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.

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ISO file readonly?

I have an ISO file and I mount it under /mnt/isofile. Then I copied this file to another folder. But the contents are read-only and belonged to root. I tried to use chmod and chown. But it prompts ...
7
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2answers
12k views

What is nobody user and group?

On my server (Synology DS212) some files and folders have nobody nobody users and groups. What are the characteristics of this user and group? Who can write of read this file? How can I change it ? ...
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2answers
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Permissions: What's the right way to give Apache more user permissions?

Context: I am making an in-browser control panel that gives me one button access to a library of scripts (.sh and .php) that I've written to process various kinds of data for a project. It's a "one ...
4
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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
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2answers
241 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 ...
29
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4answers
9k views

How to recover from a chmod -R 000 /bin?

And now I am unable to chmod it back.. or use any of my other system programs. Luckily this is on a VM I've been toying with, but is there any way to resolve this? The system is Ubuntu Server 12.10. ...
35
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3answers
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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 ...
21
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2answers
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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 ...
35
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7answers
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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 ...
19
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7answers
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“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
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1answer
21k 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, ...
45
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2answers
4k views

Why is rm allowed to delete a file under ownership of a different user?

From the post Why can rm remove read-only files? I understand that rm just needs write permission on directory to remove the file. But I find it hard to digest the behaviour where we can easily delete ...
14
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3answers
55k 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 ...
21
votes
1answer
33k 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 ...
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
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8answers
47k 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 /usr/lib/jvm/java-6-openjdk/jre/bin/...
11
votes
4answers
9k 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
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5answers
20k 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 /usr/...
10
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1answer
17k 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 ...
9
votes
1answer
4k views

how to view a directory's permission

What is the command with which you can directly view the permission bits of a directory?
8
votes
1answer
5k 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
11k 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 ...
6
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2answers
430 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 ...
3
votes
1answer
5k 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
2answers
814 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
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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 ...
12
votes
1answer
9k 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
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4answers
24k views

'chmod g+s' command

Hello I want to understand the role of the chmod g+s command in Unix. I also would like to know what it does in this particular context: cd /home/canard; touch un; chgrp canard .; chmod g+s .; touch ...
8
votes
2answers
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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
12k 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
8k 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 debianbox@...
5
votes
3answers
531 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
1answer
1k views

Allow certain guests to execute certain commands

I would like to create a new user on some of my Debian/Ubuntu hosts that is able to update the server using the commands apt-get update and apt-get dist-upgrade, but I do not wan't to give them full ...
4
votes
5answers
2k views

Protect folder from sudoers

Is there an ability to not allow sudoers view your folder (only you and root can access folder)?
3
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2answers
444 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 ...
3
votes
3answers
187 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
3answers
5k views

How to prevent users from deleting a directory?

I tried "chattr +i DIRNAME", it's great, but I cannot create files in the DIR after chattr. What else are there to prevent users from deleting a Directory? root@HOST ~] mkdir test [root@HOST ~] ...
3
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2answers
148 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?
2
votes
1answer
188 views

View temporary files which exist for milliseconds

I'm trying to debug a program which is not logging the information I need. Fortunately, it does write temporary files which should contain the information. These files are written to a directory like: ...
2
votes
4answers
648 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 ...
1
vote
1answer
1k views

Create files that both www-data and myuser can edit

I have a directory to store invoices - drwxrwxr-x 2 me www-data 49152 Sep 9 13:38 invoices There are two applications that write files to this dir. PHP web application -rw-r--r-- 1 ...
0
votes
2answers
647 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 ...
9
votes
2answers
4k views

recursively change file permission but not directories?

I was doing a mass recursive change of permissions of some files that I had migrated to a unix system. I changed them to ug+rw, but then I found that I could not traverse subdirectories. I looked at ...
7
votes
3answers
22k 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 ...
7
votes
2answers
3k views

How to set permissions in /sys/ permanent?

I'm starting X as a user and need to set my keyboard brightness in /sys/class/leds/asus\:\:kbd_backlight/brightness. The /sys/ directory gets recreated after reboot, so the permissions will reset too. ...
5
votes
2answers
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What are the runtime permissions of a cron job?

When a cron job runs with what privilege does it execute? I'm not sure about that. Is it with the same privileges of the user that added it via crontab -e?
4
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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
2answers
2k 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
2answers
214 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 ...