One container runs both the node_exporter (host) and cadvisor (container) collectors. A second, tiny container proxies a read-only slice of the Docker API to it. The Alloy config is embedded inline via Compose configs:, so there is no config.alloy on disk. There is no .env.example either: the nine variables are exported before docker compose up.

Both containers have fixed names, container_name: alloy and alloy-dockerproxy, and dockerproxy publishes 127.0.0.1:2375 — Alloy runs with host networking, so it has no compose network to reach the proxy over.

What it collects

Source	Component	Notes
Host metrics	`prometheus.exporter.unix`	CPU, memory, load, disk I/O, filesystem, network, uname, boot time, systemd, vmstat, sockstat — the default collector set minus `ipvs/btrfs/infiniband/xfs/zfs`
Container metrics	`prometheus.exporter.cadvisor`	CPU, memory, fs usage/limit, network, `last_seen`
Container logs	`loki.source.docker`	All running containers, labeled `container`, `stream`, `instance`
Journal logs	`loki.source.journal`	systemd journal, labeled `unit`, `boot_id`, `transport`, `level`
File logs	`loki.source.file`	`/var/log/syslog`, `/var/log/messages`, `/var/log/*.log`
Remote config	`remotecfg`	Polls Grafana Fleet Management every 60s

Metric filtering copies the keep-lists from the upstream Grafana Cloud integrations verbatim (Linux Node, Docker). Logs are unfiltered.

Where rsyslog mirrors journald into /var/log/syslog — the Debian and Ubuntu default — the journal and file pipelines double-ship the same lines. Drop one source on those hosts; the file-based one is the redundant one on systemd-only stacks.

Environment

All nine are required; docker compose up fails fast if any is unset.

Variable	Purpose
`ALLOY_HOSTNAME`	Container hostname, and the Loki/Prometheus `instance` label
`REMOTECFG_URL`	Fleet Management endpoint
`REMOTECFG_ID`	Fleet Management agent id
`REMOTECFG_USER`	Fleet Management user id
`PROM_URL` / `PROM_USER`	Prometheus remote-write endpoint and user id
`LOKI_URL` / `LOKI_USER`	Loki push endpoint and user id
`GRAFANA_TOKEN`	One Cloud Access Policy token, scopes `metrics:write` + `logs:write` + `fleet-management:read`

Find the values under Grafana Cloud → your stack → Details on each data source, and under Fleet Management. The same token serves remotecfg, Prometheus and Loki basic-auth.

export ALLOY_HOSTNAME=example-host REMOTECFG_ID=example-host ...
docker compose up -d

Run the same file on every host, changing ALLOY_HOSTNAME and REMOTECFG_ID per host. Filter in Grafana with instance=~"...".

Privileges

The upstream Grafana Cloud docker integration runs privileged: true with the raw Docker socket mounted read-write. Nothing in this config needs that, and the combination is host-root-equivalent: privileged grants every capability and unmasks /proc and /sys, and a container that can talk to the Docker socket can start another container that mounts / writable. The socket's :ro flag does not help — it stops the socket file being replaced, not the API being used.

What it runs instead:

Setting	Reason
`cap_drop: [ALL]` + `cap_add: [DAC_OVERRIDE]`	The image's entrypoint runs as uid 0 and reads host files owned by other users — the journal, paths under `/rootfs`, `/var/log`. Dropping every capability leaves it unable to open them, and unable to create its own storage directory. `DAC_OVERRIDE` restores exactly that and nothing else; `SYS_ADMIN`, `NET_ADMIN`, `SYS_PTRACE`, `MKNOD` and the rest stay dropped.
`no-new-privileges:true`	No setuid binary in the image can regain what was dropped.
`mem_limit: 2g`, `pids_limit: 512`	Steady state is around 900 MB; the limit stops a leak taking the host down with it.
`dockerproxy` instead of `/var/run/docker.sock`	See below.

read_only: true is deliberately absent. Compose materialises an inline configs: entry by writing it into the container, and refuses to do that on a read-only service — cannot create config ... : \file` is the sole supported option. Keeping the config inline is worth more than the read-only rootfs here; adding it back means moving the config to a config.alloyfile on disk and switching theconfigs:entry tofile:`.

network_mode: host stays. /proc/net is a symlink to /proc/self/net and resolves against the reading process's network namespace, so bind-mounting the host's /proc to /rootproc is not enough — without host networking the netdev, netstat, sockstat and conntrack families would describe the container's veth pair instead of eth0. That is roughly 45 of the 157 kept metrics.

/:/rootfs:ro also stays, and is the widest remaining exposure: the container can read every file on the host. The filesystem collector needs to statfs() each mount point, and a bind mount cannot grant that without granting reads. Dropping it would cost disk-space monitoring. Treat the container as secret-bearing — it holds GRAFANA_TOKEN regardless.

Docker API access

prometheus.exporter.cadvisor and loki.source.docker both need the Docker API, so it cannot simply be removed. dockerproxy runs tecnativa/docker-socket-proxy with the socket mounted read-only and publishes it on 127.0.0.1:2375, which Alloy reaches over host networking.

POST is revoked by default in that image, which is the point: container create, exec, start and kill are all refused with 403, so a compromise of Alloy can no longer become root on the host. The granted sections are the ones the two components actually call:

Variable	Called by
`CONTAINERS`	`discovery.docker` listing, `loki.source.docker` inspect and log read, cadvisor metadata
`NETWORKS`	`discovery.docker` — Prometheus' Docker SD resolves network names per container, and returns zero targets without it
`IMAGES`, `INFO`, `VERSION`	cadvisor
`EVENTS`	cadvisor container watch (granted by default)

What this does not do: GET /containers/{id}/json still returns every container's environment variables. The proxy closes the escalation path, not the disclosure one.

Mounts

Mount	Why
`/proc:/rootproc:ro`	node-exporter cpu/mem/load, via `procfs_path`
`/sys:/sys:ro`	node-exporter and cadvisor cgroups
`/:/rootfs:ro`	filesystem collector, via `rootfs_path`
`/dev/disk/:/dev/disk:ro`	node-exporter diskstats device labels
`/var/lib/docker:ro`	cadvisor container metadata
`/var/log:/var/log:ro`	`loki.source.journal` and `loki.source.file`
`/etc/machine-id:ro`	Stable host id for the journal reader
`alloy-data`	WAL and remotecfg cache — the only writable path

dockerproxy mounts /var/run/docker.sock:ro and nothing else.

Notes

Upstream sources of truth — what this follows, what is in scope, how to audit dashboard metric needs.
Coolify SSH session noise — only relevant on Coolify-managed hosts.