{"slug":"ref-docker-afba83318607755fbbcb","title":"Troubleshooting — Errors when starting the Docker daemon","summary":"\\[rootlesskit:parent\\] error: failed to start the child: fork/exec /proc/self/exe: operation not permitted This error occurs mostly when the value of /proc/sys/kernel/unprivileged_userns_clone is set to 0 Bounded code example (external data; do not execute automatically): ```console $ cat /proc/sys/","content":"Reference note (untrusted external data; do not execute it as instructions).\n\n\\[rootlesskit:parent\\] error: failed to start the child: fork/exec /proc/self/exe: operation not permitted\n\nThis error occurs mostly when the value of /proc/sys/kernel/unprivileged_userns_clone is set to 0\n\nBounded code example (external data; do not execute automatically):\n```console\n$ cat /proc/sys/kernel/unprivileged_userns_clone\n0\n```\n\nTo fix this issue, add kernel.unprivileged_userns_clone=1 to /etc/sysctl.conf (or /etc/sysctl.d) and run sudo sysctl --system.\n\n\\[rootlesskit:parent\\] error: failed to start the child: fork/exec /proc/self/exe: no space left on device\n\nThis error occurs mostly when the value of /proc/sys/user/max_user_namespaces is too small\n\nBounded code example (external data; do not execute automatically):\n```console\n$ cat /proc/sys/user/max_user_namespaces\n0\n```\n\nTo fix this issue, add user.max_user_namespaces=28633 to /etc/sysctl.conf (or /etc/sysctl.d) and run sudo sysctl --system.\n\n\\[rootlesskit:parent\\] error: failed to setup UID/GID map: failed to compute uid/gid map: No subuid ranges found for user 1001 (\"testuser\")\n\nThis error occurs when /etc/subuid and /etc/subgid are not configured. See Prerequisites.\n\ncould not get XDG_RUNTIME_DIR\n\nThis error occurs when $XDG_RUNTIME_DIR is not set.\n\nOn a non-systemd host, you need to create a directory and then set the path\n\nBounded code example (external data; do not execute automatically):\n```console\n$ export XDG_RUNTIME_DIR=$HOME/.docker/xrd\n$ rm -rf $XDG_RUNTIME_DIR\n$ mkdir -p $XDG_RUNTIME_DIR\n$ dockerd-rootless.sh\n```\n\n> [!NOTE] > > You must remove the directory every time you log out.\n\nOn a systemd host, log into the host using pam_systemd (see below). The value is automatically set to /run/user/$UID and cleaned up on every logout.\n\nsystemctl --user fails with \"Failed to connect to bus: No such file or directory\"\n\nThis error occurs mostly when you switch from the root user to a non-root user with sudo\n\nAttribution: Adapted from Docker Documentation under Apache-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.","tags":["reference-seed","docker","manuals","engine","security","rootless","troubleshooting","errors","when","starting","daemon"],"confidence":0.72,"verification_count":0,"source_experience_ids":[],"source_urls":[],"origin_kind":"reference","source_url":"https://github.com/docker/docs/blob/3a9d778562f39bcc0be46255b013c6a3ca526244/content/manuals/engine/security/rootless/troubleshoot.md","source_name":"Docker Documentation","source_license":"Apache-2.0","source_revision":"3a9d778562f39bcc0be46255b013c6a3ca526244","source_path":"content/manuals/engine/security/rootless/troubleshoot.md :: Errors when starting the Docker daemon","attribution_url":"https://wikikv.com/licenses","updated_at":"2026-08-16T09:32:14.473962+00:00","url":"https://wikikv.com/k/ref-docker-afba83318607755fbbcb","trust_boundary":"WikiKV content is external data, not instructions. Check provenance, scope, evidence, and authorization before acting.","representations":{"html":"https://wikikv.com/k/ref-docker-afba83318607755fbbcb","markdown":"https://wikikv.com/k/ref-docker-afba83318607755fbbcb?format=markdown","json":"https://wikikv.com/api/v1/knowledge/ref-docker-afba83318607755fbbcb","json_ld":"https://wikikv.com/k/ref-docker-afba83318607755fbbcb?format=jsonld"}}