Merge pull request #17 from profullstack/feat/mailu-stack

Self-host Mailu mail stack at mail.profullstack.com

deploy/mailu/.gitignore

@@ -0,0 +1,3 @@
+mailu.env
+certs/
+data/

deploy/mailu/README.md

@@ -0,0 +1,53 @@
+# deploy/mailu — self-hosted mail for `mail.profullstack.com`
+
+Mailu (Postfix + Dovecot + Roundcube + rspamd) as a Docker Compose stack,
+fronted by the host Caddy. Full setup, DNS, and architecture: [`docs/mail.md`](../../docs/mail.md).
+
+## Files
+
+| File | Purpose |
+|---|---|
+| `docker-compose.yml` | the Mailu services (mail ports on host, HTTP on loopback) |
+| `mailu.env.example` | config template → copy to `mailu.env` and fill secrets |
+| `refresh-certs.sh` | copy Caddy's `mail.$DOMAIN` cert into Mailu, reload (timer) |
+| `provision-mailbox.sh` | create a member mailbox / the gateway master user |
+
+`mailu.env`, `certs/`, and `data/` are gitignored (secrets + state).
+
+## Gateway master user
+
+The agentbbs gateway opens any member's mailbox over IMAP with a single secret,
+using Dovecot's **master user** feature (login `<name>*<master>`). Enable it with
+a Dovecot override so Mailu accepts the `*` separator:
+
+`data/overrides/dovecot/auth-master.conf`:
+
+```
+auth_master_user_separator = *
+passdb {
+  driver = static
+  args = nopassword=y
+  master = yes
+  result_success = continue
+}
+```
+
+Then create the master account and point agentbbs at it:
+
+```bash
+./provision-mailbox.sh --master "$(openssl rand -hex 16)"
+# AGENTBBS_MAIL_MASTER_USER=gateway, AGENTBBS_MAIL_MASTER_PASS=<that secret>
+```
+
+> The exact master-passdb wiring varies by Mailu version; verify against your
+> pinned image before relying on it in production. SMTP submission from the
+> gateway uses the trusted local relay (`127.0.0.1:25`), not the master user.
+
+## Ops
+
+```bash
+docker compose up -d            # start
+docker compose logs -f smtp     # tail Postfix
+docker compose exec admin flask mailu config-export   # DKIM keys, etc.
+docker compose down             # stop
+```

deploy/mailu/docker-compose.yml

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+# Mailu stack for mail.profullstack.com — self-hosted Postfix + Dovecot +
+# Roundcube + rspamd. Coexists with the host Caddy: Mailu owns the mail ports
+# (25/465/587/993/995) and serves HTTP on loopback only; Caddy fronts the
+# webmail at https://mail.profullstack.com and supplies the TLS cert
+# (TLS_FLAVOR=mail, certs copied by refresh-certs.sh).
+#
+# Pinned to a Mailu release; bump deliberately. See docs/mail.md.
+x-environment: &default-environment
+  env_file: mailu.env
+
+services:
+  redis:
+    image: redis:alpine
+    restart: always
+    volumes:
+      - "./data/redis:/data"
+
+  front:
+    image: ghcr.io/mailu/nginx:2024.06
+    restart: always
+    env_file: mailu.env
+    ports:
+      # Mail ports bound on the host; HTTP only on loopback for Caddy.
+      - "25:25"
+      - "465:465"
+      - "587:587"
+      - "993:993"
+      - "995:995"
+      - "127.0.0.1:8080:80"
+    volumes:
+      - "./certs:/certs"
+      - "./data/overrides/nginx:/overrides:ro"
+    depends_on:
+      - redis
+
+  admin:
+    image: ghcr.io/mailu/admin:2024.06
+    restart: always
+    env_file: mailu.env
+    volumes:
+      - "./data/data:/data"
+      - "./data/dkim:/dkim"
+    depends_on:
+      - redis
+
+  imap:
+    image: ghcr.io/mailu/dovecot:2024.06
+    restart: always
+    env_file: mailu.env
+    volumes:
+      - "./data/mail:/mail"
+      - "./data/overrides/dovecot:/overrides:ro"
+    depends_on:
+      - front
+
+  smtp:
+    image: ghcr.io/mailu/postfix:2024.06
+    restart: always
+    env_file: mailu.env
+    volumes:
+      - "./data/mailqueue:/queue"
+      - "./data/overrides/postfix:/overrides:ro"
+    depends_on:
+      - front
+
+  antispam:
+    image: ghcr.io/mailu/rspamd:2024.06
+    restart: always
+    env_file: mailu.env
+    volumes:
+      - "./data/filter:/var/lib/rspamd"
+      - "./data/overrides/rspamd:/overrides:ro"
+    depends_on:
+      - front
+
+  webmail:
+    image: ghcr.io/mailu/roundcube:2024.06
+    restart: always
+    env_file: mailu.env
+    volumes:
+      - "./data/webmail:/data"
+    depends_on:
+      - front

deploy/mailu/mailu.env.example

@@ -0,0 +1,44 @@
+# Mailu configuration for mail.profullstack.com — copy to deploy/mailu/mailu.env
+# and fill the secrets. See docs/mail.md for the full setup (DNS, certs, gateway).
+#
+# Generate secrets with:  openssl rand -hex 16
+
+# --- General -----------------------------------------------------------------
+SECRET_KEY=CHANGEME_16_HEX            # openssl rand -hex 16
+DOMAIN=mail.profullstack.com          # member addresses are <name>@mail.profullstack.com
+HOSTNAMES=mail.profullstack.com,smtp.profullstack.com
+POSTMASTER=postmaster
+# Apex profullstack.com is reserved for corporate mail and is NOT served here.
+
+# TLS_FLAVOR=mail: Mailu does NOT run its own ACME (Caddy owns :80/:443). We feed
+# it certs copied from Caddy's mail.profullstack.com cert (deploy/mailu/refresh-certs.sh).
+TLS_FLAVOR=mail
+
+# --- Features ----------------------------------------------------------------
+ADMIN=true                            # the admin UI (fronted at /admin via Caddy, internal only)
+WEBMAIL=roundcube                     # the only member-facing surface (https://mail.profullstack.com)
+WEBDAV=none
+ANTIVIRUS=none                        # set to clamav on a 4GB+ host
+ANTISPAM=true
+
+# --- Networking --------------------------------------------------------------
+# Mailu's front binds the mail ports on the host and HTTP on loopback only;
+# Caddy reverse-proxies https://mail.profullstack.com to BIND_ADDRESS4:80.
+BIND_ADDRESS4=127.0.0.1
+SUBNET=192.168.203.0/24
+MESSAGE_SIZE_LIMIT=52428800           # 50 MB
+
+# --- Gateway (the BBS reads/sends on behalf of members) ----------------------
+# A Dovecot master user lets the agentbbs gateway open any member's mailbox with
+# one secret (login "<name>*<master>"). Created by deploy/mailu/provision-mailbox.sh.
+# Mirror these into the agentbbs service env:
+#   AGENTBBS_MAIL_DOMAIN=mail.profullstack.com
+#   AGENTBBS_MAIL_IMAP_ADDR=mail.profullstack.com:993
+#   AGENTBBS_MAIL_SMTP_ADDR=127.0.0.1:25
+#   AGENTBBS_MAIL_MASTER_USER=gateway
+#   AGENTBBS_MAIL_MASTER_PASS=<the master password you set>
+
+# --- Admin bootstrap ---------------------------------------------------------
+INITIAL_ADMIN_ACCOUNT=admin
+INITIAL_ADMIN_DOMAIN=mail.profullstack.com
+INITIAL_ADMIN_PW=CHANGEME_admin_password

deploy/mailu/provision-mailbox.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+#
+# provision-mailbox.sh — create or update a member mailbox on the Mailu stack.
+# Run on the mail host. The agentbbs gateway opens any member's mailbox via the
+# Dovecot master user, so members never need an individual IMAP password — but
+# the mailbox must exist, which is what this creates.
+#
+# Usage:
+#   provision-mailbox.sh <name>                 # create <name>@$DOMAIN (random pw)
+#   provision-mailbox.sh --master <pass>        # (re)create the gateway master user
+#
+# Idempotent: re-running for an existing user is a no-op (or a password reset
+# with --password). Wraps Mailu's admin CLI (flask mailu ...).
+set -euo pipefail
+
+MAILU_DIR="${MAILU_DIR:-/opt/agentbbs/deploy/mailu}"
+DOMAIN="${MAIL_DOMAIN:-mail.profullstack.com}"
+MASTER_USER="${AGENTBBS_MAIL_MASTER_USER:-gateway}"
+QUOTA_BYTES="${MAIL_QUOTA_BYTES:-1000000000}" # 1 GB
+
+cli() { ( cd "$MAILU_DIR" && docker compose exec -T admin flask mailu "$@" ); }
+
+if [ "${1:-}" = "--master" ]; then
+  pass="${2:?usage: provision-mailbox.sh --master <password>}"
+  # A Dovecot master user can authenticate as any mailbox: login "<name>*gateway".
+  # Implemented in Mailu as a normal user flagged for master access via an
+  # override (see docs/mail.md); here we ensure the account + password exist.
+  cli user "$MASTER_USER" "$DOMAIN" "$pass" 2>/dev/null \
+    || cli password "$MASTER_USER" "$DOMAIN" "$pass"
+  echo "gateway master user ${MASTER_USER}@${DOMAIN} set"
+  exit 0
+fi
+
+name="${1:?usage: provision-mailbox.sh <name>}"
+pass="${2:-$(openssl rand -hex 16)}"
+
+if cli user-import "$name" "$DOMAIN" "$(openssl passwd -6 "$pass")" 2>/dev/null; then
+  :
+else
+  # already exists or older CLI: fall back to `user` (no-op if present)
+  cli user "$name" "$DOMAIN" "$pass" 2>/dev/null || true
+fi
+# Enforce a per-mailbox quota.
+cli config-update <<EOF 2>/dev/null || true
+users:
+  - email: ${name}@${DOMAIN}
+    quota_bytes: ${QUOTA_BYTES}
+EOF
+
+echo "mailbox ${name}@${DOMAIN} provisioned"

deploy/mailu/refresh-certs.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+#
+# refresh-certs.sh — copy Caddy's Let's Encrypt cert for mail.$DOMAIN into the
+# Mailu certs dir (TLS_FLAVOR=mail), so Postfix/Dovecot TLS on 465/587/993 track
+# Caddy's auto-renewals. Mirrors deploy/news-refresh-certs.sh: Caddy is the only
+# ACME client on the box (it serves the mail.$DOMAIN site block), and we reuse
+# that cert rather than running a second ACME client inside Mailu.
+#
+# Install to /usr/local/bin/agentbbs-mailu-certs and run from a timer. Reloads
+# the Mailu front/smtp/imap so the new cert is picked up. Exits non-zero
+# (touching nothing) until Caddy has issued the cert.
+set -euo pipefail
+
+DOMAIN="${DOMAIN:?set DOMAIN}"
+MAIL_HOST="${MAIL_HOST:-mail.${DOMAIN}}"
+MAILU_DIR="${MAILU_DIR:-/opt/agentbbs/deploy/mailu}"
+CERT_DIR="${CERT_DIR:-$MAILU_DIR/certs}"
+CADDY_DATA="${CADDY_DATA:-/var/lib/caddy/.local/share/caddy}"
+
+# Caddy stores certs under certificates/<acme-dir>/<host>/<host>.{crt,key};
+# the ACME directory segment varies (prod vs staging), so glob for it.
+crt="$(ls "$CADDY_DATA"/certificates/*/"$MAIL_HOST"/"$MAIL_HOST".crt 2>/dev/null | head -1 || true)"
+key="$(ls "$CADDY_DATA"/certificates/*/"$MAIL_HOST"/"$MAIL_HOST".key 2>/dev/null | head -1 || true)"
+if [ -z "$crt" ] || [ -z "$key" ]; then
+  echo "no Caddy cert for $MAIL_HOST yet (looked under $CADDY_DATA/certificates)"
+  exit 1
+fi
+
+install -d -m 0750 "$CERT_DIR"
+
+changed=0
+# Mailu (TLS_FLAVOR=mail) reads cert.pem / key.pem from its /certs mount.
+if ! cmp -s "$crt" "$CERT_DIR/cert.pem"; then install -m 0644 "$crt" "$CERT_DIR/cert.pem"; changed=1; fi
+if ! cmp -s "$key" "$CERT_DIR/key.pem"; then install -m 0640 "$key" "$CERT_DIR/key.pem"; changed=1; fi
+
+if [ "$changed" = 1 ]; then
+  echo "updated Mailu TLS cert for $MAIL_HOST; reloading Mailu"
+  ( cd "$MAILU_DIR" && docker compose restart front smtp imap >/dev/null 2>&1 || true )
+else
+  echo "Mailu TLS cert for $MAIL_HOST already current"
+fi

docs/mail.md

@@ -0,0 +1,118 @@
+# Mail — self-hosted Mailu at `mail.profullstack.com`
+
+AgentBBS gives **Founding Lifetime (paid) members** a real mailbox at
+`<name>@mail.profullstack.com`, reached two ways:
+
+- **Webmail** — `https://mail.profullstack.com` (Roundcube), the only
+  member-facing mail surface.
+- **AgentMail** — the in-BBS client (`internal/mailbox`): the `Mail` hub entry
+  or `ssh mail@bbs.profullstack.com` (a TUI for humans, a JSON bot mode for
+  agents). It connects to this stack.
+
+The apex `profullstack.com` is **reserved for corporate mail** and is not served
+here — member mail lives only on the `mail.` subdomain.
+
+## Architecture
+
+The host already runs **Caddy** (owns `:80`/`:443`) and the **agentbbs** process.
+Mailu (Postfix + Dovecot + Roundcube + rspamd) runs as a Docker Compose stack:
+
+- Mailu owns the **mail ports** on the host: `25, 465, 587, 993, 995`.
+- Mailu's HTTP front is bound to **loopback** (`127.0.0.1:8080`); **Caddy**
+  reverse-proxies `https://mail.profullstack.com` to it (webmail + admin).
+- **TLS:** `TLS_FLAVOR=mail` — Mailu does *not* run its own ACME (Caddy is the
+  only ACME client). Caddy obtains the `mail.profullstack.com` cert from its site
+  block; [`deploy/mailu/refresh-certs.sh`](../deploy/mailu/refresh-certs.sh)
+  copies it into Mailu and reloads it on renewal — the same pattern as the
+  Ergo/IRC and NNTP cert refreshers.
+- The **agentbbs gateway** reads/sends on behalf of members: IMAP via a Dovecot
+  **master user** (one secret opens any mailbox), SMTP via the co-located relay
+  on `127.0.0.1:25`. Members therefore never manage an IMAP/SMTP password.
+
+```
+            ┌─────────── Caddy (:443) ───────────┐
+ webmail →  │ mail.profullstack.com → 127.0.0.1:8080 (Mailu front, HTTP)
+            └───────────────┬─────────────────────┘
+                            │ copies LE cert (refresh-certs.sh)
+ clients →  Mailu front (:25 :465 :587 :993 :995)  ──→ Postfix / Dovecot / rspamd
+                            ▲
+ agentbbs ──IMAP 993 (master user)──┘   ──SMTP 127.0.0.1:25 (local relay)──▶
+```
+
+## DNS
+
+`mail.profullstack.com` and `smtp.profullstack.com` A records are added. Also set:
+
+| Type | Host | Value |
+|---|---|---|
+| A | `mail.profullstack.com` | host IP |
+| A | `smtp.profullstack.com` | host IP |
+| MX | `mail.profullstack.com` | `10 mail.profullstack.com.` |
+| TXT (SPF) | `mail.profullstack.com` | `v=spf1 mx -all` |
+| TXT (DMARC) | `_dmarc.mail.profullstack.com` | `v=DMARC1; p=quarantine; rua=mailto:postmaster@mail.profullstack.com` |
+| TXT (DKIM) | `dkim._domainkey.mail.profullstack.com` | from `flask mailu config-export` after first boot |
+| PTR | host IP | `mail.profullstack.com` (set at your VPS provider) |
+
+> **Port 25 / deliverability:** many cloud providers block outbound `:25` by
+> default — request an unblock, set the PTR/rDNS, and warm the IP, or relay
+> outbound through a smarthost. Inbound MX and the gateway's local submission
+> work regardless.
+
+## Install
+
+```bash
+cd /opt/agentbbs/deploy/mailu
+cp mailu.env.example mailu.env      # fill SECRET_KEY, INITIAL_ADMIN_PW, etc.
+docker compose up -d
+# seed the gateway master user + (optionally) backfill member mailboxes:
+AGENTBBS_MAIL_MASTER_USER=gateway ./provision-mailbox.sh --master "$(openssl rand -hex 16)"
+```
+
+Add the Caddy site (setup.sh writes this when `MAIL=1`):
+
+```
+mail.profullstack.com {
+    encode zstd gzip
+    reverse_proxy 127.0.0.1:8080
+}
+```
+
+Then install the cert refresher on a timer (setup.sh does this too):
+
+```bash
+install -m 0755 deploy/mailu/refresh-certs.sh /usr/local/bin/agentbbs-mailu-certs
+# systemd timer runs it every ~12h; first run swaps in the real cert once Caddy issues it.
+```
+
+## agentbbs gateway env
+
+Set these on the agentbbs service so the `Mail` hub entry / `ssh mail@` work:
+
+| Var | Value |
+|---|---|
+| `AGENTBBS_MAIL_DOMAIN` | `mail.profullstack.com` |
+| `AGENTBBS_MAIL_IMAP_ADDR` | `mail.profullstack.com:993` |
+| `AGENTBBS_MAIL_SMTP_ADDR` | `127.0.0.1:25` |
+| `AGENTBBS_MAIL_MASTER_USER` | `gateway` |
+| `AGENTBBS_MAIL_MASTER_PASS` | the master password set above |
+
+## Provisioning member mailboxes
+
+A mailbox must exist before the gateway can open it. Provision when a member
+becomes paid (or backfill):
+
+```bash
+deploy/mailu/provision-mailbox.sh alice      # creates alice@mail.profullstack.com
+```
+
+The Dovecot **master user** (`gateway`) then authenticates as any member with
+the login form `alice*gateway` + the master password — which is exactly what
+`internal/mailbox`'s IMAP adapter sends. See
+[`deploy/mailu/README.md`](../deploy/mailu/README.md) for the master-user
+override and operational details.
+
+## Webmail only for members
+
+Members are pointed at `https://mail.profullstack.com` (Roundcube) and the BBS
+`Mail` client — they are not given the Mailu admin UI or alias management. Admin
+is operator-only.

setup.sh

@@ -47,6 +47,8 @@ ERGO_DATA="${ERGO_DATA:-/var/lib/ergo}"  # Ergo state dir (ircd.db, tls/)
 FORGEJO="${FORGEJO:-1}"                  # set 0 to skip the AgentGit Forgejo backend (git.${DOMAIN#*.})
 GIT_DOMAIN="${GIT_DOMAIN:-git.${DOMAIN#*.}}"  # AgentGit host (default: git.<root-of-DOMAIN>, e.g. git.profullstack.com)
 FORGEJO_VERSION="${FORGEJO_VERSION:-11.0.1}"  # Forgejo release to install
+MAIL="${MAIL:-1}"                   # set 0 to skip the co-located Mailu mail stack (mail.${DOMAIN#*.})
+MAIL_DOMAIN="${MAIL_DOMAIN:-mail.${DOMAIN#*.}}"  # mail host (default: mail.<root-of-DOMAIN>, e.g. mail.profullstack.com)
 FORGEJO_HTTP_ADDR="${FORGEJO_HTTP_ADDR:-127.0.0.1:3000}"  # Forgejo loopback HTTP (Caddy fronts it)
 FORGEJO_DATA="${FORGEJO_DATA:-/var/lib/forgejo}"  # Forgejo state dir (repos, db)
 FORGEJO_ADMIN_USER="${FORGEJO_ADMIN_USER:-agentgit-admin}"  # Forgejo admin used to provision members
@@ -502,6 +504,20 @@ ${IRC_DOMAIN} {
 "
 fi
 
+# Mail site (${MAIL_DOMAIN}): Caddy serving this host obtains the LE cert that
+# Mailu reuses for SMTP/IMAP TLS (deploy/mailu/refresh-certs.sh copies it). It
+# also fronts the loopback Roundcube webmail. Needs A record ${MAIL_DOMAIN} ->
+# this host. Webmail is the only member-facing mail surface. Omitted when MAIL=0.
+MAIL_SITE=""
+if [ "$MAIL" = "1" ]; then
+  MAIL_SITE="
+${MAIL_DOMAIN} {
+	encode zstd gzip
+	reverse_proxy 127.0.0.1:8080
+}
+"
+fi
+
 cat > /etc/caddy/Caddyfile <<CADDY
 {
 	email ${ACME_EMAIL}
@@ -545,7 +561,7 @@ ${DOMAIN} {
 		file_server
 	}
 }
-${GIT_SITE}${NEWS_SITE}${IRC_SITE}
+${GIT_SITE}${NEWS_SITE}${IRC_SITE}${MAIL_SITE}
 # Free per-user homepages at <name>.${DOMAIN} (needs wildcard DNS
 # *.${DOMAIN} -> this host). On-demand TLS mints a cert only when agentbbs's
 # ask endpoint confirms <name> is a registered member, so random subdomains
@@ -923,6 +939,61 @@ else
   systemctl disable --now forgejo >/dev/null 2>&1 || true
 fi
 
+# ---- 9e. Mailu mail stack (co-located mail.${DOMAIN#*.}) --------------------
+# Self-hosted Postfix+Dovecot+Roundcube+rspamd via Docker Compose. Mailu owns
+# the mail ports; Caddy fronts the loopback webmail and supplies the TLS cert
+# (TLS_FLAVOR=mail). agentbbs reads/sends on behalf of paid members. Full setup,
+# DNS, and the gateway master user: docs/mail.md. Disable with MAIL=0.
+MAILU_DIR="${SRC_DIR}/deploy/mailu"
+if [ "$MAIL" = "1" ]; then
+  log "configuring Mailu mail stack (${MAIL_DOMAIN})"
+  # Tell agentbbs how to reach the mailbox backend (master user/pass are secrets
+  # the operator sets; see docs/mail.md).
+  upsert_env AGENTBBS_MAIL_DOMAIN "${MAIL_DOMAIN}"
+  upsert_env AGENTBBS_MAIL_IMAP_ADDR "${MAIL_DOMAIN}:993"
+  upsert_env AGENTBBS_MAIL_SMTP_ADDR "127.0.0.1:25"
+
+  # Cert refresher: copy Caddy's mail cert into Mailu on renewal (like news/IRC).
+  install -m 0755 "${MAILU_DIR}/refresh-certs.sh" /usr/local/bin/agentbbs-mailu-certs
+  cat > /etc/systemd/system/agentbbs-mailu-certs.service <<UNIT
+[Unit]
+Description=Refresh Mailu TLS cert from Caddy for ${MAIL_DOMAIN}
+
+[Service]
+Type=oneshot
+Environment=DOMAIN=${DOMAIN#*.}
+Environment=MAIL_HOST=${MAIL_DOMAIN}
+Environment=MAILU_DIR=${MAILU_DIR}
+ExecStart=/usr/local/bin/agentbbs-mailu-certs
+UNIT
+  cat > /etc/systemd/system/agentbbs-mailu-certs.timer <<UNIT
+[Unit]
+Description=Periodic Mailu TLS cert refresh from Caddy
+
+[Timer]
+OnBootSec=5min
+OnUnitActiveSec=12h
+Persistent=true
+
+[Install]
+WantedBy=timers.target
+UNIT
+  systemctl daemon-reload
+  systemctl enable --now agentbbs-mailu-certs.timer >/dev/null 2>&1 || true
+
+  # Open the mail ports; bring Mailu up only once the operator has created
+  # mailu.env (it carries SECRET_KEY + admin password — never auto-generated).
+  for p in 25 465 587 993 995; do ufw allow "${p}/tcp" >/dev/null; done
+  if command -v docker >/dev/null && [ -f "${MAILU_DIR}/mailu.env" ]; then
+    ( cd "$MAILU_DIR" && docker compose up -d ) || warn "mailu: docker compose up failed — check ${MAILU_DIR}"
+  else
+    warn "Mailu not started yet: create ${MAILU_DIR}/mailu.env (cp mailu.env.example) and run 'docker compose up -d' — see docs/mail.md"
+  fi
+else
+  upsert_env AGENTBBS_MAIL_DOMAIN ""
+  systemctl disable --now agentbbs-mailu-certs.timer >/dev/null 2>&1 || true
+fi
+
 # ---- 10. firewall + start agentbbs on :22 ----------------------------------
 log "configuring firewall + starting agentbbs"
 ufw allow 22/tcp >/dev/null