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.

Filter by
Sorted by
Tagged with
20
votes
4answers
2k views

What is a valid use case for an “execute only” file permission?

I was reading up on chmod and its octal modes. I saw that 1 is execute only. What is a valid use case for an execute only permission? To execute a file, one typically would want read and execute ...
20
votes
3answers
11k views

Can I make a public directory under a private directory?

I have a personal folder /a/b on the server with permission 700. I don't want others to list the contents in /a/b. The owner of /a is root. Now I need to open the full authorities of directory /a/b/c ...
20
votes
3answers
8k views

How to non-invasively test for write access to a file?

In a shell script, how do I easily and non-invasively test for write access to a file without actually attempting to modify the file? I could parse the output of stat, but that seems really complex, ...
20
votes
2answers
34k views

Find directories and files with permissions other than 775 / 664

I am moving a website from one server to another and Git does not store metadata such as file permissions. I need to find the directories and files that are not 775 / 664 respectively. Right now, I'm ...
20
votes
4answers
11k views

Precedence of user and group owner in file permissions

I just ran into something unexpected (for me) regarding file permissions on Linux (Arch Linux). Basically I have: userX in groupX fileX userX:groupX ---rwx---- What puzzles me: I cannot perform any ...
20
votes
5answers
2k views

Find files that a user can write, efficiently with minimal process creation

I am root. I would like to know whether a non-root user has write access to some files - thousands of them. How to do it efficiently while avoiding process creation?
20
votes
3answers
12k views

I accidentally chmod -R +x on a directory. How do I restore the correct permissions?

Well, to be specific, it was chmod -R 755. Now every file is executable, which I don't want. I am thinking that I should look at the first two bytes of each file for the #!, but will this cover ...
20
votes
3answers
29k views

Force the owner and group for the contents of a tar file?

I would like to create a tar file with contents belonging to an owner:group pair who do not exist on the system from which the file is being made. Here's the direction I've tried: tar ca --owner='...
19
votes
2answers
67k 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.
19
votes
3answers
165k views

How to change permissions from root user to all users?

I created a folder on the command line as the root user. Now I want to edit it and its contents in GUI mode. How do I change the permissions on it to allow me to do this?
19
votes
7answers
56k views

VERR_ACCESS_DENIED when trying to add a raw disk to virtual box

I created a virtualbox raw disk pointing to a functioning, booting USB drive with a small linux distro on it. sudo ./VBoxManage internalcommands createrawvmdk -filename ~/VirtualBox\ VMs/MyTinyLinux/...
19
votes
1answer
51k 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 ...
19
votes
2answers
1k views

What does chmod -u do?

By accident I ran chmod -u filename and it removed all of the permissions I had on filename. The man page does not reference a -u option. Experimenting I was able to conclude that it removes not all ...
18
votes
4answers
24k views

bash: /dev/stderr: Permission denied

After upgrading to a new release version, my bash scripts start spitting errors: bash: /dev/stderr: Permission denied in previous versions Bash would internally recognize those file names (which is ...
18
votes
1answer
11k views

GitKraken does not start anymore on Ubuntu 18.04

When I turned on my Ubuntu 18.04 yesterday and wanted to start GitKraken, it did not work. After I click its icon I see how the process tries to start in the upper left corner (next to "Activities") ...
18
votes
2answers
6k views

What are the different ways to set file permissions etc on gnu/linux

On Unix, a long time back, I learned about chmod: the traditional way to set permissions, on Unix (and to allow programs to gain privileges, using setuid, setgid). I have recently discovered some ...
18
votes
1answer
50k views

Difference between sudo user and root user [closed]

The /etc/sudoers file lists which users can do what with the sudo command The root user creates and modifies the /etc/sudoers file. This concept is difficult for me to understand. If all users ...
18
votes
1answer
26k 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, allowing ...
18
votes
1answer
1k views

If the suid bit has no effect on directories and the sticky bit has no effect on files, why aren't they combined into one bit?

Would this save one bit per file, or is there necessary padding that has to be used anyways? And even if there is padding, why not still combine them and utilize the extra bit for a new feature?
18
votes
2answers
68k views

Give user read/write access to only one directory

I'm running a server, and I need to give read/write access to a particular directory to a single user. I've tried the following: sudo adduser abcd sudo groupadd abcdefg chown -R .abcdefg /var/www/...
18
votes
1answer
11k views

gpg: WARNING: unsafe ownership on homedir '/home/user/.gnupg'

System: I am testing Linux Mint 19 Beta based on Ubuntu 18.04. I got this warning while installing an unrelated package: gpg: WARNING: unsafe ownership on homedir '/home/vlastimil/.gnupg' This is ...
17
votes
3answers
5k views

Purpose of permissions such as 0111 or 0333

What is the purpose of Linux permissions such as 111 or 333 (i.e. the user can execute, but cannot read the file), if the ability to execute does not automatically imply the ability to read?
17
votes
4answers
16k views

I added a user to a group, but group permissions on files still have no effect

I changed permissions of a file (chmod g+w testfile) and running ls -l testfile gives: -rwxrwxr-x 1 user1 user1 0 2011-01-24 20:36 testfile I then added a user to that group ("/etc/group" has user1:...
17
votes
3answers
12k views

What roles do DAC (file permissions), ACL and MAC (SELinux) play in Linux file security?

I need some clarification/confirmation/elaboration on the different roles DAC, ACL and MAC play in Linux file security. After some research from the documentation, this is my understanding of the ...
17
votes
1answer
3k views

ls -l vs ls -lL

I know this looks like a duplicate, but previously asked questions do not answer my question so in the shell I go to /home directory and create a directory there calling it play then I go to this ...
17
votes
4answers
10k views

set read and write permissions to folder and all its parent directories

I need to set read and write permissions for root user to directory subfolderN and all its parent folders till root. I can do it by hands: $ sudo chmod +rx /root/subfolder1/subfolder2/subfolderN $ ...
17
votes
1answer
9k views

Why can't sudo redirect stdout to /etc/file, but sudo 'nano' or 'cp' can? [duplicate]

Why does redirection, using sudo give me an error for the following commands? $ sudo printf "foo" >/etc/file bash: /etc/file: Permission denied $ sudo printf "foo" ~/file; cat ~file >/etc/...
17
votes
4answers
36k views

Permission denied to change gid(group) of a file I own

It appears I still miss some things about the way permissions work. I am on a debian 7 system btw. just now I have this file of which I downloaded and it belongs to myuser:myuser, that is both user ...
17
votes
2answers
54k views

How to add a ssh user who only has permissions to access specific folder?

How to add an ssh user who only has permissions to access specific folder? useradd -d /var/www/xyz.com.tr/musteri -s /bin/bash -g sshd musteri I created a user called musteri. I set its home folder ...
17
votes
2answers
10k views

Allow owner to create & read files, but not modify or delete

I would like to give a user permissions to create and read files in a particular directory, but not to modify or delete files. If the user can append to files that is ok, but I'd rather not. This is ...
17
votes
1answer
2k views

Tracing executable without read permissions

I found some surprising behavior on Ubuntu 14.04 when using strace on an executable, which I do not have read permission on. I wonder if this is a bug, or if some standard mandates this obscure ...
16
votes
8answers
27k views

Convert ls -l output format to chmod format

Say I have the following output from ls -l: drwxr-xr-x 2 root root 4096 Apr 7 17:21 foo How can I automatically convert this to the format used by chmod? For example: $ echo drwxr-xr-x | chmod-...
16
votes
5answers
5k views

How does the OS know that a command needs sudo?

When you run an executable, sometimes the OS will deny your permission to. For example running make install with the prefix being a system path will need sudo, while with the prefix being a non-...
16
votes
3answers
9k views

Why does chmod +w not give write permission to other(o)

When I run chmod +w filename it doesn't give write permission to other, it just gives write permission to user and group. After executing this command chmod +w testfile.txt running ls -l testfile....
16
votes
2answers
12k views

execute bit on directories, but not files [duplicate]

Possible Duplicate: How to apply recursively chmod directories without affecting files? What is the command to apply execute permission for directories (for traversal), but leave the execute bit ...
16
votes
4answers
20k views

Can I port user permissions across computers for an ext4 external hard drive?

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 ...
16
votes
5answers
34k views

How to revert chown command?

If I run: sudo chown -R user:user / Can I revert it to what it was before I ran it?
16
votes
2answers
10k views

How to set file permissions with touch command

It seems that whenever I create a file with touch the permissions are set to: -rw-r--r--. Is there some way that I can configure the permissions with touch or does this have to be done after with a ...
16
votes
5answers
20k views

chmod recursive permission on thousands of files

This is a more general question about 'chmoding' recursively. I have this script which at some point needs to change the permissions recursively in a folder which has a few hundred thousand files. ...
16
votes
3answers
15k views

Why doesn't umask change execute permissions on files? [duplicate]

If I change the umask to 0000, I'd expect a text file to be created with rwxrwxrwx permissions (based on my understanding of the umask, as described in the "possible duplicate" question) However, when ...
16
votes
3answers
14k views

How to modify write permission on current buffer in emacs?

Is it possible to change the write permissions on a file from inside emacs, without killing/re-opening the buffer? Sometimes I forget to modify the permissions on a file before opening it. I can ...
16
votes
2answers
4k views

Cannot expand asterisk without proper permission

Can someone explain to me the following? $ ls -ld /temp/sit/build/ dr-xr-s--- 3 asdf qwer 4096 Jan 31 2012 /temp/sit/build/ $ ls -ld /temp/sit/build/* ls: /temp/sit/build/*: Permission denied So ...
16
votes
2answers
23k views

addgroup vs groupadd

I happen to know there is a slight difference between adduser and useradd. (i.e., adduser has additional features to useradd, such as creating a home directory.) Then what is the relation between ...
16
votes
9answers
70k 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/...
16
votes
1answer
38k 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, ...
16
votes
2answers
19k views

Hard-link creation - Permissions?

Which permissions affect hard-link creation? Does file ownership itself matters? Suppose user alice wants to create a hard-link to the file target.txt in a directory target-dir. Which permissions ...
16
votes
3answers
30k views

How to grant non-root user access to device files

I have device file that appears in /dev when a specific board is plugged in. The read and write operations to it work just fine, but in order to open the device file the program needs to be executed ...
16
votes
2answers
20k views

what is 'nogroup' group's purpose

When I list al groups I see one called 'nogroup'. What is this for? Is it supposed to be least privileged one or something? I'm using ubuntu 11.04.
16
votes
2answers
14k views

What relationships tie ACL mask and standard group permission on a file?

At first I create a file and check it's standard permissions and ACL entries: $ touch file; ls -l file; getfacl file -rw-r--r-- 1 user user 0 Jul 30 16:26 file # file: file # owner: user # group: ...
16
votes
2answers
5k views

rsync: skip files for which I don't have permissions

I'm using rsync -rlptD to copy a directory from another user. There are a few files (I have no way of knowing these in advance) which I don't have permission to copy. Is there a way have rsync ignore ...