If you want to edit files within default (not host path) volumes for a TrueNAS scale app, you need to know where to find the volume mounted on disk.

This process will only work if a pod currently exists (the app is not stopped/scaled to 0 replicas) since the volume is only mounted by kubelet then.
If that is not the case (you want to edit files offline), you can just mount the underlying ZFS volume yourself to make the changes. See the TrueCharts documentation for that.

Get PVCs in namespace

# k3s kubectl -n ix-appdaemon get pvc

NAME             STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS                 AGE
appdaemon-conf   Bound    pvc-e726219d-e2d5-4e77-9e20-02408203587d   256Gi      RWO            ix-storage-class-appdaemon   125d

You can see that appdaemon-conf is the underlying PV: pvc-e726219d-e2d5-4e77-9e20-02408203587.

Get PVC ZFS location

If we then describe the PV:

# k3s kubectl describe pv pvc-e726219d-e2d5-4e77-9e20-02408203587d

Name:              pvc-e726219d-e2d5-4e77-9e20-02408203587d
Labels:            <none>
Annotations:       pv.kubernetes.io/provisioned-by: zfs.csi.openebs.io
Finalizers:        [kubernetes.io/pv-protection]
StorageClass:      ix-storage-class-appdaemon
Status:            Bound
Claim:             ix-appdaemon/appdaemon-conf
Reclaim Policy:    Retain
Access Modes:      RWO
VolumeMode:        Filesystem
Capacity:          256Gi
Node Affinity:
  Required Terms:
    Term 0:        openebs.io/nodeid in [ix-truenas]
Message:
Source:
    Type:              CSI (a Container Storage Interface (CSI) volume source)
    Driver:            zfs.csi.openebs.io
    FSType:            zfs
    VolumeHandle:      pvc-e726219d-e2d5-4e77-9e20-02408203587d
    ReadOnly:          false
    VolumeAttributes:      openebs.io/cas-type=localpv-zfs
                           openebs.io/poolname=Vol1/ix-applications/releases/appdaemon/volumes
                           storage.kubernetes.io/csiProvisionerIdentity=1693657662253-8081-zfs.csi.openebs.io
Events:                <none>

We can see that it’s a ZFS dataset located in Vol1/ix-applications/releases/appdaemon/volumes.

Find mount point

If we check zfs list for our PV:

# zfs list | grep pvc-e726219d-e2d5-4e77-9e20-02408203587d

Vol1/ix-applications/releases/appdaemon/volumes/pvc-e726219d-e2d5-4e77-9e20-02408203587d         1007K   256G   240K  legacy

We can see the ZFS volume path, and that it is configured with mountpoint set to legacy.

So we need to check the mount command:

# mount | grep pvc-e726219d-e2d5-4e77-9e20-02408203587d

/var/lib/kubelet/pods/e45037b1-08c8-4e74-85d0-fc00b63c7ba5/volumes/kubernetes.io~csi/pvc-e726219d-e2d5-4e77-9e20-02408203587d/mount

And there we have the final path where the volume is currently mounted and can cd to it.

TL;DR

The above in short:

# k3s kubectl -n ix-<appname> get pvc

NAME             STATUS   VOLUME     CAPACITY   ACCESS MODES   STORAGECLASS                 AGE
<claimname>      Bound    <pvname>   256Gi      RWO            ix-storage-class-<appname>   125d

# mount | grep <pvname>