Symbolic file permissions unix

For example in crontap scripts. In bash, for a file test with -rw-rw-r-- root root , for rm test I receive the prompt rm: remove write-protected regular empty file 'test'?

The solution is to place sensitive files in directories for which users have read-only access. Community Bot 1. If you really need to change symlinks permission usually meaningless, as written in other answers , I was successful with using -R option of chown : chown -R myuser:mygroup link If -R was not used, the permissions were not changed.

Miroslav Mocek Miroslav Mocek That will work with GNU chown because -R implied -P there, however that's not guaranteed and won't work in some other chown implementations. The standard way to change the symlink ownership is with the -h option.

I've just updated the accepted answer which was incorrect. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses.

Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked 1. Related Hot Network Questions. Question feed. In this chapter, we will discuss in detail about file permission and access modes in Unix.

File ownership is an important component of Unix that provides a secure method for storing files. Here, the first column represents different access modes, i. The first three characters represent the permissions for the file's owner. For example, -rwxr-xr-- represents that the owner has read r , write w and execute x permission.

The second group of three characters consists of the permissions for the group to which the file belongs. For example, -rwxr-xr-- represents that the group has read r and execute x permission, but no write permission. The last group of three characters represents the permissions for everyone else. For example, -rwxr-xr-- represents that there is read r only permission. The permissions of a file are the first line of defense in the security of a Unix system. Directory access modes are listed and organized in the same manner as any other file.

Access to a directory means that the user can read the contents. The user can look at the filenames inside the directory. A user must have execute access to the bin directory in order to execute the ls or the cd command. To change the file or the directory permissions, you use the chmod change mode command. The first and probably easiest way is the relative or symbolic method, which lets you specify permissions with single letter abbreviations.

A chmod command using this method consists of at least three parts from the following lists:. For example, to add permission for everyone to read a file in the current directory named myfile , at the Unix prompt, enter:.

If you omit the access class, it's assumed to be all, so you could also enter the previous example as:. You can also specify multiple classes and types with a single command. For example, to remove read and write permission for group and other users leaving only yourself with read and write permission on a file named myfile , you would enter:. You can also specify that different permissions be added and removed in the same command.

For example, to remove write permission and add execute for all users on myfile , you would enter:. In each of these examples, the access types that aren't specified are unchanged. The previous command, for example, doesn't change any existing settings specifying whether users besides yourself may have read r access to myfile.

The chmod command also operates on directories. For example, to remove write permission for other users on a subdirectory named mydir , you would enter:. To change permissions recursively in all subdirectories below the specified directory, add the -R option; for example, to grant execution permissions for other users to a directory mydir and all the subdirectories it contains, you would enter:.

Be careful when setting the permissions of directories, particularly your home directory; you don't want to lock yourself out by removing your own access. Also, you must have execute permission on a directory to switch cd to it. The other way to use the chmod command is the absolute form, in which you specify a set of three numbers that together determine all the access classes and types. Rather than being able to change only particular attributes, you must specify the entire state of the file's permissions.

The three numbers are specified in the order: user or owner , group, and other. Each number is the sum of values that specify read, write, and execute access:. You can think of the three digit sequence as the sum of attributes you select from the following table:.