Welcome to Day 5, where we enter the secret lair of Linux file permissions and uncover magical artifacts like SUID, SGID, and the legendary Sticky Bit.
By the end of today, I half expected my Linux box to start chanting spells.
📚 Table of Contents
- Today’s Lab of Doom
- Challenge Breakdown
- Spellbook of the Day
- What I Learned (aka Lessons from the School of Bashcraft)
- RHCSA Objectives Crushed Today
- TL;DR
- Coming Tomorrow — Day 6
Today’s Lab of Doom
I created shared directories. I tested who could delete what. I accidentally gave a file SUID powers and it felt like I’d handed a toddler the root password.
Challenge Breakdown
- Create a shared folder for a group
- Add the SGID bit so group inheritance works
- Set the Sticky Bit so users stop deleting each other’s stuff
- Play with SUID on files (but not for evil)
- Review file permissions like a digital detective
Spellbook of the Day
mkdir /sysops_team - We're making a shared workspace — like a digital whiteboard everyone can write on.
chown :devops_team /sysops_team - Assigns the group ownership to devops_team, so all group members have access.
chmod 2775 /shared_team - This ensures any file created inside /sysops_team will automatically belong to devops_team, keeping things tidy and collaborative.
chmod +t /sysops_team - Prevents team sabotage! Only the person who created a file (or root) can delete it, even though everyone can write in the directory.
chmod u+s /usr/bin/passwd - This lets regular users change their passwords because passwd runs with root’s power, even though they’re not root. Use with caution!
ls -l /shared_team - The inspection tool! This reveals whether your SGID and Sticky Bit are set correctly, and lets you marvel at your sysadmin wizardry (or lack of in this case!)
What I Learned (aka Lessons from the School of Bashcraft)
SGID = “Group loyalty forever!” Files created in that folder will inherit the group.
Sticky Bit = “You can’t delete my files, Karen.” Only the file owner (or root) can delete.
SUID = “Run me as the file’s owner.” Mostly used on programs like passwd. Don't mess this up unless you're aiming for hacker-of-the-month.
Watching ls -l change after each permission tweak is like checking the weather during a storm.
RHCSA Objectives Crushed Today
Manage special permissions like SUID, SGID, and Sticky Bit
Understand secure collaboration through group permissions
Level up in terminal-based trust issues
TL;DR
Today I learned that Linux file systems have more trust issues than my last team project in university. But at least chmod doesn’t ghost you.
Coming Tomorrow — Day 6
Mountains, Devices & Eternal Confusion
(AKA: "Why does my USB drive disappear when I sneeze?")
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