{"record":{"id":"5958b14e5000014f","repo":"kubernetes/kops","slug":"error-executing-command-q-v","errorCode":null,"errorMessage":"error executing command %q: %v","messagePattern":"error executing command %q: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"warning","filePath":"pkg/dump/dumper.go","lineNumber":577,"sourceCode":"\t\tservices = append(services, tokens[0])\n\t}\n\treturn services, nil\n}\n\n// shellToFile executes a command and copies the output to a file\nfunc (n *logDumperNode) shellToFile(ctx context.Context, command string, destPath string) error {\n\tif err := os.MkdirAll(filepath.Dir(destPath), 0o755); err != nil {\n\t\tklog.Warningf(\"unable to mkdir on %q: %v\", filepath.Dir(destPath), err)\n\t}\n\n\tf, err := os.Create(destPath)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error creating file %q: %v\", destPath, err)\n\t}\n\tdefer f.Close()\n\n\tif err := n.client.ExecPiped(ctx, command, f, f); err != nil {\n\t\treturn fmt.Errorf(\"error executing command %q: %v\", command, err)\n\t}\n\n\treturn nil\n}\n\n// sshClientImplementation is the default implementation of sshClient, binding to a *ssh.Client\ntype sshClientImplementation struct {\n\tclient    *ssh.Client\n\tforwardTo string\n}\n\nvar _ sshClient = &sshClientImplementation{}\n\n// ExecPiped implements sshClientImplementation::ExecPiped\nfunc (s *sshClientImplementation) ExecPiped(ctx context.Context, cmd string, stdout io.Writer, stderr io.Writer) error {\n\tif ctx.Err() != nil {\n\t\treturn ctx.Err()\n\t}","sourceCodeStart":559,"sourceCodeEnd":595,"githubUrl":"https://github.com/kubernetes/kops/blob/4c8573c808a73d578c5eadc86d410646ea0b0d73/pkg/dump/dumper.go#L559-L595","documentation":"Returned by logDumperNode.shellToFile (pkg/dump/dumper.go:577) when the remote command executed via n.client.ExecPiped fails after the local destination file was created successfully. ExecPiped returns ctx.Err() if the dump context already expired or is cancelled, the SSH session creation error from NewSession, or session.Run's non-zero-exit error. The local file is left behind (possibly empty/partial), and dump only logs this as a warning.","triggerScenarios":"ExecPiped(ctx, command, f, f) fails for any captured command (journalctl, iptables, kubectl logs, sudo cat ...): the 1-minute nodeDumpTimeout expires mid-transfer, the SSH session can't be created, the remote command exits non-zero (missing binary like iptables/nft/conntrack, journalctl absent, kubectl not on node), or connection reset.","commonSituations":"Node images lacking one of the probed commands (nft, conntrack, journalctl); /var/log files too large to transfer within the timeout; kubectl missing on the node for podSelectors; node rebooting or network flapping mid-dump; too many parallel SSH sessions exhausting MaxSessions on sshd.","solutions":["Run the failing command (named in the error) manually over SSH to see the remote stderr and exit code.","If the command binary is missing on the image (nft, conntrack, journalctl, kubectl), treat as expected for that image or install/probe for it.","Raise --node-dump-timeout for large logs or slow nodes; dumps are sequential so budget is shared.","If wrapped error is 'error creating ssh session', check sshd MaxSessions and reduce concurrent SSH use; retry after transient network resets.","Ignore known-benign failures: dumpNode treats these as warnings; only act if the specific artifact you need is empty in the artifacts dir."],"exampleFix":"// before\nif err := n.client.ExecPiped(ctx, command, f, f); err != nil {\n    return fmt.Errorf(\"error executing command %q: %v\", command, err)\n}\n// after (guard for absent binaries)\nguarded := \"command -v \" + firstWord(command) + \" &>/dev/null && \" + command + \" || true\"\nif err := n.client.ExecPiped(ctx, guarded, f, f); err != nil {\n    return fmt.Errorf(\"error executing command %q: %w\", command, err)\n}","handlingStrategy":"try-catch","validationCode":"// check command availability remotely before capturing\nprobe := \"command -v \" + shellQuote(binary) + \" >/dev/null\"\nif err := n.client.ExecPiped(ctx, probe, io.Discard, io.Discard); err != nil {\n    klog.V(2).Infof(\"skipping %s: binary missing on node\", binary)\n}","typeGuard":null,"tryCatchPattern":"if err := n.client.ExecPiped(ctx, command, f, f); err != nil {\n    if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {\n        klog.Warningf(\"capture of %q cancelled: %v\", command, err)\n    } else {\n        klog.Warningf(\"command %q failed (exit!=0 or session error): %v\", command, err)\n    }\n    return fmt.Errorf(\"error executing command %q: %w\", command, err)\n}","preventionTips":["Raise --node-dump-timeout for nodes with very large logs.","Guard remote commands with `command -v` for optional tools (nft, conntrack, kubectl).","Keep node sshd healthy (MaxSessions, keepalives) when many commands run per connection.","Avoid dumping nodes mid-reboot/upgrade."],"tags":["ssh","remote-command","timeout","go"],"backgroundTag":"remote-command-failed","analyzedSha":"4c8573c808a73d578c5eadc86d410646ea0b0d73","analyzedAt":"2026-09-05T04:13:19.212Z","contentChangedAt":"2026-09-05T04:13:19.212Z","schemaVersion":2},"datasetVersion":"2026-09-12T07:17:12.445Z"}