简单总结

使用containerd仓库Makefile构建的containerd时添加了netgo的编译参数
导致了contaienrd只会在启动时候读取一次/etc/hosts加载到内存中,后续/etc/hosts的修改对于containerd不会生效
这是go build的行为

解决方案

使用netcgo重新编译containerd

GODEBUG=netdns=cgo或者build tags netcgo

修改完/etc/hosts后重启containerd

相关源码

net/lookup_unix.go中

dns解析
func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
    查看order和conf
    order, conf := systemConf().hostLookupOrder(r, name)
    if order == hostLookupCgo {
        cgo dns解析
        if cname, err, ok := cgoLookupCNAME(ctx, name); ok {
            return cname, err
        }
    }
    go dns解析
    return r.goLookupCNAME(ctx, name, order, conf)
}

net/conf.go

dns解析配置
func systemConf() *conf {
    初始化confVal
    confOnce.Do(initConfVal)
    return confVal
}

初始化confVal
func initConfVal() {
    dnsMode, debugLevel := goDebugNetDNS()
    GODEBUG=netdns=go或者build tags netgo
    confVal.netGo = netGoBuildTag || dnsMode == "go"
    GODEBUG=netdns=cgo或者build tags netcgo
    confVal.netCgo = netCgoBuildTag || dnsMode == "cgo"
    ...
}

查询order和conf
func (c *conf) hostLookupOrder(r *Resolver, hostname string) (ret hostLookupOrder, dnsConf *dnsConfig) {
    ...
    查询order和conf
    return c.lookupOrder(r, hostname)
}

查看order和conf
func (c *conf) lookupOrder(r *Resolver, hostname string) (ret hostLookupOrder, dnsConf *dnsConfig) {
    ...
    var fallbackOrder hostLookupOrder

    var canUseCgo bool
    if c.mustUseGoResolver(r) {
        fallbackOrder = hostLookupFilesDNS
        canUseCgo = false
    } else if c.netCgo {
        return hostLookupCgo, nil
    } else if c.preferCgo {
        return hostLookupCgo, nil
    } else {
        if bytealg.IndexByteString(hostname, '\\') != -1 || bytealg.IndexByteString(hostname, '%') != -1 {
            return hostLookupCgo, nil
        }

        fallbackOrder = hostLookupCgo
        canUseCgo = true
    }
    ...
}