TL;DR
To use chmod 755 in Linux, you can try these methods:
- Use Numeric Representation: Set permissions to 755 using
chmod 755 file_name
to allow read, write, and execute access for the owner and read and execute access for the group and others. - Use Symbolic Representation: Set permissions using
chmod u=rwx,g=rx,o=rx file_name
to grant read, write, and execute access to the owner, read and execute access to the group, and read and execute access to others. - Combine Numeric and Symbolic Representation: Fine-tune permissions by executing
chmod 7+rwx,5+rx,5+rx file_name
to set permissions to 755 while adjusting specific access levels for the owner, group, and others.
Read the article below to learn more about using chmod 755 in Linux, important security considerations, and some common mistakes to avoid.
Ever wondered how to control who can access, modify, or run your files in Linux? Well, I’ve got you covered! In this post, I’ll walk you through chmod
755, a handy command that lets you manage file permissions easily.
You’ll learn simple ways to set permissions using numbers and letters, ensuring your files stay safe and accessible. Plus, I’ll share important tips to keep your Linux system secure. Whether you’re new to this or looking to sharpen your skills, this guide will help you navigate file permissions like a pro.
What is chmod
?
chmod
is a command in Linux used to change the permissions of files and directories. Permissions control who can read, write, or execute a file. By using chmod
, you can set these permissions to ensure proper access and security.
The basic syntax of the chmod
command is:
chmod [permissions] [file or directory]
For example, to change the permissions of a file named example.txt
to 755
, you would use:
chmod 755 example.txt
Different Ways to Change Permissions Using chmod
You can change permissions in two ways with chmod
: symbolic and numeric.
- Symbolic Method: Uses letters to represent permissions.
r
for readw
for writex
for execute
Example:
chmod u+rwx,g+rx,o+rx example.txt
This gives the owner (u
) read, write, and execute permissions, the group (g
) read and execute permissions, and others (o
) read and execute permissions.
- Numeric Method: Uses numbers to represent permissions.
4
for read2
for write1
for execute
Example:
chmod 755 example.txt
This sets the permissions to read, write, and execute for the owner, and read and execute for the group and others.
Breaking Down chmod 755
When you set permissions to 755
, you are defining what the owner, group, and others can do with a file or directory.
- Owner Permissions: The owner of the file or directory can read, write, and execute it.
- The first
7
in755
means the owner has all permissions (read, write, and execute). 7
is the sum of4
(read) +2
(write) +1
(execute).
- The first
- Group Permissions: The group members can read and execute the file or directory but cannot write to it.
- The second
5
in755
means the group has read and execute permissions. 5
is the sum of4
(read) +1
(execute).
- The second
- Others Permissions: All other users can read and execute the file or directory but cannot write to it.
- The last
5
in755
means others have read and execute permissions. 5
is the sum of4
(read) +1
(execute).
- The last
By setting a file or directory to 755
, you ensure that the owner can fully interact with it, while group members and others can only read and execute it. This is useful for sharing files securely while keeping control over modifications.
How to Use chmod 755 in Linux
To use chmod 755
in Linux, you have three methods to set permissions. First, using numeric representation involves assigning a three-digit number where each digit defines permissions for owner, group, and others (e.g., chmod 755 file_name
).
Second, symbolic representation uses letters (u
, g
, o
) to specify permissions (r
, w
, x
) for each category (chmod u=rwx,g=rx,o=rx file_name
). Third, combining both methods lets you tailor permissions precisely, ensuring secure file access and execution while limiting write capabilities as needed.
Now, let’s understand the three different methods to set file permissions using chmod 755 in Linux here:
1. Use Numeric Representation
Numeric representation allows you to set permissions using a three-digit number. Each digit corresponds to a specific user category: owner, group, and others. Here’s how you can use chmod 755 in Linux using numeric representation:
- Identify the file or directory for which you want to set permissions. Or you can create a sample file to test-run the
chmod 755
command.

- Here’s the breakdown of the numeric representation to understand:
- The 7 indicates read, write, and execute permissions for the owner.
- The 5 signifies read and execute permissions for the group.
- The final 5 represents read and execute permissions for others.
- Now, determine the appropriate numeric representation for your use case, considering the desired permissions for each user category – which, in this case, is:
chmod 755 file_name
- Execute the
chmod 755
command in the Terminal window while replacingfile_name
with the actual file or directory name:

- Verify the changes by listing the file permissions using the
ls -l
command.

2. Use Symbolic Representation
Symbolic representation provides a more intuitive way of setting permissions using letters that represent users and their corresponding permissions. Let’s go through the steps:
- First, look for the file or directory you want to set permissions for.

- Explanation of symbolic notation:
- The
u
stands for the owner of the file. - The
g
represents the group the file belongs to. - The
o
denotes others or everyone else.
- The
- Decide which permissions you want to grant or deny for each category (e.g., read, write, or execute). In this case, you can use:
chmod u=rwx,g=rx,o=rx file_name
- Execute the chmod 755 command in the Linux command prompt, replacing
file_name
with the actual file or directory name.

- Verify the changes by listing the file permissions using the
ls -l
command.

3. Combine Numeric and Symbolic Representation
In some cases, it may be beneficial to combine both numeric and symbolic representations. This allows you to fine-tune permissions based on specific requirements. Here’s how you can do it:
- Identify the file or directory for which you want to set permissions. You can use
cd
to navigate to the desired directory and then executels
to view files for using thechmod 755
command.

- With with the
ls -l
command, determine the permissions you wish to grant for each user category to use both numeric and symbolic representations.

- Then, execute the following command in your Terminal, replacing
file_name
with the actual file or directory name and adjusting the permissions accordingly:
chmod 755 file_name && chmod +rw file_name
- Once the commands are executed, verify the changes by listing the file permissions using the
ls -l
command in that particular directory.

8 Security Considerations When Using chmod 755 in Linux
While chmod 755 provides a balance between functionality and security, it’s important to consider the following security considerations when utilizing it in a Linux environment:
- 🔍 Regularly assess and review permissions: Perform regular assessments of file and directory permissions using the
ls -l
command to ensure alignment with the principle of least privilege. - ⛔ Avoid granting unnecessary write permissions: Be cautious when granting write permissions with chmod 755. Limit write access to authorized individuals or groups using the
chmod go-w file_name
command. - 👥 Implement user and group restrictions: Leverage user and group ownership using the chown command to restrict access to sensitive files or directories. For example,
chown owner:group file_name
. - ⚠️ Consider the implications of execute permissions: Evaluate the necessity of executable permissions with chmod 755 and restrict accordingly using
chmod -x file_name
if not required. - 📝 Monitor and log permission changes: Implement logging mechanisms to track chmod 755 changes and regularly review logs using
tail -f log_file
to ensure consistency and detect unauthorized modifications. - 🔒 Implement secure file and directory ownership: Assign appropriate ownership using chown to prevent unauthorized access and modifications. For example,
chown owner:group file_name
. - 🔄 Regularly update and patch your system: Keep your Linux system up to date with the latest security patches and updates using package management tools like
apt-get
oryum
. - 🔐 Enforce strong user authentication: Implement strong user authentication mechanisms, such as password policies, multi-factor authentication, or key-based authentication, using tools like
passwd
orssh-keygen
.
Comparison of Common chmod
Permissions
Here’s a quick comparison of different chmod
permission settings, their use cases, and the performance and security implications of each.
Permission Set | Owner | Group | Others | Performance and Security Implications |
---|---|---|---|---|
chmod 755 | Read, Write, Execute | Read, Execute | Read, Execute | Secure for files that need to be executed by everyone but only modified by the owner. |
chmod 777 | Read, Write, Execute | Read, Write, Execute | Read, Write, Execute | High risk, as anyone can modify and execute. Use with caution, especially in shared environments. |
chmod 644 | Read, Write | Read | Read | Secure for files that should not be executed, ensuring only the owner can modify. |
chmod 700 | Read, Write, Execute | No Access | No Access | Very secure, as only the owner has access. Suitable for personal or confidential files. |
chmod 600 | Read, Write | No Access | No Access | Very secure, ensuring only the owner can read and modify. |
To Sum Up
To wrap up, using the chmod 755
command in Linux is straightforward. You can use numeric representation (chmod 755 filename
) or symbolic representation (chmod u=rwx,g=rx,o=rx filename
). Both methods ensure you have full control while others can only read and execute.
To expand your knowledge further, I recommend checking out my articles on:
- Learn how to use
chmod +x
to make files executable, enhancing their usability. - Explore commands like
ls
andfind
with options to efficiently count files in directories of varying sizes. - Master
cat
,less
, andtail
commands to view and navigate through file contents, crucial for troubleshooting and managing data effectively.
Frequently Asked Questions
What is the difference between chmod 755 and chmod 777?
Can I use chmod 755 on directories as well?
How can I recursively apply chmod 755 to all files and folders within a directory?
-R
(or --recursive
) option with the chmod command. For example, use the following command: chmod -R 755 directory_name
. This command applies chmod 755 to the specified directory (directory_name
) and all its files and subdirectories. Exercise caution when using the -R
option, as it will affect the permissions of all nested files and directories.Is it possible to revert the permissions set by chmod 755?
chmod go-rwx file_name
to remove the read, write, and execute permissions for the group (g) and others (o), while retaining the owner’s permissions. This effectively eliminates write and execute permissions for the group and others, leaving only the owner with read, write, and execute permissions. Make sure to specify the correct file name and verify the resulting permissions to ensure they align with your desired configuration.