AIUR NODE LAB

CCNA / RHCSA Lab — Linux & Proxmox Command Cheat Sheet

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Updated: 2026-10-23
Basis: Proxmox/VM build guide, PVE02 handoff, October 22 handoff, and Phase 5 work.
Labels: USED = actually documented in lab work; REFERENCE = useful extra explanation or check, not necessarily executed.

Safety: The Rocky instructor desktop, Rocky VMs, Ubuntu VMs, and Proxmox hosts have different network tools/configurations. Do not run guest nmcli configuration on Proxmox, or copy one VM's IP to another. Commands changing interfaces can disconnect management access. Keep PVE01 .10 and PVE02 .13 on vmbr0/nic0 until a reviewed migration plan is ready.

1. USB Cisco console access from the Rocky Linux desktop

Command / key What it does Why we used it Scope
sudo minicom -D /dev/ttyUSB0 -b 9600 Opens a 9600-baud serial session over USB adapter ttyUSB0. Accessed Cisco CLI before switch management SSH existed. USED
ls -l /dev/serial/by-id/ Lists stable USB serial adapter identities and current ttyUSBx mapping. Helps troubleshoot adapter renumbering or missing devices; documented earlier WTI work. USED (earlier phase)
Ctrl+A, then X in Minicom Closes Minicom (confirmation may appear). Exit serial console cleanly. USED

Troubleshooting: Cannot create lockfile for /dev/ttyUSB0: No such file or directory occurred when the console USB cable was unplugged. Plugging it back in resolved the problem. A serial console RJ45 jack is not an Ethernet port.

Command What it does Why we used it Scope
ip -br addr show eno1 Brief address and state view of the OptiPlex Ethernet interface. Verified desktop 192.168.100.30/24; noticed an old WTI alias. USED
ip -br link Brief link/carrier information, without IP addresses. On both Dell R320 hosts, identified nic0, nic1, vmbr0 and initial NO-CARRIER. USED
ip -br addr Brief IP list for all interfaces. Verified static addresses on Linux guests in earlier builds. USED (earlier phase)
ping -c 4 192.168.100.13 Sends four ICMP echo requests and exits. Verified PVE02 network reachability after fixing its Ethernet cable. USED
ping -c 4 -W 1 192.168.100.5 Four pings with a one-second per-reply wait. Preliminary check before allocating an access switch management IP. USED

Reading ping: 4 received / 0% loss confirms IPv4 ICMP connectivity at that time. Destination Host Unreachable means the host/path could not be reached; it does not prove the target IP is unassigned. A ping to your own IP tests the local machine, not another device.

3. Remove an unwanted temporary address

USED on Rocky instructor OptiPlex (eno1) during Phase 5:

sudo ip addr del 192.168.168.10/24 dev eno1
ip -br addr show eno1
Part Explanation
sudo Runs with administrator privileges.
ip addr del Deletes exactly the specified address from the live interface.
192.168.168.10/24 Old temporary address for WTI troubleshooting, not the actual lab management IP.
dev eno1 Targets the desktop's correct Ethernet device.

Afterward, the desktop showed only 192.168.100.30/24. Caution: ip addr del changes the current state; if a NetworkManager profile defines that address, it may return on reconnection/reboot. Persistent desktop settings were not verified during Phase 5.

4. Examine Proxmox host networking safely

ip -br link
cat /etc/network/interfaces
Command What it does Why we used it Scope
cat /etc/network/interfaces Prints the Proxmox host's network configuration file without changing it. Confirmed both hosts use vmbr0 bridged to nic0, with unique static IPs. USED
ip -br link Displays interfaces and whether they have carrier. Diagnosed PVE02 cable issue when nic0 and vmbr0 said NO-CARRIER. USED

PVE01 previously verified:

iface nic0 inet manual

auto vmbr0
iface vmbr0 inet static
    address 192.168.100.10/24
    gateway 192.168.100.1
    bridge-ports nic0
    bridge-stp off
    bridge-fd 0

iface nic1 inet manual

PVE02 same bridge layout but address 192.168.100.13/24. vmbr0 is a Linux bridge shared with the existing VMs, while nic0 is its physical uplink. The 192.168.100.1 gateway was configured in the file but not verified reachable. We did not change these settings in Phase 5.

Lesson learned: NO-CARRIER means the NIC does not detect a physical Ethernet link. PVE02's link came up after changing the Ethernet cable; no IP or bridge reconfiguration was required.

5. Rocky Linux guest networking with NetworkManager (earlier VM work)

Inspect first — USED:

nmcli -f NAME,UUID,DEVICE connection show
nmcli -f GENERAL.CONNECTION device show ens18
ip -br addr
Command What it does Why we used it
nmcli connection show Lists saved NetworkManager profiles. Identified which profile to modify on Rocky VMs.
nmcli -f NAME,UUID,DEVICE connection show Shows profile name, unique ID and active device. Prevented deleting/modifying the wrong duplicate profile.
nmcli -f GENERAL.CONNECTION device show ens18 Shows the active profile associated with guest Ethernet. Found that the actual active PVE01 Rocky profile was Wired connection 1.

USED pattern on PVE01 VM 100 (Student 1):

sudo nmcli connection modify "Wired connection 1" ipv4.method manual ipv4.addresses 192.168.100.11/24 connection.interface-name ens18 connection.autoconnect yes
sudo nmcli connection up "Wired connection 1"
ip -br addr

USED on VM 101: Same commands but address 192.168.100.12/24 on its own guest. The IP became persistent after the correct active profile was modified.

Setting Why
ipv4.method manual Uses static IP settings rather than DHCP.
ipv4.addresses .../24 Allocates that VM's unique address and subnet.
connection.interface-name ens18 Associates the profile with the actual guest NIC.
connection.autoconnect yes Activates the saved profile automatically in normal boots.
nmcli connection up ... Activates the edited profile now.

Avoid the old mistake: We initially edited an inactive or duplicate ens18 profile, and the address disappeared after reboot. Verify which profile has DEVICE ens18 before modifying it. Do not assume PVE02 VMs 200 and 201 already have .21 and .22: those were planned, not confirmed configured in the handoff.

6. Temporary vs. persistent IP assignments

USED in earlier guest troubleshooting:

sudo ip addr add 192.168.100.11/24 dev ens18

This adds an IP to a live NIC for a quick test, but is not a persistent replacement for a NetworkManager profile or Ubuntu Netplan. Only use an IP confirmed free and appropriate for that particular VM.

Duplicate-profile cleanup pattern (documented in earlier guide):

nmcli -f NAME,UUID,DEVICE connection show
sudo nmcli connection delete uuid <INACTIVE-UUID-HERE>

The second command is a template, not a literal ready-to-paste command. Only delete an independently verified inactive UUID; a wrong UUID can disconnect the VM.

7. Ubuntu guest networking with Netplan (earlier PVE02 work)

PVE02 VM 202 used the following verified Netplan file at /etc/netplan/01-lab-network.yaml:

network:
  version: 2
  renderer: networkd
  ethernets:
    ens18:
      dhcp4: false
      addresses:
        - 192.168.100.23/24
Command What it does Why we used it Scope
sudo nano /etc/netplan/01-lab-network.yaml Opens configuration file for editing. Created the Ubuntu server's static IP settings. USED
sudo chmod 600 /etc/netplan/01-lab-network.yaml Restricts file access to its owner. Cleared Netplan's file-permission warning. USED
sudo netplan generate Checks/builds backend network configuration. Validated file before activating it. USED
sudo netplan apply Applies Netplan settings. Brought guest ens18 online with .23. USED
ip -br addr Confirms actual interface/IP after applying. Saw ens18 up with .23/24. USED
ping -c 4 192.168.100.13 Tests reachability to PVE02 host. Previously succeeded from Ubuntu VM 202. USED

Caution: VM 202's reboot persistence has not yet been reverified. Proxmox management uses /etc/network/interfaces, not the guest's Netplan file.

8. Linux hostname, users, and admin access (earlier PVE02 work)

Command What it does Why we used it Scope
hostnamectl Displays the host's system hostname and OS metadata. Verified the correct Rocky/Ubuntu VM identity. USED
sudo hostnamectl set-hostname rocky-serverb02.lab.test Sets VM 201's hostname. Corrected an accidentally duplicated hostname. USED
su - Starts a full root login shell if you know root credentials. Used on VM 201 when student2 initially lacked sudo. USED
usermod -aG wheel student2 Adds student2 to administrative wheel group without removing other groups. Repaired sudo access on VM 201. USED
sudo <command> Runs a command with elevated privileges if authorized. Administered guests without working directly as root. USED

After usermod -aG wheel student2, we logged out completely and back in so the group membership applied to the session. Ensure VM hostnames are unique before enabling DNS; PVE01 VM 101 and PVE02 VM 200 were historically both named rocky-server02.

9. Proxmox VM inventory and management checks

Command What it does Why useful Status
qm list Lists VMs registered on the current Proxmox host and their state. Will be the first Phase 6 verification for VMs 100–102 and 200–202. USED in earlier build; planned again for Phase 6
qm status 100 Reports runtime status of VM 100 on its host. Helps check power state before entering console. USED in earlier build
pvesh get /nodes/pve01/qemu Queries PVE01 VM inventory via Proxmox CLI/API. Was used when VMs did not appear in a stale browser sidebar. USED in earlier build

Browser URLs verified in Phase 5:

Both logged in successfully from the Rocky desktop after Cisco connectivity was established. The hosts are independent, not a Proxmox cluster. No VM NIC VLAN tags were changed during Phase 5.

10. Mini diagnostic checklist

  1. Physical connectivity: ip -br link (Linux), show interfaces ... status (Cisco). If no carrier, check cable, correct port, and lights before rewriting config.
  2. Correct host address: ip -br addr (Linux), show ip interface brief (Cisco).
  3. Correct VLAN: show interfaces ... switchport and show interfaces trunk (Cisco).
  4. Reachability: ping -c 4 <correct-IP> from a different device.
  5. Service: Open the Proxmox HTTPS URL or verify SSH only after IP reachability is known.
  6. Persistence: Verify NetworkManager/Netplan configs on guests and copy running-config startup-config on Cisco. A successful temporary ip addr add is not a persistent configuration.

11. Phase 6 boundaries

CCNA & RHCSA training lab — training equipment only, nothing production. Internal lab addresses are private (RFC1918) by design.