Appendix — Troubleshooting Common Beginner Problems¶

What you'll learn: how to read an error message calmly and fix the dozen problems that trip up almost every beginner — permission errors, missing commands, unreachable lab hosts, broken wordlists, proxy and certificate headaches, clock skew, and hanging scans. Prerequisites: any chapter — keep this open in a tab while you work. ⬅️ Course index

This is the "why isn't it working?" page. Nothing here is your fault — every one of these has happened to everyone. The trick is always the same: read the actual error, match it to a row below, apply the fix. No shame, just steps.

Permissions — "Permission denied" / "you must be root"¶

Many scans and system tools need root because they touch raw network sockets or protected files. Borrow root with sudo — but not everything needs it (a plain nmap -sT runs as the normal kali user).

Symptom	Likely cause	Fix
`Permission denied` running a tool	Tool needs root	Put `sudo` in front
nmap: `You requested a scan type which requires root privileges`	`-sS` (SYN) and `-O` (OS detect) need raw sockets	Run `sudo nmap ...`
`bash: ./script.sh: Permission denied`	Script isn't executable	`chmod +x script.sh` then `./script.sh`
Can't write to `/usr/share/...`	Owned by root	`sudo` the command, or work in `~`

sudo nmap -sS -O 192.168.56.20      # SYN scan + OS detection need root
chmod +x loot.sh && ./loot.sh       # make your own script runnable

"command not found"¶

The tool either isn't installed, or your package list is stale. Update first, then install.

Symptom	Likely cause	Fix
`command: not found` for a Kali tool	Not installed (Kali ships lean now)	`sudo apt install <pkg>`
Python tool missing (`impacket`, `certipy`)	Installed via pipx, not apt	`pipx install <tool>`
Tool only exists on GitHub	Niche/newer tool	`git clone <url>` then read its README
`apt install` says Unable to locate package	Package list is stale	`sudo apt update` first, then retry

sudo apt update                     # ALWAYS refresh the list first
sudo apt install seclists nikto     # install from Kali's repo
pipx install impacket               # Python security tools
apt search <partial-name>           # can't find it? check the spelling

Can't reach a lab host — `No route to host`, ping fails¶

This is the single most common lab problem, and it's almost always the VirtualBox network setting, not the tool.

Symptom	Likely cause	Fix
`No route to host` / `Destination unreachable`	VM's network is NAT/Bridged, not host-only	Set the adapter to Host-only (`vboxnet0`) on both VMs
`ping 192.168.56.20` times out	Target VM is powered off	Start Metasploitable2 / the DC in VirtualBox
Kali has no `192.168.56.x` address	Host-only adapter missing or down	Check `ip a`; add the adapter in VM settings
Reachable, but a port is refused	Host firewall (common on the Windows DC)	Expected — try another service/port

ip a          # do you have an inet 192.168.56.10 on the host-only NIC?
ip r          # is there a route for 192.168.56.0/24?
ping 192.168.56.20   # Ctrl+C to stop

If ip a shows no 192.168.56.x address on Kali, the fix is in VirtualBox → VM Settings → Network: set Adapter to Host-only Adapter, name vboxnet0. See 03 — Networking basics and ../labs/topology.md.

Wordlists — rockyou is missing¶

Kali ships rockyou.txt compressed to save space. You unzip it once.

Symptom	Likely cause	Fix
`rockyou.txt: No such file or directory`	It's still gzipped as `.gz`	`sudo gunzip /usr/share/wordlists/rockyou.txt.gz`
Want more lists (users, subdomains)	SecLists not installed	`sudo apt install seclists`

sudo gunzip /usr/share/wordlists/rockyou.txt.gz     # one-time, unzips in place
sudo apt install seclists                           # more lists in /usr/share/seclists

Burp Suite — browser won't load HTTPS / certificate errors¶

When Burp sits between your browser and a site, the browser sees Burp's certificate and (rightly) complains — until you tell it to trust Burp's CA.

Symptom	Likely cause	Fix
Browser: Your connection is not private on every HTTPS site	Burp's CA cert not installed in the browser	Install Burp's CA (steps below)
Nothing appears in Burp's Proxy tab	Browser isn't pointed at Burp	Set proxy to `127.0.0.1:8080`
Pages hang forever	Proxy on but Burp not running / Intercept is ON	Start Burp; toggle Intercept off

1. Set the browser proxy to 127.0.0.1 : 8080 (use FoxyProxy in Firefox).
2. With the proxy on, visit http://burp and download "CA Certificate" (cacert.der).
3. Firefox: Settings → Privacy & Security → Certificates → View Certificates →
   Authorities → Import → tick "Trust to identify websites". Full steps in [08 — Web hacking](08-web-hacking.md).

proxychains — traffic isn't being tunneled¶

proxychains only tunnels if the config points at a proxy that's actually listening on the right port.

Symptom	Likely cause	Fix
Tool connects directly, ignores the proxy	Wrong SOCKS port in the config	Edit `/etc/proxychains4.conf` to match your listener
`Connection refused` for every hop	No proxy/pivot listening yet	Start the SSH `-D` / chisel / Meterpreter SOCKS proxy first
Some UDP/ICMP tools "don't work"	SOCKS can't carry them	Use TCP-based tools (e.g. `nmap -sT -Pn`)

tail /etc/proxychains4.conf     # last line: socks5 127.0.0.1 1080 (must match your proxy)
proxychains nmap -sT -Pn 10.10.10.5      # force a TCP scan through the tunnel

Kerberos / Active Directory — `KRB_AP_ERR_SKEW` (clock skew)¶

Kerberos refuses tickets if your clock differs from the Domain Controller by more than ~5 minutes. AD is also picky about DNS — names must resolve via the DC.

Symptom	Likely cause	Fix
`KRB_AP_ERR_SKEW`, clock skew too great	Kali's time drifted from the DC	Sync Kali's clock to the DC
KDC_ERR_C_PRINCIPAL_UNKNOWN / can't find realm	Kali is using the wrong DNS	Point DNS at the DC's IP

sudo ntpdate 192.168.56.30       # sync Kali's clock to the DC (or: sudo rdate -n 192.168.56.30)
echo "nameserver 192.168.56.30" | sudo tee /etc/resolv.conf   # DNS must point at the DC

WinRM / Ansible to the Windows DC fails¶

Talking to Windows over WinRM (port 5985) needs the service enabled, correct credentials, and — for Ansible — the right transport settings.

Symptom	Likely cause	Fix
`Connection refused` on 5985	WinRM not enabled on the DC	On the DC (PowerShell, admin): `Enable-PSRemoting -Force`
`evil-winrm` / Ansible: authentication failed	Wrong user/password or domain format	Try `DOMAIN\\user` or `user@domain`, verify the password
Ansible: certificate/SSL validation error	HTTPS/cert checks on 5986	Use `ansible_winrm_server_cert_validation=ignore` for the lab

nmap -p 5985,5986 192.168.56.30                      # is WinRM even listening?
evil-winrm -i 192.168.56.30 -u Administrator -p 'Password123!'

Metasploit — `db_status` says disconnected¶

The Metasploit database (Postgres) stores hosts, services, and loot. If it's disconnected, (re)initialize it.

Symptom	Likely cause	Fix
`[*] postgresql selected, no connection`	Database not initialized/started	`sudo msfdb init`
Was working, now broken after an update	Stale DB state	`sudo msfdb reinit`

sudo msfdb init          # first-time setup
sudo msfdb reinit        # nuke & recreate if it's corrupted
msfconsole -q -x "db_status; exit"   # verify — should say "connected"

apt errors — "Could not get lock" / broken packages¶

Symptom	Likely cause	Fix
`Could not get lock /var/lib/dpkg/lock`	Another apt / auto-update is running	Wait a minute; or close the other package manager
Unable to locate package	Package list is stale	`sudo apt update` first
Install stops mid-way, packages "broken"	Interrupted install	`sudo apt --fix-broken install`

sudo apt update                     # fixes most "not found" errors
sudo apt --fix-broken install       # repair a half-finished install
sudo dpkg --configure -a            # finish configuring interrupted packages

Don't force-delete the lock file while apt is genuinely running — just wait for it to finish.

Wireless — monitor mode won't enable¶

Monitor mode needs an adapter that supports it, and no other process fighting for the interface. In a VM the adapter must be a USB Wi-Fi dongle passed through — the VM's built-in NIC can't do monitor mode.

Symptom	Likely cause	Fix
`airmon-ng` starts but capture is empty	NetworkManager grabbed the interface	`sudo airmon-ng check kill` first
No `wlan0` inside the VM	USB adapter not passed through	VirtualBox → USB → add the dongle; install its driver
Monitor mode simply refuses	Chipset doesn't support it	Use a known-good adapter (Atheros/Ralink)

sudo airmon-ng check kill           # stop NetworkManager/wpa_supplicant
sudo airmon-ng start wlan0          # creates wlan0mon
iw dev                              # confirm the monitor interface exists

nmap is slow or seems to hang¶

Symptom	Likely cause	Fix
Scan takes forever	Filtered ports make nmap wait on timeouts	Add `--min-rate 1000` or `-T4`
UDP scan never finishes	UDP is slow by nature; `-p-` makes it worse	Scan a few ports: `-sU -p 53,161,137`
"It froze"	It's still working, just quiet	Press Enter for a progress line, or add `--stats-every 10s`

sudo nmap -sS -T4 --min-rate 1000 192.168.56.20      # faster TCP scan
sudo nmap -sU -p 53,69,161 192.168.56.20             # targeted UDP, not -p-

Tool runs fine but returns "no results"¶

Nine times out of ten you scanned the wrong host or interface — a typo'd IP, a target that's off, or you're on the NAT NIC instead of host-only.

Symptom	Likely cause	Fix
Empty output, no errors	Wrong target IP	Re-check the address; confirm the VM is up with `ping`
Nothing found on the lab subnet	You're bound to the wrong interface	`ip a` — confirm you have `192.168.56.10`
Web tool finds nothing	Wrong port	Docker apps are `localhost:8081–8084`, not 80

ip a                        # which interfaces/IPs do I actually have?
ping -c1 192.168.56.20      # is the target alive before I scan it?

Golden rules¶

When something breaks, walk this list in order — it resolves the vast majority of problems:

Update first. Half of "this tool is broken" is a stale install: sudo apt update.
Read the actual error. The fix is usually in the words on screen — match them to a table above.
Check your target and interface. ip a and a quick ping catch wrong-IP / wrong-network mistakes instantly.
Use sudo when the tool asks for it — and only then. Not everything needs root.
Snapshot before anything risky. A broken Kali should be a 10-second rollback, not a reinstall.

Next¶

➡️ Back to the Course index to continue, or jump to the chapter for the tool that's misbehaving.

Sources¶

Kali Docs — General Use & FAQ: https://www.kali.org/docs/general-use/
Kali Docs — Troubleshooting: https://www.kali.org/docs/troubleshooting/
Nmap Reference Guide (timing & performance): https://nmap.org/book/man-performance.html
PortSwigger — Installing Burp's CA certificate: https://portswigger.net/burp/documentation/desktop/external-browser-config/certificate