Difference between revisions of "Introduction to Linux in HPC/Users and permissions"
Introduction to Linux in HPC/Users and permissions
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|| Explanation: Correct - only read, write and execute are file permissions in Linux. | || Explanation: Correct - only read, write and execute are file permissions in Linux. | ||
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| + | |title = Who can change the owner or group of a file? | ||
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| + | - the owner of that file | ||
| + | || Explanation: Wrong, only root can do that. | ||
| + | - everyone in this group | ||
| + | || Explanation: Wrong, only root can do that. | ||
| + | - admin (root) | ||
| + | || Explanation: Correct, only root can change the owner or group of a file with chown. | ||
</quiz> | </quiz> | ||
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Revision as of 22:41, 26 November 2020
| Tutorial | |
|---|---|
| Title: | Introduction to Linux in HPC |
| Provider: | HPC.NRW
|
| Contact: | tutorials@hpc.nrw |
| Type: | Multi-part video |
| Topic Area: | HPC Platforms |
| License: | CC-BY-SA |
| Syllabus
| |
| 1. Background and History | |
| 2. The Command Line | |
| 3. Linux Directory Structure | |
| 4. Files | |
| 5. Text display and search | |
| 6. Users and permissions | |
| 7. Processes | |
| 8. The vim text editor | |
| 9. Shell scripting | |
| 10. Environment variables | |
| 11. System configuration | |
| 12. SSH Connections | |
| 13. SSH: Graphics and File Transfer | |
| 14. Various tips | |
This tutorial covers the concept of users (and groups) in the multi-user operating system Linux. It will also explain the various permissions that a file or directory can have, how to determine and change them.
Video
Quiz
Who can change the permissions of a file?
How is the top-level admin (or superuser) called in Linux?
Which one of the following is not a file permission?
Who can change the owner or group of a file?
Which command can prevent other users not in your group from writing to input.dat?
Exercises in Terminal (slide 89)
1. Create an empty file, make it read-only, make it executable.
| Answer: |
Create an empty file: touch file.txt.
make it read-only: chmod a-w file.txt; chmod a-x file.txt; chmod a+r file.txt.
make it executable: chmod a+x file.txt.
Explanation: The touch command can be used to create an empty file. In this example it is file.txt.
chmod a-w file.txt; chmod a-x file.txt; chmod a+r file.txt means to execute the three commands subsequently.
chmod a-w file.txt removes the write permission for all users.
chmod a-x file.txt removes the executable permission for all users.
chmod a+r file.txt adds the read permission for all users.
chmod a+x file.txt makes file.txt executable for all users.
|
2. Start a process (e.g. sleep 10m)
| Answer: |
Use a second console to look at it in top.
Kill it.
Hint:
To kill the started process (e.g. sleep 10m):
1. Go to the terminal that started the process.
2. Press Ctrl-C to kill it.
|
3. Start a process, bring it into background/foreground.
| Hint: |
To bring a process to background:
Press Ctrl-Z (pause the process).
Type bg (bring it to background).
To bring a process to foreground:
Type fg (bring it to foreground).
|