889 commands · 48 cheat sheets · 6 subcategories

Linux master quick reference — Page 4

Browse 226 commands from 12 focused cheat sheets on page 4 of 4. Each example opens its matching detailed section.

Networking and Connectivity · 18 commands

iproute2 Routing and Traffic Control Cheat Sheet

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UseSyntaxExamples
Show concise addressesip -brief address showView examples
Export routes as JSONip -json route show table allView examples
Resolve an IPv4 pathip route get 203.0.113.10 from 192.0.2.20View examples
Resolve an IPv6 pathip -6 route get 2001:db8:2::10 from 2001:db8:1::20View examples
Show the main tableip route show table mainView examples
Replace a route idempotentlysudo ip route replace 198.51.100.0/24 via 192.0.2.1 dev \ eth0 metric 100View examples
Delete an exact routesudo ip route del 198.51.100.0/24 via 192.0.2.1 dev eth0 \ metric 100View examples
Show policy rulesip -details rule showView examples
Add a source policysudo ip rule add priority 1000 from 192.0.2.0/24 table \ 100View examples
Add a policy-table defaultsudo ip route replace default via 192.0.2.1 dev eth0 \ table 100View examples
Monitor network changesip monitor link address route ruleView examples
Show neighbor stateip -details neighbor show dev eth0View examples
Flush failed neighborssudo ip neighbor flush dev eth0 nud failedView examples
Show queue disciplinestc -s qdisc show dev eth0View examples
Install fq_codel root qdiscsudo tc qdisc replace dev eth0 root fq_codelView examples
Add lab delay and losssudo tc qdisc replace dev veth-test root netem delay \ 50ms loss 0.1%View examples
Remove a root qdiscsudo tc qdisc del dev veth-test rootView examples
Show iproute2 versionip -VersionView examples

Networking and Connectivity · 20 commands

Linux DNS Resolution and Resolver Tools Cheat Sheet

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UseSyntaxExamples
Resolve through NSSgetent ahosts example.comView examples
Inspect hosts lookup ordergrep -E '^[[:space:]]*hosts:' /etc/nsswitch.confView examples
Identify resolv.conf ownerreadlink -f /etc/resolv.confView examples
Show resolver directivesgrep -E \ '^[[:space:]]*(nameserver|search|domain|options)[[:space:]]' \ /etc/resolv.confView examples
Query an A recorddig example.com A +noall +answerView examples
Query an AAAA recorddig example.com AAAA +noall +answerView examples
Query one DNS serverdig @192.0.2.53 example.com A +noall +answer +commentsView examples
Run a reverse lookupdig -x 192.0.2.25 +noall +answerView examples
Retry DNS over TCPdig +tcp @192.0.2.53 example.com AView examples
Trace delegationdig +trace www.example.comView examples
Show effective DNS policyresolvectl statusView examples
Query through systemd-resolvedresolvectl query example.comView examples
Inspect resolver statisticsresolvectl statisticsView examples
Bypass the local cacheresolvectl --cache=no query example.comView examples
Flush resolved cachessudo resolvectl flush-cachesView examples
Request DNSSEC recordsdig example.com A +dnssec +multiView examples
Show per-link domainsresolvectl domainView examples
Set transient split DNSsudo resolvectl domain tun0 '~corp.example'View examples
Set a per-link DNS serversudo resolvectl dns tun0 192.0.2.53View examples
Revert transient link DNSsudo resolvectl revert tun0View examples

Networking and Connectivity · 17 commands

Linux Network Diagnostics Cheat Sheet

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UseSyntaxExamples
Show interface addressesip -brief address showView examples
Inspect link countersip -s link show dev eth0View examples
Show routesip route showView examples
Resolve an outbound routeip route get 1.1.1.1View examples
Inspect neighborsip neighbor showView examples
Send a bounded pingping -c 4 example.comView examples
Test IPv6 reachabilityping -6 -c 4 example.comView examples
Show listening TCP socketsss -lntView examples
Show established TCP socketsss -nt state establishedView examples
Include owning processessudo ss -lntpView examples
Use system name resolutiongetent ahosts example.comView examples
Query an A recorddig example.com AView examples
Show concise DNS answersdig +short example.com AAAAView examples
Fetch response headerscurl -I https://example.com/View examples
Print an HTTP statuscurl -sS -o /dev/null -w '%{http_code}\n' \ https://example.com/View examples
Bound connection timecurl --connect-timeout 5 https://example.com/View examples
Trace a requestcurl -v --connect-timeout 5 https://example.com/View examples

Networking and Connectivity · 14 commands

Linux nftables Firewall Cheat Sheet

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UseSyntaxExamples
List the rulesetsudo nft list rulesetView examples
Show rule handlessudo nft --handle list rulesetView examples
Back up active rulessudo nft list ruleset > ./nftables.backupView examples
Validate a filesudo nft --check --file ./nftables.confView examples
Load a batchsudo nft --file ./nftables.confView examples
Create an inet tablesudo nft add table inet filterView examples
Create an input base chainsudo nft \ 'add chain inet filter input { type filter hook input priority filter; policy drop; }'View examples
Allow established trafficsudo nft add rule inet filter input ct state \ established,related acceptView examples
Allow loopbacksudo nft add rule inet filter input iifname lo acceptView examples
Allow TCP servicesudo nft add rule inet filter input tcp dport 22 ct \ state new accept comment 'management SSH'View examples
Create an address setsudo nft \ 'add set inet filter admins { type ipv4_addr; flags interval; }'View examples
Count rule matchessudo nft add rule inet filter input tcp dport 443 \ counter acceptView examples
Monitor tracessudo nft monitor traceView examples
Monitor ruleset eventssudo nft monitor rulesetView examples

Networking and Connectivity · 20 commands

NetworkManager Wi-Fi and Connections Cheat Sheet

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UseSyntaxExamples
Show overall statusnmcli general statusView examples
List devicesnmcli device statusView examples
List active profilesnmcli connection show --activeView examples
Inspect a profilenmcli -f connection,ipv4,ipv6 connection show id \ 'Office Wi-Fi'View examples
List access pointsnmcli -f IN-USE,SSID,BSSID,CHAN,RATE,SIGNAL,SECURITY \ device wifi list ifname wlp2s0View examples
Request a rescannmcli device wifi rescan ifname wlp2s0View examples
Connect with a promptnmcli --ask device wifi connect 'Office Wi-Fi' ifname \ wlp2s0 name 'Office Wi-Fi'View examples
Activate using a secrets filenmcli connection up id 'Office Wi-Fi' ifname wlp2s0 \ passwd-file /run/user/1000/nm-secretsView examples
Activate by UUIDnmcli connection up uuid \ 3f4f1df0-a596-4ca4-94be-31d6c0674c5e ifname wlp2s0View examples
Deactivate a profilenmcli connection down uuid \ 3f4f1df0-a596-4ca4-94be-31d6c0674c5eView examples
Set autoconnect prioritysudo nmcli connection modify id 'Office Wi-Fi' \ connection.autoconnect yes \ connection.autoconnect-priority 20View examples
Configure static IPv4sudo nmcli connection modify id 'Office LAN' ipv4.method \ manual ipv4.addresses 192.0.2.20/24 ipv4.gateway \ 192.0.2.1View examples
Set profile DNSsudo nmcli connection modify id 'Office LAN' \ ipv4.ignore-auto-dns yes ipv4.dns \ '192.0.2.53 192.0.2.54'View examples
Add a profile routesudo nmcli connection modify id 'Office LAN' \ +ipv4.routes '198.51.100.0/24 192.0.2.1, 50'View examples
Reload profilessudo nmcli connection reloadView examples
Reapply compatible settingssudo nmcli device reapply wlp2s0View examples
Run under a checkpointsudo nmcli device checkpoint --timeout 60 wlp2s0 -- \ nmcli connection up id 'Office Wi-Fi'View examples
Monitor changesnmcli monitorView examples
Read service logsjournalctl -u NetworkManager.service --since today \ --no-pagerView examples
Show nmcli versionnmcli --versionView examples

Networking and Connectivity · 22 commands

WireGuard VPN Cheat Sheet

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UseSyntaxExamples
Show all interfacessudo wg showView examples
Show runtime configurationsudo wg showconf wg0View examples
List WireGuard interfaceswg show interfacesView examples
Generate a private keyumask 077; wg genkey > privatekeyView examples
Derive a public keywg pubkey < privatekey > publickeyView examples
Generate a preshared keyumask 077; wg genpsk > presharedkeyView examples
Create an interfacesudo ip link add dev wg0 type wireguardView examples
Load configurationsudo wg setconf wg0 /etc/wireguard/wg0.confView examples
Assign a tunnel addresssudo ip address add 10.20.0.1/24 dev wg0View examples
Bring the link upsudo ip link set up dev wg0View examples
Start with wg-quicksudo wg-quick up wg0View examples
Stop with wg-quicksudo wg-quick down wg0View examples
Save runtime statesudo wg-quick save wg0View examples
Synchronize peer configsudo wg syncconf wg0 /run/wireguard/wg0.stripped.confView examples
Strip wg-quick fieldssudo wg-quick strip wg0View examples
Check route selectionip route get 10.20.0.2View examples
Show handshake epochssudo wg show wg0 latest-handshakesView examples
Show transfer counterssudo wg show wg0 transferView examples
Show learned endpointssudo wg show wg0 endpointsView examples
Update one peersudo wg set wg0 peer PUBLIC_KEY allowed-ips 10.20.0.2/32 \ endpoint vpn.example.net:51820View examples
Remove a peersudo wg set wg0 peer PUBLIC_KEY removeView examples
Show tools versionwg --versionView examples

Containers, Virtualization, and Performance · 16 commands

cgroup v2 Resource Control Cheat Sheet

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UseSyntaxExamples
Confirm cgroup v2stat -fc %T /sys/fs/cgroupView examples
Show current cgroupcat /proc/self/cgroupView examples
List available controllerscat /sys/fs/cgroup/cgroup.controllersView examples
Find unit cgroupsystemctl show api.service -p ControlGroupView examples
Run a limited scopesystemd-run --user --scope -p MemoryHigh=768M -p \ MemoryMax=1G -p CPUQuota=150% make -j4View examples
Apply memory throttleMemoryHigh=768MView examples
Apply hard memory limitMemoryMax=1GView examples
Read memory eventscat \ /sys/fs/cgroup/system.slice/api.service/memory.eventsView examples
Set relative CPU weightCPUWeight=200View examples
Cap CPU bandwidthCPUQuota=150%View examples
Set relative I/O weightIOWeight=200View examples
Limit tasksTasksMax=512View examples
List member processescat /sys/fs/cgroup/system.slice/api.service/cgroup.procsView examples
Enable child controllersprintf '%s\n' '+cpu +memory +pids' | sudo tee \ /sys/fs/cgroup/ops.slice/cgroup.subtree_controlView examples
Watch cgroup usagesystemd-cgtop --depth=3View examples
Read CPU pressurecat /sys/fs/cgroup/system.slice/api.service/cpu.pressureView examples

Containers, Virtualization, and Performance · 20 commands

Containers with Podman Cheat Sheet

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UseSyntaxExamples
Inspect engine and hostpodman info --format jsonView examples
Check subordinate ID rangesgetent subuid "$USER"; getent subgid "$USER"View examples
Pull an immutable imagepodman pull docker.io/library/nginx@sha256:DIGESTView examples
Run with a read-only rootpodman run --read-only --cap-drop=all \ --security-opt=no-new-privileges --tmpfs \ /tmp:rw,noexec,nosuid,nodev IMAGEView examples
Publish only on loopbackpodman run -p 127.0.0.1:8080:8080 IMAGEView examples
Bound memory and CPUspodman run --memory=512m --cpus=1.5 --pids-limit=256 \ IMAGEView examples
Create an application networkpodman network create app-netView examples
Create a named volumepodman volume create app-dataView examples
Relabel a private bind mountpodman run -v /srv/app/config:/app/config:ro,Z IMAGEView examples
Create a secret from standard inputprintf '%s' "$DB_PASSWORD" | podman secret create db_password -View examples
Mount a runtime secretpodman run --secret db_password,type=mount IMAGEView examples
Provide a build secretpodman build --secret id=npmrc,src="$HOME/.npmrc" -t \ localhost/app:build .View examples
Regenerate rootless unitssystemctl --user daemon-reloadView examples
Verify generated servicesystemd-analyze --user --generators=true verify \ app.serviceView examples
Inspect health statepodman inspect --format '{{.State.Health.Status}}' appView examples
Stream lifecycle eventspodman events --filter container=appView examples
Preview automatic updatespodman auto-update --dry-runView examples
Export a named volumepodman volume export app-data --output app-data.tarView examples
Archive an OCI imagepodman save --format oci-archive --output app-image.tar \ IMAGEView examples
Run Podman diagnosticspodman system check --quickView examples

Containers, Virtualization, and Performance · 15 commands

Linux Namespaces, unshare, and nsenter Cheat Sheet

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UseSyntaxExamples
List namespace objectslsnsView examples
Inspect one processlsns --task 4242View examples
Read namespace linksreadlink \ /proc/4242/ns/{user,mnt,pid,net,uts,ipc,cgroup,time}View examples
Compare namespace identitystat -Lc '%i' /proc/self/ns/net /proc/4242/ns/netView examples
Map current user to rootunshare --user --map-root-user --mount /bin/shView examples
Preserve numeric identityunshare --user --map-current-user idView examples
Create private mount viewunshare --user --map-root-user --mount --propagation \ private /bin/shView examples
Create PID namespaceunshare --user --map-root-user --pid --fork --mount-proc \ --kill-child /bin/shView examples
Isolate hostnameunshare --user --map-root-user --uts sh -c \ 'hostname lab && hostname'View examples
Create network namespacesudo unshare --net --fork ip link showView examples
Enter mount namespacesudo nsenter --target 4242 --mount -- findmntView examples
Enter network namespacesudo nsenter --target 4242 --net -- ip address showView examples
Enter target environmentsudo nsenter --target 4242 --all --root --wd -- /bin/shView examples
Persist UTS namespacesudo unshare --uts=/run/namespaces/app-uts hostname \ app-sandboxView examples
Release namespace handlesudo umount /run/namespaces/app-utsView examples

Containers, Virtualization, and Performance · 17 commands

Linux Performance Observability Cheat Sheet

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UseSyntaxExamples
Show load and uptimeuptimeView examples
Sample system activityvmstat 1 5View examples
Count available CPUsnprocView examples
Sample every CPUmpstat -P ALL 1 5View examples
Sample process CPUpidstat -u -p ALL 1 5View examples
Summarize memoryfree --humanView examples
Sample process memorypidstat -r -p ALL 1 5View examples
Read memory pressurecat /proc/pressure/memoryView examples
Sample extended device I/Oiostat -xz 1 5View examples
Sample process I/Opidstat -d -p ALL 1 5View examples
Read I/O pressurecat /proc/pressure/ioView examples
Read historical CPU datasar -u -f /var/log/sa/sa12View examples
Sample queue and loadsar -q ALL 1 5View examples
Measure a bounded commandperf stat -- openssl speed -seconds 5 sha256View examples
List available eventsperf listView examples
Sample one processsudo perf record --call-graph dwarf --pid 4242 -- sleep \ 30View examples
Read a profileperf report --stdio --input=perf.dataView examples

Containers, Virtualization, and Performance · 23 commands

perf, ftrace, and eBPF Observability Cheat Sheet

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UseSyntaxExamples
Measure one commandperf stat -- sleep 10View examples
Measure one processsudo perf stat --pid 1234 -- sleep 10View examples
List available perf eventsperf listView examples
List dynamic probessudo perf probe --listView examples
Record process call graphssudo perf record --call-graph dwarf --pid 1234 -- sleep \ 30View examples
Open a perf reportperf report --stdio --input perf.dataView examples
Profile one process livesudo perf top --pid 1234View examples
Trace one process syscallssudo timeout 10 perf trace --pid 1234View examples
Locate tracefsfindmnt -t tracefs -o TARGET,SOURCE,OPTIONSView examples
List ftrace tracerssudo cat /sys/kernel/tracing/available_tracersView examples
List tracepointssudo cat /sys/kernel/tracing/available_eventsView examples
Stream ftrace outputsudo cat /sys/kernel/tracing/trace_pipeView examples
Clear the trace buffersudo sh -c ': > /sys/kernel/tracing/trace'View examples
Disable global tracingsudo sh -c 'echo 0 > /sys/kernel/tracing/tracing_on'View examples
Probe BPF supportsudo bpftool feature probe kernelView examples
List loaded BPF programssudo bpftool prog showView examples
List BPF mapssudo bpftool map showView examples
List matching probessudo bpftrace --list 'tracepoint:sched:sched_process_*'View examples
Count process executionssudo timeout 30 bpftrace -e \ 'tracepoint:sched:sched_process_exec { @[comm] = count(); }'View examples
Show bpftrace environmentbpftrace --infoView examples
Check kernel lockdowncat /sys/kernel/security/lockdownView examples
Read perf restrictionssysctl kernel.perf_event_paranoid kernel.kptr_restrictView examples
Inspect profile artifactstat --format='%a %U:%G %s %n' perf.dataView examples

Containers, Virtualization, and Performance · 24 commands

QEMU, KVM, and libvirt Cheat Sheet

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UseSyntaxExamples
Inspect CPU virtualization flagslscpu | grep -E 'Virtualization|Hypervisor vendor'View examples
Validate the KVM hostsudo virt-host-validate qemuView examples
Show the active libvirt URIvirsh --connect qemu:///system uriView examples
Inspect domain capabilitiesvirsh --connect qemu:///system domcapabilitiesView examples
List every domainvirsh --connect qemu:///system list --allView examples
Inspect domain statevirsh --connect qemu:///system dominfo prod-vmView examples
Export inactive domain XMLvirsh --connect qemu:///system dumpxml --inactive \ prod-vmView examples
Request a graceful shutdownvirsh --connect qemu:///system shutdown prod-vmView examples
Create a qcow2 diskqemu-img create -f qcow2 ./prod-vm.qcow2 80GView examples
Inspect image metadataqemu-img info --backing-chain \ /var/lib/libvirt/images/prod-vm.qcow2View examples
List storage-pool volumesvirsh --connect qemu:///system vol-list default \ --detailsView examples
Map guest disks to sourcesvirsh --connect qemu:///system domblklist prod-vm \ --detailsView examples
Query guest filesystemsvirsh --connect qemu:///system domfsinfo prod-vmView examples
Inspect vCPU placementvirsh --connect qemu:///system vcpuinfo prod-vmView examples
List domain interfacesvirsh --connect qemu:///system domiflist prod-vmView examples
List DHCP leasesvirsh --connect qemu:///system net-dhcp-leases defaultView examples
Inspect network configurationvirsh --connect qemu:///system net-dumpxml defaultView examples
List snapshot ancestryvirsh --connect qemu:///system snapshot-list prod-vm \ --treeView examples
Start a defined live backupvirsh --connect qemu:///system backup-begin prod-vm \ --backupxml /etc/libvirt/backup/prod-vm.xmlView examples
Inspect a block jobvirsh --connect qemu:///system blockjob prod-vm vda \ --info --bytesView examples
Check an offline imageqemu-img check /srv/backups/prod-vm/prod-vm.qcow2View examples
Check destination CPU compatibilityvirsh --connect qemu+ssh://hv2/system \ hypervisor-cpu-compare prod-vm.migratable.xml --error \ --validateView examples
Inspect domain security labelsvirsh --connect qemu:///system dominfo prod-vm | grep -E '^Security'View examples
Read the QEMU domain logsudo journalctl -u 'virtqemud*' --since -30minView examples
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