What are the three permission groups in Linux and what do they mean?
Owner: the user who owns the file; Group: users in the file's assigned group; Others: everyone else on the system. Each group has separate r/w/x bits.
Video Summary
Linux File Permissions in 5 Minutes | MUST Know!
Main takeaways
01
Linux permissions use three groups — owner, group, others — each with read (r), write (w) and execute (x) bits.
02
Use ls -l to view permissions; the first character shows file (‑) or directory (d).
03
chown changes file owner and group (sudo chown user[:group] file).
04
chmod sets permissions numerically (r=4, w=2, x=1); combine per group to form codes like 644 or 755.
05
Common baselines: files 644, directories 755; lock sensitive keys to 400.
Key moments
Questions answered
How do you view detailed permissions for files and directories?
Run ls -l in the terminal. The output shows file type (d or -) then three sets of rwx permissions for owner, group, and others.
How does the numeric chmod system map to permissions?
Assign values r=4, w=2, x=1 for each group. Sum them per group to form a three-digit code (owner, group, others), e.g., 644 or 755.
What are recommended baseline permissions for files, directories, and sensitive keys?
Files: 644 (owner rw, others r). Directories: 755 (owner rwx, others rx to list/enter). Sensitive key files: 400 (owner read only).
Understanding Linux File Permissions 00:18
"To be a competent Linux user, you need to understand file permissions."
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Linux file permissions define who can access or modify files and directories on your system.
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There are three core permission groups: owner, group, and others, each with distinct permissions.
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Permissions are designated as read (r), write (w), and execute (x), and they determine what each user or group can do with a file or directory.
How to View Permissions in Linux 00:50
"Use the 'ls -l' command to see details about files and directories."
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The command
ls -ldisplays detailed information, including permissions, about files and directories within a specified path. -
The first character in the output indicates whether the item is a file (-) or directory (d).
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Following these characters, you'll find three sets of permissions: owner permissions, group permissions, and permissions for everyone else.
Changing Ownership with Chown 02:50
"The 'chown' command allows you to change the owner of a file or directory."
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The
chowncommand enables you to assign a different owner or group to a file or directory in Linux. -
This command syntax involves specifying the new owner followed by the file or directory name.
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Example:
sudo chown Travis myconfig.yamlchanges the owner of 'myconfig.yaml' to user 'Travis'.
Modifying Permissions with Chmod 03:45
"The 'chmod' command enables you to change file permissions."
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The
chmodcommand modifies the permission settings of files or directories using either symbolic or numeric representation. -
Permissions are represented in a numerical format: read (4), write (2), and execute (1).
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Common permission settings include
644for files, allowing the owner read/write permissions while others can only read, and755for directories, which permits execution for all users to list contents.
Common Permission Settings 05:03
"A baseline for file permissions should be 644, while directories typically use 755."
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Standard practices dictate file permissions of
644allow the owner to read/write, while others have read-only access. -
For directories,
755is the norm, enabling the owner full access while allowing others read and execute permissions to navigate the directory. -
For sensitive files like key pairs, a setting of
400ensures only the owner can read the file, enhancing security.