trace_open

The trace_open gadget emits events when files are opened.

Getting started

Running the gadget:

kubectl gadget

$ kubectl gadget run ghcr.io/inspektor-gadget/gadget/trace_open:latest [flags]

ig

$ sudo ig run ghcr.io/inspektor-gadget/gadget/trace_open:latest [flags]

Flags

--failed

Show only failed events

Default value: "false"

--pid

Show only events generated by processes with this pid

Default value: ""

--uid

Show only events generated by processes with this uid

Default value: ""

Guide

This example shows how to use this gadget.

First, we need to run an application that generates some events.

kubectl gadget

$ kubectl run --restart=Never --image=busybox mypod -- sh -c 'while /bin/true ; do whoami ; sleep 3 ; done'
pod/mypod created

ig

$ docker run --name test-trace-open -d busybox /bin/sh -c 'while /bin/true ; do whoami ; sleep 3 ; done'

Then, let's run the gadget:

kubectl gadget

Using the trace_open gadget, we can see which processes open what files. We can simply filter for the pod "mypod" and omit specifying the node, thus tracing on all nodes for a pod called "mypod":

$ kubectl gadget run trace_open:latest --podname mypod
K8S.NODE           K8S.NAMESPACE K8S.PODNAME   K8S.CONTAINE… COMM        PID     TID      FD FNAME                    MODE    ERROR
minikube-docker    default       mypod         mypod         true     511559  511559       0 /etc/ld.so.cache         ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/g… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/g… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/t… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/t… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/t… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/t… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/x… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/x… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/x… ------… ENOEN
minikube-docker    default       mypod         mypod         true     511559  511559       0 /lib/x86_64-linux-gnu/l… ------… ENOEN
...
minikube-docker    default       mypod         mypod         whoami   511560  511560       0 /lib/x86_64/libm.so.6    ------… ENOEN
minikube-docker    default       mypod         mypod         whoami   511560  511560       3 /lib/libm.so.6           ------…
minikube-docker    default       mypod         mypod         whoami   511560  511560       3 /lib/libresolv.so.2      ------…
minikube-docker    default       mypod         mypod         whoami   511560  511560       3 /lib/libc.so.6           ------…
minikube-docker    default       mypod         mypod         whoami   511560  511560       3 /etc/passwd              ------…
^C

Seems the whoami command opens "/etc/passwd" to map the user ID to a user name. We can stop the gadget by hitting Ctrl-C.

ig

$ sudo ig run trace_open:latest --containername test-trace-open
RUNTIME.CONTAINERNA… COMM                PID         TID         FD FNAME                    MODE       ERROR
test-trace-open      true             515458      515458          0 /etc/ld.so.cache         ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/g… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/g… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/t… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/t… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/t… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/t… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/x… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/x… ---------- ENOENT
test-trace-open      true             515458      515458          0 /lib/x86_64-linux-gnu/x… ---------- ENOENT
...
test-trace-open      whoami           515459      515459          0 /lib/tls/x86_64/libm.so… ---------- ENOENT
test-trace-open      whoami           515459      515459          0 /lib/tls/libm.so.6       ---------- ENOENT
test-trace-open      whoami           515459      515459          0 /lib/x86_64/x86_64/libm… ---------- ENOENT
test-trace-open      whoami           515459      515459          0 /lib/x86_64/libm.so.6    ---------- ENOENT
test-trace-open      whoami           515459      515459          0 /lib/x86_64/libm.so.6    ---------- ENOENT
test-trace-open      whoami           515459      515459          3 /lib/libm.so.6           ----------
test-trace-open      whoami           515459      515459          3 /lib/libresolv.so.2      ----------
test-trace-open      whoami           515459      515459          3 /lib/libc.so.6           ----------
test-trace-open      whoami           515459      515459          3 /etc/passwd              ----------
^C

Finally, clean the system:

kubectl gadget

$ kubectl delete pod mypod

ig

$ docker rm -f test-trace-open