{"record":{"id":"25e831d6a00e7442","repo":"hashicorp/nomad","slug":"failed-to-open-current-namespace-v","errorCode":null,"errorMessage":"Failed to open current namespace: %v","messagePattern":"Failed to open current namespace: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"client/lib/nsutil/ns_linux.go","lineNumber":207,"sourceCode":"\t\t}\n\t\tdefer func() {\n\t\t\terr := threadNS.Set() // switch back\n\t\t\tif err == nil {\n\t\t\t\t// Unlock the current thread only when we successfully switched back\n\t\t\t\t// to the original namespace; otherwise leave the thread locked which\n\t\t\t\t// will force the runtime to scrap the current thread, that is maybe\n\t\t\t\t// not as optimal but at least always safe to do.\n\t\t\t\truntime.UnlockOSThread()\n\t\t\t}\n\t\t}()\n\n\t\treturn toRun(hostNS)\n\t}\n\n\t// save a handle to current network namespace\n\thostNS, err := GetCurrentNS()\n\tif err != nil {\n\t\treturn fmt.Errorf(\"Failed to open current namespace: %v\", err)\n\t}\n\tdefer hostNS.Close()\n\n\tvar wg sync.WaitGroup\n\twg.Add(1)\n\n\t// Start the callback in a new green thread so that if we later fail\n\t// to switch the namespace back to the original one, we can safely\n\t// leave the thread locked to die without a risk of the current thread\n\t// left lingering with incorrect namespace.\n\tvar innerError error\n\tgo func() {\n\t\tdefer wg.Done()\n\t\truntime.LockOSThread()\n\t\tinnerError = containedCall(hostNS)\n\t}()\n\twg.Wait()\n","sourceCodeStart":189,"sourceCodeEnd":225,"githubUrl":"https://github.com/hashicorp/nomad/blob/482b49bf1aec006f089bcfc7e632d8f6ac303e5e/client/lib/nsutil/ns_linux.go#L189-L225","documentation":"netNS.Do() first saves a handle to the caller's current network namespace via GetCurrentNS() so it can be restored after running the callback in the target namespace. This error wraps a failure to open that initial handle, aborting the entire Do() operation.","triggerScenarios":"Calling Do() (e.g. via withNetworkIsolation) when GetCurrentNS() fails: /proc/self/ns/net cannot be opened due to missing /proc, fd exhaustion, or insufficient permissions.","commonSituations":"Client running in a container without /proc mounted; process at its open-file limit; hardened environments where namespace files are unreadable; very early startup before /proc is available.","solutions":["Ensure /proc is mounted and /proc/self/ns/net is readable by the process","Raise the fd soft limit (ulimit -n) if EMFILE","Run with privileges allowing namespace file access (CAP_SYS_ADMIN / DAC override as needed)","Check the wrapped GetCurrentNS error for the exact errno","Pre-open/validate the netns path before invoking Do()"],"exampleFix":"// before\nhostNS, err := GetCurrentNS() // fails: no /proc\nif err != nil {\n    return fmt.Errorf(\"Failed to open current namespace: %v\", err)\n}\n// after\nif _, err := os.Stat(\"/proc/self/ns/net\"); err != nil {\n    return fmt.Errorf(\"/proc/self/ns/net unavailable (mount /proc): %w\", err)\n}\nhostNS, err := GetCurrentNS()\nif err != nil {\n    return fmt.Errorf(\"Failed to open current namespace: %w\", err)\n}","handlingStrategy":"validation","validationCode":"func ensureCurrentNsReadable() error {\n    f, err := os.Open(\"/proc/self/ns/net\")\n    if err != nil {\n        return fmt.Errorf(\"cannot open current netns (mount /proc?): %w\", err)\n    }\n    return f.Close()\n}","typeGuard":null,"tryCatchPattern":"if err := withNetworkIsolation(work); err != nil {\n    if strings.Contains(err.Error(), \"Failed to open current namespace\") {\n        return fmt.Errorf(\"netns isolation unavailable; check /proc and privileges: %w\", err)\n    }\n    return err\n}","preventionTips":["Ensure /proc is mounted before namespace isolation features run","Keep fd usage below RLIMIT_NOFILE","Grant capabilities required to open namespace files","Fail fast at startup by probing /proc/self/ns/net early"],"tags":["linux","network-namespace","procfs","initialization"],"backgroundTag":"netns-open-failed","analyzedSha":"482b49bf1aec006f089bcfc7e632d8f6ac303e5e","analyzedAt":"2026-09-04T07:54:14.808Z","contentChangedAt":"2026-09-04T07:54:14.808Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}