, however ssh-add complains about the ...
2
votes
2answers
67 views

Who should own files shared by a group and where should they go

I am configuring a Linux work station that will be used by a small number of users (20-30). These users will belong to a small set of groups (5-10) with each user belonging to at least one group and ...
2
votes
2answers
1k views

How to hide someone else's directories from a user?

I have several folders: /home/user1/ -u user1 -G user1 /home/user2/ -u user2 -G user2 /home/user3/ -u user3 -G user3 I created three users user1, user2, user3. Each user has their own group. Any ...
2
votes
4answers
471 views

Strange file ownership with Ubuntu

Normally we know when we create one file in Linux, the file's owner and group will set with the creator. For example, I have one user, usera, after I execute usera@srv1:$touch 1.txt I will find the ...
2
votes
2answers
3k views

can't change file permission

Whenever I create or copy few shell files to usb storage device, then I am not able to make them executable. If I create test.sh, it's default file permission will be 644, but when I execute ...
2
votes
2answers
838 views

Mount permissions always blocked

How do I authorise my non-root user to manually mount/unmount ALL media on my desktop. I always get denied permission. Media refers to all mountable USB devices and other partitions on my HDD as ...
2
votes
1answer
740 views

pure-ftpd permission denied on external usb drive

I have a sheevaplug PC (Debian installed) that I'm trying to setup my personal FTP server with. So far I was able to set up auto mounting and installed pure-ftpd. I currently have autofs setup to ...
1
vote
2answers
2k views

newgrp and groups assigned via pam_group.so

For convenience reasons I tend to assign special group memberships like floppy, audio, plugdev, video etc. via /etc/security/group.conf (pam_group.so) mechanism instead of adding all users to this ...
0
votes
0answers
266 views

DD-WRT: /tmp exec permission

After making a simple hello world OpenWrt package I installed it to the /tmp folder on the dd-wrt device. The program shows up in ls /tmp but when I try to execute it, it shows me /tmp/helloworld: ...
0
votes
2answers
271 views

File permissions of file when tranferring from Windows to Unix

When I am uploading a file from windows PC to Unix ,the permissions of file are --wxr----t on unix machine , whereas umask is 0022 .I am not able to understand from where is the file getting ...