📄 SUNDAY REVISION SERIES

RHCSA Documents

Every Sunday, I revise one RHCSA module and post it on LinkedIn — written entirely from my own handwritten notes. This is not just revision — it is my commitment to consistency and growth.

15

Documents

Every

Sunday

RHCSA

Topic

$ ls -la drwxr-xr-x root $ pwd /home/varad $ whoami varad $ mkdir chmod grep cat Basic of Linux Commands · Filesystem · Terminal
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01

Basic Of Linux

RHCSA 1st module which holds basic commands and linux information.

RHCSA
file.txt r w x $ ls -l -rwxr-xr-x varad drwxr-xr-- root lrwxrwxrwx link -rw-r--r-- file Soft Link Hard Link FILE Editing Permissions · Links · ls -l
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02

FILE Editing

📁 file types & permissions 👥 owner, group & others 📜 ls -l for details 🔗 soft vs hard links 🛠️ permission commands.

EDIT
DEFAULT DIRECTORIES /etc Configuration files for the system /var Variable data like logs, cache, spool /bin Essential user command binaries /sbin System binaries for administration /dev Device files and special files $ ls / etc var bin sbin dev Default Directories /etc · /var · /bin · /sbin · /dev
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03

Default files in linux

📂 Linux directories meaning & purpose 🧠 real system usage ⚙️ admin importance 💻 turning commands into confidence.

Default directories.
UID: 0 ROOT UID:1-999 SYSTEM UID:1000+ NORMAL useradd usermod userdel passwd root:x:0:0:root:/root:/bin/bash User Management Root · System · Normal Users
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4.1

User Management

👤 User & UID basics 🔐 root, system & normal users ⚙️ user privileges 🧱 system vs normal difference 💻 user management commands.

RHCSA
GROUP A GROUP B GROUP ACCESS RULES ✅ Allow Access ✏️ Edit Access ❌ Deny Access groupadd devs gpasswd -a user groups varad SYSTEM POWER STORAGE DATA DENY ACCESS ALLOW ACCESS Group Management GID · groupadd · gpasswd · /etc/group
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4.2

Group Management

🐧 concept clarity 📘 groups basics 🔥 types of groups 🛠️ command practice 📄 /etc/group fields.

RHCSA
- rwx r-x r-- varad devs file.sh Owner Group Others r — Read 📖 View file content Octal: 4 w — Write ✏️ Modify content Octal: 2 x — Execute ⚡ Run the file Octal: 1 $ chmod 755 file.sh $ chmod u+x file.sh FILE Permissions
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05

FILE Permission

Information related to file permission, its various types (r,w,x). how you can allocate it to user, group & others.

RHCSA
crontab at command One-time task $ at 10:00 AM $ atq / atrm cron Repeating task * * * * * cmd crontab -e/-l min hr day mon wday command 0 2 * * 0 /scripts/backup.sh Job Scheduling
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06

Job Scheduling

Basic automation in linux os by scheduling the task using at and crontab. Basic commands and configuration of the job scheduling.

RHCSA
setfacl Set ACL rules -m u:user:rwx -m g:grp:r-x -x remove rule getfacl View ACL rules user::rwx user:bob:r-- mask::r-x 🎭 MASK USER — Effective Permission Limiter mask::r-x → user:bob:rwx becomes r-x (mask overrides!) ACL — Access Control List setfacl · getfacl · mask · fine-grained control
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07

ACL (Access Control List)

🔐 ACL basics 🎭 Mask user importance 🛠️ setfacl & getfacl usage 🔍 find command deep dive 💡 Linux tip for faster workflow ⚡

RHCSA
Application container Containers Host System namespaces cgroups SELinux Containerization kernel · namespaces · cgroups · SELinux
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08

Containerization

🐳 Containerization basics 🏗️ architecture (kernel, namespaces, cgroups, SELinux) ⚙️ solves host issues 📊 pros & limitations.

RHCSA
PODMAN Podman Features 🔐 Rootless containers 🚫 No daemon required 🐧 RHEL native tool 🔄 Docker compatible 🧩 cgroups + SELinux $ podman run -d nginx $ podman ps -a $ podman images Podman rootless · daemonless · RHEL native
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8.2

Podman

🐧 Containerization revision 📦 Podman architecture & benefits 🔐 rootless, daemonless containers 🧩 namespaces, cgroups, SELinux 🖥️ Podman Desktop usage

RHCSA
DOCKER $ docker run -d nginx $ docker ps -a $ docker build -t app . Build & Ship Fast & Light Scalable Docker Build · Ship · Run · Scale
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8.3

Docker

📄 Docker documentation done 🐳 containerization basics 🏗️ architecture (client, daemon, registry) ⚙️ step-by-step workflow ✅ advantages & ⚠️ limitations.

RHCSA
Hard Disk sda1 sda2 sda3 Linux Boot Sequence 1 BIOS/UEFI Power-on self test 2 MBR/GRUB Bootloader loads 3 Kernel Linux kernel init 4 systemd Init system starts 🖥️ Login prompt Partition Part-1 Disk layout · Boot sequence · GRUB
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9.1

Partition Part-1

🧩 Logical disk division 🔐 better data isolation 🚀 Linux boot sequence 🧠 cold vs warm boot 🛠️ kernel, GRUB & filesystem roles.

RHCSA
MBR Max 4 Primary Partitions Disk limit: 2TB 32-bit partition entries P1 P2 P3 fdisk /dev/sda lsblk / blkid GPT Up to 128 Partitions Disk limit: 9.4 ZB 64-bit partition entries P1 P2 P3 P4 ... gdisk /dev/sda parted / lsblk VS Primary Partition Extended → Logical Swap Partition Partition Part-2 MBR vs GPT · Primary · Extended · Logical
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9.2

Partition Part-2

🧩 Primary, Extended & Logical partitions ⚖️ MBR vs GPT differences 📐 partition limits & entries 🚀 smart partition planning before OS installation.

RHCSA
sudo terminal $ sudo visudo varad ALL=(ALL) ALL $ sudo su - [root@rhel ~]# $ sudo -l User may run: ALL /etc/shadow 🔐 Encrypted passwords 📅 Password aging ⏰ Min/Max days ⚠️ Warning period 🚫 Account expiry chage -l username 📋 sudoers syntax: user HOST= (runas) NOPASSWD: command Sudo & Shadow sudoers · visudo · /etc/shadow · chage
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10

Sudo & Shadow

🧾 sudoers syntax & command permissions 🧠 why visudo matters 🔒 /etc/shadow with password aging ⚠️ small misconfigurations can break security.

RHCSA
CLIENT varad@local $ ssh user@ip Connected ✓ SERVER Port 22 sshd daemon 🔐 Encrypted Tunnel Private Key Public Key $ ssh-keygen -t rsa $ ssh-copy-id user@192.168.1.10 $ scp file.txt user@server:/path/ SSH — Secure Shell key-based auth · SCP · Port 22 · sshd
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11.1

SSH (Secure Shell Access)

🔐 Secure remote access via SSH 🔑 password vs key-based auth ⚙️ TCP & key exchange basics 📂 SCP for secure transfer 🌐 role in DevOps & cloud.

RHCSA
NTP 12 6 9 3 chronyc sources timedatectl Time Sync ✓ NFS NFS Server /srv/share NFS Client mount -t nfs exportfs -rv showmount -e /etc/exports RPC service NTP & NFS chrony · timedatectl · exports · mountd
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11.2

NTP and NFS

⏱️ NTP time sync 🖥️ Chrony config 📂 NFS file sharing 🔗 RPC discovery ⚙️ remote mount like local storage.

RHCSA
/etc/passwd name:x:UID:GID:comment:home:shell root x 0 0 root:/root:/bin/bash /etc/shadow root:$6$hash:19000:0:99999:7::: /etc/group devs:x:1001:varad,alice,bob /etc/fstab /dev/sda1 / ext4 defaults 0 1 /etc/crontab 0 2 * * 0 root /scripts/backup.sh /etc/passwd /etc/shadow /etc/group /etc/fstab /etc/crontab File Fields in Linux passwd · shadow · group · fstab · crontab
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12

File Fields in linux

📁 /etc/passwd basics 🔐 /etc/shadow security 👥 group & gshadow management 💽 fstab for mounting ⏰ cron scheduling 🌐 services port mapping.

RHCSA