Questions tagged [permissions]

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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36
votes
2answers
84k 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 ? ...
35
votes
3answers
21k views

How do I make a file NOT modifiable?

While logged in, I can do the following: mkdir foo touch foo/bar chmod 400 foo/bar chmod 500 foo Then I can open vim (not as root), edit bar, force a write with w!, and the file is modified. How ...
34
votes
13answers
14k views

Can I create a *super* super-user so that I can actually have a user that can deny permission to root?

I was thinking that it might be advantageous to have a user with permissions higher than the root user. You see, I would like to keep all of the activities and almost all existing root user ...
34
votes
7answers
41k views

Can root/superuser read my read-protected files?

On shared unix hosting, if I have a file sensitive-data.txt and I issue: chmod 600 sensitive-data.txt Can root user still read my file? Specifically I'm wondering if it's safe to store my password ...
34
votes
4answers
4k views

Why can't I execute shutdown when the permission is rwxr-xr-x?

I'm in /sbin and I see that shutdown has permissions rwxr-xr-x. Doesn't this mean that anyone can execute it?
33
votes
4answers
29k views

Wrongly set chmod / 777. Problems?

I was trying to run chmod -R 777 ./ but ended up typing chmod -R 777 / and set 777 on my entire machine. What can go wrong? How can I fix it?
33
votes
4answers
239k 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 ...
32
votes
5answers
2k views

One file wants to belong to two users. How? Hard linking fails

Two setuid programs, /usr/bin/bar and /usr/bin/baz, share a single configuration file foo. The configuration file's mode is 0640, for it holds sensitive information. The one program runs as bar:bar (...
32
votes
3answers
169k views

How to create a Samba share that is writable from Windows without 777 permissions?

I have a path on a Linux machine (Debian 8) which I want to share with Samba 4 to Windows computers (Win7 and 8 in a domain). In my smb.conf I did the following: [myshare] path = /path/to/share ...
32
votes
3answers
122k views

How do I find out if I am sudoer?

How does Linux system behave when I am not sudoer? Here is what happens if I try to use sudo: server:/tmp>$ sudo cal [sudo] password for user: Sorry, try again. Is it possible that I just don't ...
32
votes
4answers
67k views

Why cannot find read /run/user/1000/gvfs even though it is running as root?

Can someone tell me what I'm doing wrong, what this is, or how to fix it? I'm running Fedora 18 and getting the error shown [root@servername /]# find . -name ngirc find: `./run/user/1000/gvfs': ...
31
votes
11answers
201k views

VSFTPD, 553 Could not create file. - permissions?

I've set up VSFTPD on Amazon EC2 with the Amazon Linux AMI. I created a user and can now successfully connect via ftp. However, if I try to upload something I get the error message "553 Could not ...
31
votes
1answer
4k views

Why are executables in e.g. /usr/sbin writable by root?

Could you please explain why a binary compiled file (in, for example, /usr/sbin) has write permission for root user? For me, this is compiled. Meaning that direct write has no use and may expose file ...
31
votes
5answers
78k views

Setting multiple groups as directory owners

On my server I have directory /srv/svn. Is it possible to set this directory to have multiple group ownerships, for instance devFirmA, devFirmB and devFirmC? The point is, I want to subversion ...
30
votes
10answers
120k 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 -...
29
votes
5answers
58k views

-bash: /dev/null: Permission denied

I'm trying to create a new user on a Centos 6 system. First, I do useradd kevin Then, I tried to run commands as that user su - kevin However, I get the following error messages -bash: /dev/null:...
28
votes
5answers
11k views

How do file permissions work for the “root” user?

I have the following file: ---------- 1 Steve Steve 341 2017-12-21 01:51 myFile.txt I switched the user to root in the terminal, and I have noticed the following behaviors: I can read this file and ...
27
votes
6answers
27k views

Is there a web based converter between rwx and the octal version?

I can never remember what the conversion is from something like rw-r--r-- to 644. Is there a simple web based converter between the 2?
27
votes
3answers
93k views

How to restrict a user to one folder and not allow them to move out his folder

I have ubuntu server on digitalocean and I want to give someone a folder for their domain on my server, my problem is, I don't want that user to see my folders or files or to be able to move out their ...
27
votes
1answer
24k views

Execute a .exe on a samba share

I have a linux machine and a windows machine, the linux machine has a samba share with a .exe file on it. I can read and write files from the windows machine to the samba share, but I cannot execute ...
27
votes
2answers
66k views

How to remove ACL from a directory and back to usual access control?

We use a hosting server of FreeBSD 10.3, where we don't have the authority to be a superuser. We use the server to run apache2 for web pages of our company. The previous administrator of our web pages ...
26
votes
7answers
4k views

Why no permissions like Android or iOS?

When I install a program like GIMP or LibreOffice on Linux I'm never asked about permissions. By installing a program on Ubuntu, am I explicitly giving that program full permission to read/write ...
26
votes
4answers
70k views

using root to mkdir in another users home directory

having a bit of a difficult time trying to create a folder under another user's /home/devuser1/pubic_html folder. I'm trying to avoid using sudo and looking for an alternative. The permissions on the ...
26
votes
5answers
12k views

How to “jail” a process without being root?

Were I root, I could simply create a dummy user/group, set file permissions accordingly and execute the process as that user. However I am not, so is there any way to achieve this without being root?
26
votes
2answers
17k views

What does a dot after the file permission bits mean?

I performed an ls -la on directory on my CentOS 6.4 server here and the permissions for a given file came out as: -rwxr-xr-x. I understand what -rwxr-xr-x means, what I don't understand is the . ...
26
votes
2answers
4k views

Why can't root execute when executable bits are not set?

root user can write to a file even if its write permissions are not set. root user can read a file even if its read permissions are not set. root user can cd into a directory even if its execute ...
26
votes
1answer
9k views

User permissions inside and outside of LXC containers?

I'm running some services inside of Docker LXC containers on my server and I'm beginning to actually do serious things with them. One thing I'm not clear on is how user permissions work inside and ...
25
votes
1answer
6k views

Make group permissions same as user permissions

I want to set the group permissions for all files and subdirectories within a certain parent directory to whatever the user permission setting for that specific file or directory is. For example, ...
25
votes
6answers
14k views

How do I recursively check permissions in reverse?

There's a command, I think it comes with apache, or is somehow related to it, that checks permissions, all the way down. So if I have /home/foo/bar/baz it will tell me what the permissions are for baz,...
24
votes
7answers
80k views

“echo 3 > /proc/sys/vm/drop_caches” - Permission denied as root

I am currently having some issues with the cache. It is a little too much right now so I wanted to clear it. I googled and found this little command: sync && echo 3 > /proc/sys/vm/...
24
votes
4answers
25k views

Test effective permissions of file for user

Is it possible to test effective permissions of a file for a specific user? I normally do this by su user and then accessing the file, but I now want to test this on an user with no shell (i.e. a ...
24
votes
7answers
21k views

What to use to backup files, preserving ACLs?

When using the tar utility to store files in backups one loses the extended ACLs. Is there some commonly used and not hackish solution (like: create a script that will recrate the ACLs from scratch) ...
24
votes
1answer
29k views

Difference between owner/root and RUID/EUID

I am relatively new to the concepts mentioned in the question and reading about them from different sources only makes them more confusing. So this is what I understood so far: When we are given ...
24
votes
1answer
21k 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? ~...
23
votes
4answers
4k views

What is so special about Linux permission 004?

I was reading Practical Unix and Internet Security, when I came across the following lines which I couldn't comprehend. If you are using the wu archive server, you can configure it in such a way ...
23
votes
3answers
92k views

How do I set permissions recursively on a dir (with ACL enabled)?

For example, I want to give my colleagues write access to certain directory. Let's assume that subdirectories in it had access rights 775, files 664, and also there were some executable files in the ...
23
votes
3answers
17k views

Permissions/ownership of /usr/local/bin

From what I understand, the right place to put your own scripts is /usr/local/bin (for instance a script I use to back up some files). I notice that this folder is currently (by default) owned by root,...
23
votes
7answers
51k views

Why do I get “screen is terminating” without root?

I have installed screen on Fedora 19. When I test the command as root remotely through SSH, it works perfectly. For instance, if I enter screen a new terminal emulator is started and waits for ...
22
votes
2answers
68k views

Mount device with r/w access to specific user

How can I mount some device with read-write access for a given user?
22
votes
2answers
15k views

How do I remove a file with no permissions?

A hacker has dropped a file in my tmp dir that is causing issues. Nothing malicious except creating GB's of error_log entries because their script is failing. However, the file they are using to ...
22
votes
2answers
70k views

What is the difference between 'su -' and 'su root'? [duplicate]

Possible Duplicate: Why do we use su - and not just su? I understand that root doesn't have to be a superuser. But in the case that it is ... what is the difference between sudo su - and sudo su ...
21
votes
2answers
4k views

File permission with six bytes in git. What does it mean? [duplicate]

I performed a git commit command and it gave me the following reply: 7 files changed, 93 insertions(+), 15 deletions(-) mode change 100644 => 100755 assets/internal/fonts/icomoon.svg mode change ...
21
votes
4answers
2k views

Is there a reason why 'owner' permissions exist? Aren't group permissions enough?

I think I rather understand how file permissions work in linux. However, I don't really understand why they are split into three levels and not into two. I'd like the following issues answered: Is ...
21
votes
11answers
197k views

Transfer files using scp: permission denied

I try to transfer files from remote computer using ssh to my computer : scp My_file.txt user_id@server:/Home This should put My_file.txt in the home folder on my own computer, right? I get scp/...
21
votes
2answers
210k views

How to set the permission drwxr-xr-x to other folders?

I have few directores inside a folder like below - teckapp@machineA:/opt/keeper$ ls -ltrh total 8.0K drwxr-xr-x 10 teckapp cloudmgr 4.0K Feb 9 10:22 keeper-3.4.6 drwxr-xr-x 3 teckapp cloudmgr 4....
21
votes
1answer
1k views

Are SELinux rules enforced before or after standard linux permissions?

When SELinux is installed on a system are its rules enforced before or after the standard linux permissions? For example if a non-root linux user tries to write to a file with linux permission -rw-----...
21
votes
1answer
5k views

File owner must belong to file group?

I have a rather simplistic understanding of file permissions on *nix systems. I understand that there is a file owner and file group, but is there a hard and fast rule on whether the said file owner ...
21
votes
5answers
37k views

Forcing owner on created files and folders

I have a directory that contains data shared between a number of users. Access to this directory and anything underneath, will be controlled by the directory's group, which will be added to the users ...
20
votes
4answers
163k views

Which is more widely used: chmod 777 or chmod a+rwx [closed]

Out of the two options to change permissions: chmod 777 file.txt chmod a+rwx file.txt I am writing a document to send out to our customers, detailing that they need to change the file permissions of ...
20
votes
9answers
57k views

Vim Error E138: Can't write viminfo file $HOME/.viminfo!

I'm afraid I've run into something rather strange. When I open a file normally, vim README.txt, everything is fine. But upon sudo vim README.txt, the file renders blank, and gives me a E138: Can't ...