`lsblk`: List block devices. Trigger: New disk, partition identification. Mistake: Confusing disk names (`sda`, `nvme0n1`).

`fdisk -l`: List partition tables. Trigger: Partitioning disks. Mistake: Running `fdisk` without `-l` on an active disk.

`mount /dev/sdb1 /mnt/data`: Mount a filesystem. Trigger: Accessing new partitions, external drives. Mistake: Not creating mount point directory first.

`umount /mnt/data`: Unmount a filesystem. Trigger: Removing external drives, before disk operations. Mistake: Forgetting to unmount before removing a disk.

`cat /etc/fstab`: View static filesystem table. Trigger: Persistent mounts, boot issues. Mistake: Incorrect entries can prevent boot.

`sync`: Flush filesystem buffers. Trigger: Before reboot or power off. Mistake: Losing cached data on sudden power loss.

`fsck /dev/sdb1`: Check and repair a filesystem. Trigger: Filesystem corruption. Mistake: Running on a mounted filesystem.

`dd if=/dev/zero of=/swapfile bs=1M count=2048`: Create a swap file. Trigger: Adding more swap space. Mistake: Not setting correct permissions (`chmod 600`).

`mkfs.ext4 /dev/sdb1`: Format a partition with ext4. Trigger: Preparing new partition. Mistake: Formatting the wrong partition.

`resize2fs /dev/sdb1`: Resize an ext2/3/4 filesystem. Trigger: Expanding logical volumes. Mistake: Not resizing the underlying partition first.

7. Processes, CPU & Memory

`ps aux | grep `: List processes. Trigger: Finding specific processes. Mistake: Forgetting `aux` for all users and processes.
`top`: Interactive process viewer. Trigger: High CPU/memory usage investigation. Mistake: Not sorting by CPU/memory (`P`/`M` keys).
`htop`: Enhanced interactive process viewer (install `htop`). Trigger: More detailed process monitoring. Mistake: Forgetting to install it first.
`kill `: Terminate a process. Trigger: Stopping misbehaving processes. Mistake: Not trying `SIGTERM` (default) before `SIGKILL` (`kill -9`).
`killall `: Terminate processes by name. Trigger: Stopping all instances of a service. Mistake: Accidentally killing too many processes.
`nice -n 10 `: Run command with lower priority. Trigger: Running background tasks without impacting foreground. Mistake: Not understanding `nice` values (lower number = higher priority).
`uptime`: System load averages. Trigger: Quick check of CPU utilization. Mistake: Interpreting load average incorrectly (e.g., 1.0 on 4-core system).
`lsof -i :`: List processes using a specific port. Trigger: "Address already in use" errors. Mistake: Forgetting `sudo`.
`lsof `: List processes using a file. Trigger: File lock issues, "Text file busy" errors. Mistake: Not using `sudo` for system files.

8. Security Quick Checks

`sudo passwd -l `: Lock a user account. Trigger: Suspected compromise, temporary disabling. Mistake: Not unlocking after investigation.
`sudo passwd -u `: Unlock a user account. Trigger: Re-enabling a locked user. Mistake: Forgetting to reset password after unlock.
`last`: Show last logged in users. Trigger: Audit log, suspicious activity. Mistake: Not checking `lastb` for failed login attempts.
`who`: Show current logged in users. Trigger: See who is on the system. Mistake: Assuming all listed users are legitimate.
`w`: Show who is logged on and what they are doing. Trigger: Quick overview of system activity. Mistake: Misinterpreting idle times.
`find / -perm /4000 -o -perm /2000 2>/dev/null`: Find SUID/SGID files. Trigger: Identifying potential privilege escalation vectors. Mistake: Not regularly auditing these.
`grep -Rn 'PermitRootLogin yes' /etc/ssh/sshd_config`: Check f