> ## Documentation Index > Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Demo Working With Linux File System Permissions > Guide to creating users and groups, assigning file ownership with chown, and managing permissions using numeric and symbolic chmod, with verification using ls -l In this lesson you'll apply Linux file system permissions in a practical sequence: create users and groups, assign ownership, and use both numeric and symbolic forms of `chmod`. The objective is not just to run commands, but to understand how each change affects access control so you can enforce proper policies on a Linux system. The image is a dark presentation slide titled "Working With Linux File System Permissions." It also shows a simple blue outline icon of a file with code brackets and a padlock, suggesting locked or secured files. What you'll learn * Create users and groups, and add users to a group. * Change ownership with `chown` (including `-R` for recursion). * Set permissions with numeric `chmod` (e.g., `640`) and symbolic `chmod` (e.g., `g+w`, `o-rwx`). * Verify results with `ls -l`. Numeric permission shorthand: 6 = read+write (rw), 4 = read (r), 2 = write (w), 1 = execute (x), 0 = no permissions. Example: `640` → owner `rw` (6), group `r` (4), others `-` (0). Prerequisites * You will run the commands as root (prompt shown as `root@control:/#`). If you are not root, prefix admin commands with `sudo`. * Basic familiarity with the shell and `ls -l` output is helpful. Step-by-step demo Run the following commands in order. Explanations follow each section. Create users and a group, then add users to the group: ```bash theme={null} root@control:/home# useradd dev1 root@control:/home# useradd dev2 root@control:/home# useradd manager root@control:/home# groupadd devteam root@control:/home# usermod -aG devteam dev1 root@control:/home# usermod -aG devteam dev2 ``` * We created three accounts: `dev1`, `dev2`, and `manager`. * We created a shared group `devteam` and appended `dev1` and `dev2` to it using `usermod -aG`, which preserves existing group memberships. Create a project directory and a config file, then set ownership: ```bash theme={null} root@control:/# cd / root@control:/# mkdir project root@control:/# touch /project/app.conf root@control:/# chown dev1:devteam /project/app.conf root@control:/# ls -l /project total 0 -rw-r--r-- 1 dev1 devteam 0 Apr 20 16:03 app.conf ``` * `chown dev1:devteam /project/app.conf` assigns the file owner to `dev1` and group to `devteam`. * `ls -l` confirms owner and group: `dev1 devteam`. Set permissions so owner can read/write, group can read, others have none (numeric `chmod 640`): ```bash theme={null} root@control:/# chmod 640 /project/app.conf root@control:/# ls -l /project total 0 -rw-r----- 1 dev1 devteam 0 Apr 20 16:03 app.conf ``` * `chmod 640` sets owner = `rw` (6), group = `r` (4), others = `-` (0). The `ls -l` permission display shows `-rw-r-----`. Create a second file and apply ownership recursively: ```bash theme={null} root@control:/# touch /project/app2.conf root@control:/# ls -l /project total 0 -rw-r----- 1 dev1 devteam 0 Apr 20 16:03 app.conf -rw-r--r-- 1 root root 0 Apr 20 16:06 app2.conf root@control:/# chown -R dev1:devteam /project root@control:/# ls -l /project total 0 -rw-r----- 1 dev1 devteam 0 Apr 20 16:03 app.conf -rw-r--r-- 1 dev1 devteam 0 Apr 20 16:06 app2.conf ``` * When `app2.conf` was created, defaults gave it owner `root:root`. * `chown -R dev1:devteam /project` recursively changes owner and group for the directory and its contents to `dev1:devteam`. Add group write permission to `/project/app.conf` using symbolic `chmod`: ```bash theme={null} root@control:/# chmod g+w /project/app.conf root@control:/# ls -l /project total 0 -rw-rw---- 1 dev1 devteam 0 Apr 20 16:03 app.conf -rw-r--r-- 1 dev1 devteam 0 Apr 20 16:06 app2.conf ``` * `chmod g+w` adds write permission for the group without changing owner or other bits. * `app.conf` now shows `-rw-rw----` (owner `rw`, group `rw`, others `-`) which corresponds to numeric `660`. Remove any privileges from others explicitly: ```bash theme={null} root@control:/# chmod o-rwx /project/app.conf root@control:/# ls -l /project total 0 -rw-rw---- 1 dev1 devteam 0 Apr 20 16:03 app.conf -rw-r--r-- 1 dev1 devteam 0 Apr 20 16:06 app2.conf root@control:/# ``` * `chmod o-rwx` removes read, write, and execute bits from others. If others already had no permissions, the state remains unchanged. Quick reference — common numeric values | Numeric | Symbolic | Meaning | | -: | - | - | | `700` | `rwx------` | Owner full, group/others none | | `750` | `rwxr-x---` | Owner rwx, group rx, others none | | `640` | `rw-r-----` | Owner rw, group r, others none | | `660` | `rw-rw----` | Owner rw, group rw, others none | | `644` | `rw-r--r--` | Owner rw, group r, others r | Commands summary | Command | Purpose | | - | - | | `useradd ` | Create a new user account | | `groupadd ` | Create a new group | | `usermod -aG ` | Add `` to supplementary `` without removing other groups | | `chown user:group ` | Change owner and group of a file | | `chown -R user:group ` | Recursively change owner/group for a directory and its contents | | `chmod ` | Set file mode using numeric (e.g., `640`) or symbolic (e.g., `g+w`) forms | | `ls -l` | List files with owner/group and permission bits | Best practices and warnings Use `chown -R` and recursive `chmod` with care — they can change ownership/permissions for many files at once. Double-check the target path to avoid inadvertently changing system or unrelated files. Further reading * `man chmod` — [https://man7.org/linux/man-pages/man1/chmod.1.html](https://man7.org/linux/man-pages/man1/chmod.1.html) * `man chown` — [https://man7.org/linux/man-pages/man1/chown.1.html](https://man7.org/linux/man-pages/man1/chown.1.html) * Practical guide on Linux file permissions — [https://www.digitalocean.com/community/tutorials/understanding-linux-file-permissions](https://www.digitalocean.com/community/tutorials/understanding-linux-file-permissions) Summary * Created users and a shared group, then added users to that group. * Created files, set ownership with `chown` and `chown -R`. * Used numeric `chmod` (e.g., `640`) to explicitly set owner/group/others bits. * Used symbolic `chmod` (`g+w`, `o-rwx`) to tweak permission classes without altering other bits. * Verified each step with `ls -l` to confirm ownership and permissions. 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