hashicorp/nomad · error

unable to convert user's group to uint32 %s: %v

Error message

unable to convert user's group to uint32 %s: %v

What it means

Each group id string returned by u.GroupIds() is parsed with strconv.ParseUint(gid, 10, 32) to build the uint32 list used in the syscall credential. If a GID string is non-numeric or exceeds 32 bits, the loop returns this wrapped parse error.

Source

Thrown at drivers/shared/executor/executor_unix.go:77

// setCmdUser takes a user id as a string and looks up the user, and sets the command
// to execute as that user.
func setCmdUser(cmd *exec.Cmd, userid string) error {
	u, err := users.Lookup(userid)
	if err != nil {
		return fmt.Errorf("failed to identify user %v: %v", userid, err)
	}

	// Get the groups the user is a part of
	gidStrings, err := u.GroupIds()
	if err != nil {
		return fmt.Errorf("unable to lookup user's group membership: %v", err)
	}

	gids := make([]uint32, len(gidStrings))
	for _, gidString := range gidStrings {
		u, err := strconv.ParseUint(gidString, 10, 32)
		if err != nil {
			return fmt.Errorf("unable to convert user's group to uint32 %s: %v", gidString, err)
		}

		gids = append(gids, uint32(u))
	}

	// Convert the uid and gid
	uid, err := strconv.ParseUint(u.Uid, 10, 32)
	if err != nil {
		return fmt.Errorf("unable to convert userid to uint32: %w", err)
	}
	gid, err := strconv.ParseUint(u.Gid, 10, 32)
	if err != nil {
		return fmt.Errorf("unable to convert groupid to uint32: %s", err)
	}

	// Set the command to run as that user and group.
	if cmd.SysProcAttr == nil {
		cmd.SysProcAttr = &syscall.SysProcAttr{}

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Run 'id <username>' and inspect each returned group for non-numeric or >4294967295 values.
2. Fix the offending /etc/group entry or the LDAP/NSS source producing invalid GIDs.
3. Remove the user from groups with invalid GIDs until the source is corrected.

Example fix

// before (/etc/group)
broken-group:x:4294967296:appuser
// after
broken-group:x:4294967295:appuser

// Go: sanity-check that every gid for the task user parses as uint32
for _, g := range gidStrings {
    if _, err := strconv.ParseUint(g, 10, 32); err != nil {
        return fmt.Errorf("invalid gid %q for task user", g)
    }
}

func isUint32(s string) bool {
    _, err := strconv.ParseUint(s, 10, 32)
    return err == nil
}

if err := exec.SetUser(cmd, userid); err != nil {
    if strings.Contains(err.Error(), "convert user's group to uint32") {
        // group data corrupt: fail fast, don't retry
    }
    return err
}

When it happens

Trigger: GroupIds() returns a malformed or out-of-range GID (e.g. negative or >4294967295 value coming from an NSS/LDAP backend, or non-numeric garbage in the group database).

Common situations: LDAP directory exposing SIDs or non-numeric group identifiers; corrupted /etc/group entries; 64-bit GIDs on unusual NSS sources.

Related errors

• unable to convert groupid to uint32: %s
• unable to convert userid to uint32: %w
• failed to identify user %v: %v
• unable to lookup user's group membership: %v
• error creating fifo: %w

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/e5951ae5ab60e5f4. Report an issue: GitHub.