Table of contents
Introduction
The multi-user capability of Unix-like systems is a feature that is deeply ingrained into the design of the operating system.
File Permissions
On a Linux system, each file and directory is assigned access rights for the owner of the file.
You can check the permission settings with ls -l.
$ ls -l
drwxr-xr-x. 13 root root 1027 Jan 3 12:32 bin/cat
Let's explore what drwxr-xr-x. 13 root root 1077 Jan 3 12:32 bin/cat means one by one.
| Command | Meaning |
|---|---|
| d | File Type |
| rwxr-xr-x. | File Mode |
| 13 | Number of links |
| root | The owner of the file |
| root | The group the file belongs to |
| 1027 | Size of the file |
| Jan 3 12:32 | Time Stamp |
| bin/cat | The name of the file/directory |
File Type
| Command | File Type |
|---|---|
| - | File |
| d | Directory |
| l | Symbolic Link |
File Mode
The r letter means the user has permission to read the file/directory. The w letter means the user has permission to write the file/directory. And the x letter means the user has permission to execute the file/directory.
| Command | Meaning |
|---|---|
| r | read |
| w | write |
| x | execute |
| - | not allowed |
Let's take a look at the 9 letters in the command.
The first 3 letters show the permissions for the file owner, the second 3 letters show the permissions for the group owner and the last 3 letters show the permissions for other users.
rwx/ r-x/ r-x/
Owner: rwx
Group: r-x
Users: r-x
Change File Modes
The chmod command is used to change the permissions of a file or directory.
Octal Mode
Each permission may be specified with an octal number: read = 4; write = 2; execute = 1; no permission = 0.
| Meaning | Number |
|---|---|
| read(r) | 4 |
| write(w) | 2 |
| execute(x) | 1 |
Example
The command below means giving permissions to read(4), write(2) and execute(1) to the owner and permissions to read(4) and execute(1) to the group user and permissions to read(4) to other users.
chmod 754 myfile
Symbolic Mode
The below is the basic syntax of chmod.
% chmod who operator permission filename
You can use the following commands to change modes.
| Command | Meaning |
|---|---|
| u(user) | user access |
| g(group) | group access |
| o(other) | other access |
| a(all) | user, group, and other access |
| Command | Meaning |
|---|---|
| + | add specified permissions |
| - | remove specified permissions |
| = | set the specified permissions |
Example
In the following example, read permission are taken away from others.
% chmod o-r filea
In the following example, read and execute permissions are added for user, group, and others.
$ chmod a+rx fileb
In the following example, read, write, and execute permissions are assigned to the group.
$ chmod g=rwx filec
Top comments (87)
When it comes to Linux I make it a point to read even intro level articles like this one. Why? 'cause I am constantly learning new things, like I did here.
Thank you for this. Keep up the good posting!
Thank you for your kind words!
If you really want to get into powerful permissioning systems, take a look at extended filesystem access control lists (via the
setfaclandgetfaclutilities), extended attributes (xattrs managed via thechattrandlsattrcommands) and, the ultimate cause of headaches, SELinux.If you're running an Internet-facing system, these are all security-extensions that you want to be reasonably well versed in.
There's also suid/sgid permissions. Normally, when you execute a program, it will run as the user which called it. suid will instead run the program as the owner of the file. For example, if you are logged in as user
developerand try to execute a suid program owned byroot, it will execute asrootinstead ofdeveloper.su,sudo,passwdrely on suid to work.The extension to suid-/sgid-enabled operations being that, when you run auditing services on a system, actions are logged both by actual executing-user and effective executing user.
Understanding Linux permissions is crucial for security and efficiency. Your insights simplify a complex topic, empowering users to manage files effectively. I diagnose and repair technical errors with great accuracy. Just as mastering Linux permissions enhances system control, resolving Canon Printer errors like Support Code 5100 and Error 5200 ensures seamless printing.
If you’re encountering a Canon printer support code 5100 or Canon error 5200, these issues typically relate to problems with the printer’s printhead or ink system. The Canon printer support code 5100 often appears when there is a paper jam, an obstruction, or if the printhead has become misaligned or clogged. To resolve this, turn off the printer, carefully check for any paper or debris blocking the printhead, and gently clean the printhead with a soft cloth. After ensuring there are no blockages, restart the printer to see if the issue persists.
On the other hand, Canon error 5200 usually occurs due to issues with the ink cartridges or printhead. This error can sometimes appear when the ink cartridge is improperly installed or when there is insufficient ink. Try removing and reinstalling the ink cartridges to ensure they are properly seated in place. Additionally, check the printer for any other obstructions that may be causing the error.
If neither solution works for your Canon printer support code 5100 or Canon error 5200, updating the printer’s firmware or contacting Canon’s support team for further assistance may be necessary. By addressing these common issues promptly, you can restore your printer to its normal functioning.
From what I know, I guess you can forgo "a" in the "a+rx".
Thank you for sharing your knowledge:)!
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By following these steps, you should be able to resolve NFL live streaming problems on YouTube TV, NFL login problems, YouTube TV app crashes, and the YouTube TV black screen issue.
This concise guide on Linux permissions provides essential insights for users. Demystifying the intricacies, it empowers individuals to navigate and control their system effectively. A valuable resource for anyone seeking clarity on the nuanced world of Linux permissions. TC Lottery MOD APK
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Your deep dive into Linux permissions is truly inspiring! Understanding file types, modes, and access levels empowers users to navigate Linux efficiently. I am skilled in identifying and correcting technical disruptions. Just as Linux permissions dictate file accessibility, resolving HP printer errors like 49.38.03 and 59.F0 ensures seamless device functionality.
Encountering HP printer errors like 49.38.03 error, 59.F0 error, E0 error, or E4 error can be frustrating, especially when you're in the middle of an important printing task. These error codes generally point to different issues within the printer's system, but there are a few effective ways to troubleshoot and fix them.
The 49.38.03 error in hp is commonly associated with an issue related to firmware or a corrupted print job in the printer's memory. To resolve this, try turning off your printer and unplugging it for a few minutes before powering it back on. This helps clear the printer's memory. If this doesn’t work, you may need to update the printer’s firmware to the latest version from the official HP website. Also, make sure to clear the print queue on your computer to remove any problematic print jobs.
The HP printer 59.F0 error typically relates to a problem with the printer’s fuser or its temperature. This error may be caused by a faulty fuser unit or issues with the electrical components connected to it. Start by turning off the printer, waiting for a few minutes, and then turning it back on. If the problem persists, inspect the fuser for any damage or misalignment. In some cases, replacing the fuser may be necessary.
If you encounter an HP printer E0 error, this often indicates a hardware failure, particularly related to the printer’s motor or power supply. Try restarting your printer and checking if the error clears. If not, you may need to perform a hard reset or check the wiring connections. If the issue is not resolved, professional assistance may be required.
Similarly, the HP printer E4 error usually appears when there’s an issue with the paper feed mechanism. This could be due to a paper jam, dirty rollers, or an obstruction within the printer. To fix this, power off the printer, open the paper tray, and check for any jammed paper or debris. Cleaning the rollers might also help clear this error.
While these errors can be troublesome, following these troubleshooting steps for the 49.38.03 error, hp 59.F0 error, E0 error, and E4 error should help restore your printer to proper working order. However, if the issues persist, consider reaching out to HP customer support for further assistance and repairs.
Your insightful article on Linux Permissions is both inspiring and educational, making complex concepts accessible. Understanding permissions empowers users to manage security effectively.
For those navigating HP Envy printer issues, mastering troubleshooting is just as essential as understanding Linux permissions. Learn how to resolve common HP Envy 4500, 4520, 5530, and 6000 printing problems in my latest blog.
If your HP Envy 4500 will not print, HP Envy 4520 will not print, HP Envy 5530 will not print, or HP Envy 6000 printer not printing, you are not alone. These are common issues faced by users, but with a few simple troubleshooting steps, you can get your printer back to working properly.
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Next, check the printer queue on your computer. Sometimes, pending print jobs can block new tasks from being processed. Clear any old or stuck print jobs from the queue to see if that resolves the issue.
Another potential cause for the HP Envy 4500 will not print, HP Envy 4520 will not print, HP Envy 5530 will not print, or HP Envy 6000 printer not printing problem is low or empty ink cartridges. Ensure that your printer has sufficient ink and that the cartridges are properly installed.
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