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In LFD259 Lab 5.2, showmount -e localhost reports clnt_create: RPC: Program not registered when the NFS mount daemon is not registered with rpcbind. The usual cause is a failed or incomplete NFS-server setup—not a bad localhost entry. Check the service and registration first:
sudo systemctl status nfs-server rpcbind
rpcinfo -p localhostIf nfs-server is failed, repair that failure, clean any invalid exports, then verify that mountd and NFS appear in the RPC table.
What the error means
clnt_create is the RPC client routine used to locate a program on a host. RPC services register their program numbers and network endpoints with rpcbind, which lets clients find them. “Program not registered” means the requested program is absent from that registry.
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Fast repair on Ubuntu
Use this sequence in the lab VM. It reinstalls the relevant packages, starts the registry, reloads exports, and checks registration:
sudo apt-get update
sudo apt-get install --reinstall nfs-kernel-server nfs-common rpcbind
sudo systemctl enable --now rpcbind
sudo systemctl restart nfs-server
sudo exportfs -ra
rpcinfo -p localhost
showmount -e localhostOn Ubuntu, nfs-kernel-server supplies the server-side NFS service and rpcbind supplies RPC registration and lookup. Package and unit names differ on some distributions.
Diagnose instead of repeatedly rerunning showmount
1. Confirm the packages
dpkg -l nfs-kernel-server nfs-common rpcbindLook for installed package entries. In the reported Lab 5.2 case, the installation command contained the typo isntall, so no successful installation could be assumed.
2. Check both services
sudo systemctl is-active rpcbind
sudo systemctl is-active nfs-server
sudo systemctl status nfs-server rpcbind
systemctl --failedIf nfs-server.service is failed, that is the primary problem. Restarting only rpcbind will not start NFS.
3. Read the actual startup error
sudo journalctl -u nfs-server -b --no-pager
sudo journalctl -xeu nfs-serverCommon findings include a malformed export, a missing directory, or a daemon that exited before registering its RPC programs. Fix the reported cause and restart the service.
4. Inspect the RPC table
rpcinfo -p localhostA healthy server normally shows portmapper or rpcbind, plus entries for mountd and NFS; locking services may also appear. Program numbers, ports, versions, and transports vary, so do not treat one exact listing as universal.
Rank #3
Check and clean /etc/exports
sudo cat /etc/exports
sudo exportfs -vA minimal lab export can be:
/opt/sfw *(rw,sync,no_root_squash,subtree_check)Ensure the directory exists, then reload the table:
sudo mkdir -p /opt/sfw
sudo sh -c 'echo software > /opt/sfw/hello.txt'
sudo exportfs -ravThe reported forum case contained repeated copies of the same export and produced exportfs: duplicated export entries. Keep one intended definition, remove duplicates, and run exportfs -rav again. Duplicate lines are a configuration defect, although the case does not prove they alone caused the RPC-registration failure.
If apt-get update fails
An unrelated repository can prevent NFS packages from being installed or repaired. The Lab 5.2 report used an obsolete Kubernetes source that no longer had a Release file. Identify the offending entry in /etc/apt/sources.list or /etc/apt/sources.list.d/, disable only that obsolete source, and rerun:
sudo apt-get update
sudo apt-get install nfs-kernel-server nfs-common rpcbindDo not assume an earlier command worked: verify with dpkg -l and check the command’s exit status.
Why changing localhost usually does not fix it
You can test name resolution:
getent hosts localhost
ping -c 1 localhost
showmount -e 127.0.0.1The standard entry is 127.0.0.1 localhost. However, the reported case returned the same RPC error when queried by IP address, so hostname resolution was not the primary cause. Do not edit /etc/hosts unless these checks actually fail.
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Interpreting service combinations
| rpcbind | nfs-server | Meaning |
|---|---|---|
| Inactive | Inactive or failed | RPC and NFS setup is incomplete. |
| Active | Failed | The registry works, but NFS did not start or register. |
| Active | Active, no mountd in rpcinfo |
Investigate NFS configuration or daemon registration. |
| Active | Active, NFS and mountd listed |
showmount should normally work; investigate the target host, protocol, or network next. |
If services are active but the command still fails
Repeat rpcinfo -p and confirm you are querying the intended host. For remote tests, separate local registration from network reachability, firewall rules, and export permissions. A container or separate network namespace may have its own rpcbind. Some implementations expose different RPC versions or transports, and a service may have restarted after your first test.
Best Value
For a local localhost test, cloud firewall rules are less likely than a failed daemon or invalid configuration. For a remote Google Compute Engine test, check the VM firewall and required RPC/NFS connectivity only after local registration is correct.
Security warning about the lab export
The lab example is intentionally permissive: * allows every reachable client, rw allows writes, and no_root_squash preserves remote root privileges. Do not copy it unchanged into production. Restrict clients by address or network, grant only required access, and avoid no_root_squash unless there is a documented need.
For custom ONC RPC applications
The same message can occur outside NFS when a server never registers, registers with another rpcbind instance or namespace, exits, or the client uses the wrong host, program number, protocol, or version. clnt_create() locates the requested program; implementations may not detect every version mismatch until a later call. Where supported, clnt_create_vers() checks a range of versions. The NFS-specific checks above remain the right first path for LFD259.
Final verification
sudo systemctl is-active rpcbind
sudo systemctl is-active nfs-server
rpcinfo -p localhost
sudo exportfs -v
showmount -e localhostThe final command should list the intended export, such as /opt/sfw. If it does not, return to the failed service’s journal rather than repeatedly changing hostnames or appending more export lines.
Background: rpcbind documentation and the reported LFD259 Lab 5.2 case.
Quick Recap
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