FEATURE (agent): Setup agent directory, pre-commit and CI\CD workflow

.github/workflows/ci-release.yml

@@ -86,6 +86,39 @@ jobs:
           cd frontend
           npm run build
 
+  lint-agent:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.24.9"
+          cache-dependency-path: agent/go.sum
+
+      - name: Download Go modules
+        run: |
+          cd agent
+          go mod download
+
+      - name: Install golangci-lint
+        run: |
+          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/HEAD/install.sh | sh -s -- -b $(go env GOPATH)/bin v2.7.2
+          echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
+
+      - name: Run golangci-lint
+        run: |
+          cd agent
+          golangci-lint run
+
+      - name: Verify go mod tidy
+        run: |
+          cd agent
+          go mod tidy
+          git diff --exit-code go.mod go.sum || (echo "go mod tidy made changes, please run 'go mod tidy' and commit the changes" && exit 1)
+
   test-frontend:
     runs-on: ubuntu-latest
     needs: [lint-frontend]
@@ -108,6 +141,29 @@ jobs:
           cd frontend
           npm run test
 
+  test-agent:
+    runs-on: ubuntu-latest
+    needs: [lint-agent]
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.24.9"
+          cache-dependency-path: agent/go.sum
+
+      - name: Download Go modules
+        run: |
+          cd agent
+          go mod download
+
+      - name: Run Go tests
+        run: |
+          cd agent
+          go test -count=1 -failfast ./internal/...
+
   test-backend:
     runs-on: self-hosted
     needs: [lint-backend]
@@ -441,7 +497,7 @@ jobs:
     runs-on: self-hosted
     container:
       image: node:20
-    needs: [test-backend, test-frontend]
+    needs: [test-backend, test-frontend, test-agent]
     if: ${{ github.ref == 'refs/heads/main' && !contains(github.event.head_commit.message, '[skip-release]') }}
     outputs:
       should_release: ${{ steps.version_bump.outputs.should_release }}
@@ -534,7 +590,7 @@ jobs:
 
   build-only:
     runs-on: self-hosted
-    needs: [test-backend, test-frontend]
+    needs: [test-backend, test-frontend, test-agent]
     if: ${{ github.ref == 'refs/heads/main' && contains(github.event.head_commit.message, '[skip-release]') }}
     steps:
       - name: Clean workspace

.pre-commit-config.yaml

@@ -41,3 +41,20 @@ repos:
         language: system
         files: ^backend/.*\.go$
         pass_filenames: false
+
+  # Agent checks
+  - repo: local
+    hooks:
+      - id: agent-format-and-lint
+        name: Agent Format & Lint (golangci-lint)
+        entry: bash -c "cd agent && golangci-lint fmt ./internal/... ./cmd/... && golangci-lint run ./internal/... ./cmd/..."
+        language: system
+        files: ^agent/.*\.go$
+        pass_filenames: false
+
+      - id: agent-go-mod-tidy
+        name: Agent Go Mod Tidy
+        entry: bash -c "cd agent && go mod tidy"
+        language: system
+        files: ^agent/.*\.go$
+        pass_filenames: false

Dockerfile

@@ -66,6 +66,43 @@ RUN CGO_ENABLED=0 \
   go build -o /app/main ./cmd/main.go
 
 
+# ========= BUILD AGENT =========
+# Builds the databasus-agent CLI binary for BOTH x86_64 and ARM64.
+# Both architectures are always built because:
+# - Databasus server runs on one arch (e.g. amd64)
+# - The agent runs on remote PostgreSQL servers that may be on a
+#   different arch (e.g. arm64)
+# - The backend serves the correct binary based on the agent's
+#   ?arch= query parameter
+#
+# We cross-compile from the build platform (no QEMU needed) because the
+# agent is pure Go with zero C dependencies.
+# CGO_ENABLED=0 produces fully static binaries — no glibc/musl dependency,
+# so the agent runs on any Linux distro (Alpine, Debian, Ubuntu, RHEL, etc.).
+# APP_VERSION is baked into the binary via -ldflags so the agent can
+# compare its version against the server and auto-update when needed.
+FROM --platform=$BUILDPLATFORM golang:1.24.9 AS agent-build
+
+ARG APP_VERSION=dev
+
+WORKDIR /agent
+
+COPY agent/go.mod ./
+RUN go mod download
+
+COPY agent/ ./
+
+# Build for x86_64 (amd64) — static binary, no glibc dependency
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
+    go build -ldflags "-X main.Version=${APP_VERSION}" \
+    -o /agent-binaries/databasus-agent-linux-amd64 ./cmd/main.go
+
+# Build for ARM64 (arm64) — static binary, no glibc dependency
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=arm64 \
+    go build -ldflags "-X main.Version=${APP_VERSION}" \
+    -o /agent-binaries/databasus-agent-linux-arm64 ./cmd/main.go
+
+
 # ========= RUNTIME =========
 FROM debian:bookworm-slim
 
@@ -220,6 +257,10 @@ COPY backend/migrations ./migrations
 # Copy UI files
 COPY --from=backend-build /app/ui/build ./ui/build
 
+# Copy agent binaries (both architectures) — served by the backend
+# at GET /api/v1/system/agent?arch=amd64|arm64
+COPY --from=agent-build /agent-binaries ./agent-binaries
+
 # Copy .env file (with fallback to .env.production.example)
 COPY backend/.env* /app/
 RUN if [ ! -f /app/.env ]; then \
@@ -397,6 +438,8 @@ fi
 # Create database and set password for postgres user
 echo "Setting up database and user..."
 gosu postgres \$PG_BIN/psql -p 5437 -h localhost -d postgres << 'SQL'
+
+# We use stub password, because internal DB is not exposed outside container
 ALTER USER postgres WITH PASSWORD 'Q1234567';
 SELECT 'CREATE DATABASE databasus OWNER postgres'
 WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'databasus')

agent/.env.example

@@ -0,0 +1 @@
+ENV_MODE=development

agent/.gitignore

@@ -0,0 +1,23 @@
+main
+.env
+docker-compose.yml
+pgdata
+pgdata_test/
+mysqldata/
+mariadbdata/
+main.exe
+swagger/
+swagger/*
+swagger/docs.go
+swagger/swagger.json
+swagger/swagger.yaml
+postgresus-backend.exe
+databasus-backend.exe
+ui/build/*
+pgdata-for-restore/
+temp/
+cmd.exe
+temp/
+valkey-data/
+victoria-logs-data/
+databasus.json

agent/.golangci.yml

@@ -0,0 +1,19 @@
+version: "2"
+
+run:
+  timeout: 5m
+  tests: false
+  concurrency: 4
+
+linters:
+  default: standard
+
+  settings:
+    errcheck:
+      check-type-assertions: true
+
+formatters:
+  enable:
+    - gofmt
+    - golines
+    - goimports

agent/Makefile

@@ -0,0 +1,12 @@
+# Usage: make run ARGS="start --pg-host localhost"
+run:
+	go run cmd/main.go $(ARGS)
+
+build:
+	CGO_ENABLED=0 go build -ldflags "-X main.Version=$(VERSION)" -o databasus-agent ./cmd/main.go
+
+test:
+	go test -count=1 -failfast ./internal/...
+
+lint:
+	golangci-lint fmt ./cmd/... ./internal/... && golangci-lint run ./cmd/... ./internal/...

agent/cmd/main.go

@@ -0,0 +1,173 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"databasus-agent/internal/config"
+	"databasus-agent/internal/features/start"
+	"databasus-agent/internal/features/upgrade"
+	"databasus-agent/internal/logger"
+)
+
+var Version = "dev"
+
+func main() {
+	if len(os.Args) < 2 {
+		printUsage()
+		os.Exit(1)
+	}
+
+	switch os.Args[1] {
+	case "start":
+		runStart(os.Args[2:])
+	case "stop":
+		runStop()
+	case "status":
+		runStatus()
+	case "restore":
+		runRestore(os.Args[2:])
+	case "version":
+		fmt.Println(Version)
+	default:
+		fmt.Fprintf(os.Stderr, "unknown command: %s\n", os.Args[1])
+		printUsage()
+		os.Exit(1)
+	}
+}
+
+func runStart(args []string) {
+	fs := flag.NewFlagSet("start", flag.ExitOnError)
+
+	isDebug := fs.Bool("debug", false, "Enable debug logging")
+	isSkipUpdate := fs.Bool("skip-update", false, "Skip auto-update check")
+
+	cfg := &config.Config{}
+	cfg.LoadFromJSONAndArgs(fs, args)
+
+	if err := cfg.SaveToJSON(); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to save config: %v\n", err)
+	}
+
+	logger.Init(*isDebug)
+	log := logger.GetLogger()
+
+	isDev := checkIsDevelopment()
+	runUpdateCheck(cfg.DatabasusHost, *isSkipUpdate, isDev, log)
+
+	if err := start.Run(cfg, log); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+func runStop() {
+	logger.Init(false)
+	logger.GetLogger().Info("stop: stub — not yet implemented")
+}
+
+func runStatus() {
+	logger.Init(false)
+	logger.GetLogger().Info("status: stub — not yet implemented")
+}
+
+func runRestore(args []string) {
+	fs := flag.NewFlagSet("restore", flag.ExitOnError)
+
+	targetDir := fs.String("target-dir", "", "Target pgdata directory")
+	backupID := fs.String("backup-id", "", "Full backup UUID (optional)")
+	targetTime := fs.String("target-time", "", "PITR target time in RFC3339 (optional)")
+	isYes := fs.Bool("yes", false, "Skip confirmation prompt")
+	isDebug := fs.Bool("debug", false, "Enable debug logging")
+	isSkipUpdate := fs.Bool("skip-update", false, "Skip auto-update check")
+
+	cfg := &config.Config{}
+	cfg.LoadFromJSONAndArgs(fs, args)
+
+	if err := cfg.SaveToJSON(); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to save config: %v\n", err)
+	}
+
+	logger.Init(*isDebug)
+	log := logger.GetLogger()
+
+	isDev := checkIsDevelopment()
+	runUpdateCheck(cfg.DatabasusHost, *isSkipUpdate, isDev, log)
+
+	log.Info("restore: stub — not yet implemented",
+		"targetDir", *targetDir,
+		"backupId", *backupID,
+		"targetTime", *targetTime,
+		"yes", *isYes,
+	)
+}
+
+func printUsage() {
+	fmt.Fprintln(os.Stderr, "Usage: databasus-agent <command> [flags]")
+	fmt.Fprintln(os.Stderr, "")
+	fmt.Fprintln(os.Stderr, "Commands:")
+	fmt.Fprintln(os.Stderr, "  start    Start the agent (WAL archiving + basebackups)")
+	fmt.Fprintln(os.Stderr, "  stop     Stop a running agent")
+	fmt.Fprintln(os.Stderr, "  status   Show agent status")
+	fmt.Fprintln(os.Stderr, "  restore  Restore a database from backup")
+	fmt.Fprintln(os.Stderr, "  version  Print agent version")
+}
+
+func runUpdateCheck(host string, isSkipUpdate bool, isDev bool, log interface {
+	Info(string, ...any)
+	Warn(string, ...any)
+	Error(string, ...any)
+}) {
+	if isSkipUpdate {
+		return
+	}
+
+	if host == "" {
+		return
+	}
+
+	if err := upgrade.CheckAndUpdate(host, Version, isDev, log); err != nil {
+		log.Error("Auto-update failed", "error", err)
+		os.Exit(1)
+	}
+}
+
+func checkIsDevelopment() bool {
+	dir, err := os.Getwd()
+	if err != nil {
+		return false
+	}
+
+	for range 3 {
+		if data, err := os.ReadFile(filepath.Join(dir, ".env")); err == nil {
+			return parseEnvMode(data)
+		}
+
+		if _, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil {
+			return false
+		}
+
+		dir = filepath.Dir(dir)
+	}
+
+	return false
+}
+
+func parseEnvMode(data []byte) bool {
+	for line := range strings.SplitSeq(string(data), "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		parts := strings.SplitN(line, "=", 2)
+		if len(parts) == 2 && strings.TrimSpace(parts[0]) == "ENV_MODE" {
+			return strings.TrimSpace(parts[1]) == "development"
+		}
+	}
+
+	return false
+}

agent/go.mod

@@ -0,0 +1,11 @@
+module databasus-agent
+
+go 1.24.9
+
+require github.com/stretchr/testify v1.11.1
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

agent/go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

agent/internal/config/config.go

@@ -0,0 +1,136 @@
+package config
+
+import (
+	"encoding/json"
+	"flag"
+	"os"
+
+	"databasus-agent/internal/logger"
+)
+
+var log = logger.GetLogger()
+
+const configFileName = "databasus.json"
+
+type Config struct {
+	DatabasusHost string `json:"databasusHost"`
+	DbID          string `json:"dbId"`
+	Token         string `json:"token"`
+
+	flags parsedFlags
+}
+
+// LoadFromJSONAndArgs reads databasus.json into the struct
+// and overrides JSON values with any explicitly provided CLI flags.
+func (c *Config) LoadFromJSONAndArgs(fs *flag.FlagSet, args []string) {
+	c.loadFromJSON()
+	c.initSources()
+
+	c.flags.host = fs.String(
+		"databasus-host",
+		"",
+		"Databasus server URL (e.g. http://your-server:4005)",
+	)
+	c.flags.dbID = fs.String("db-id", "", "Database ID")
+	c.flags.token = fs.String("token", "", "Agent token")
+
+	if err := fs.Parse(args); err != nil {
+		os.Exit(1)
+	}
+
+	c.applyFlags()
+	log.Info("========= Loading config ============")
+	c.logConfigSources()
+	log.Info("========= Config has been loaded ====")
+}
+
+// SaveToJSON writes the current struct to databasus.json.
+func (c *Config) SaveToJSON() error {
+	data, err := json.MarshalIndent(c, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(configFileName, data, 0644)
+}
+
+func (c *Config) loadFromJSON() {
+	data, err := os.ReadFile(configFileName)
+	if err != nil {
+		if os.IsNotExist(err) {
+			log.Info("No databasus.json found, will create on save")
+			return
+		}
+
+		log.Warn("Failed to read databasus.json", "error", err)
+
+		return
+	}
+
+	if err := json.Unmarshal(data, c); err != nil {
+		log.Warn("Failed to parse databasus.json", "error", err)
+
+		return
+	}
+
+	log.Info("Configuration loaded from " + configFileName)
+}
+
+func (c *Config) initSources() {
+	c.flags.sources = map[string]string{
+		"databasus-host": "not configured",
+		"db-id":          "not configured",
+		"token":          "not configured",
+	}
+
+	if c.DatabasusHost != "" {
+		c.flags.sources["databasus-host"] = configFileName
+	}
+
+	if c.DbID != "" {
+		c.flags.sources["db-id"] = configFileName
+	}
+
+	if c.Token != "" {
+		c.flags.sources["token"] = configFileName
+	}
+}
+
+func (c *Config) applyFlags() {
+	if c.flags.host != nil && *c.flags.host != "" {
+		c.DatabasusHost = *c.flags.host
+		c.flags.sources["databasus-host"] = "command line args"
+	}
+
+	if c.flags.dbID != nil && *c.flags.dbID != "" {
+		c.DbID = *c.flags.dbID
+		c.flags.sources["db-id"] = "command line args"
+	}
+
+	if c.flags.token != nil && *c.flags.token != "" {
+		c.Token = *c.flags.token
+		c.flags.sources["token"] = "command line args"
+	}
+}
+
+func (c *Config) logConfigSources() {
+	log.Info(
+		"databasus-host",
+		"value",
+		c.DatabasusHost,
+		"source",
+		c.flags.sources["databasus-host"],
+	)
+	log.Info("db-id", "value", c.DbID, "source", c.flags.sources["db-id"])
+	log.Info("token", "value", maskSensitive(c.Token), "source", c.flags.sources["token"])
+}
+
+func maskSensitive(value string) string {
+	if value == "" {
+		return "(not set)"
+	}
+
+	visibleLen := max(len(value)/4, 1)
+
+	return value[:visibleLen] + "***"
+}

agent/internal/config/config_test.go

@@ -0,0 +1,162 @@
+package config
+
+import (
+	"encoding/json"
+	"flag"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_LoadFromJSONAndArgs_ValuesLoadedFromJSON(t *testing.T) {
+	dir := setupTempDir(t)
+	writeConfigJSON(t, dir, Config{
+		DatabasusHost: "http://json-host:4005",
+		DbID:          "json-db-id",
+		Token:         "json-token",
+	})
+
+	cfg := &Config{}
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	cfg.LoadFromJSONAndArgs(fs, []string{})
+
+	assert.Equal(t, "http://json-host:4005", cfg.DatabasusHost)
+	assert.Equal(t, "json-db-id", cfg.DbID)
+	assert.Equal(t, "json-token", cfg.Token)
+}
+
+func Test_LoadFromJSONAndArgs_ValuesLoadedFromArgs_WhenNoJSON(t *testing.T) {
+	setupTempDir(t)
+
+	cfg := &Config{}
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	cfg.LoadFromJSONAndArgs(fs, []string{
+		"--databasus-host", "http://arg-host:4005",
+		"--db-id", "arg-db-id",
+		"--token", "arg-token",
+	})
+
+	assert.Equal(t, "http://arg-host:4005", cfg.DatabasusHost)
+	assert.Equal(t, "arg-db-id", cfg.DbID)
+	assert.Equal(t, "arg-token", cfg.Token)
+}
+
+func Test_LoadFromJSONAndArgs_ArgsOverrideJSON(t *testing.T) {
+	dir := setupTempDir(t)
+	writeConfigJSON(t, dir, Config{
+		DatabasusHost: "http://json-host:4005",
+		DbID:          "json-db-id",
+		Token:         "json-token",
+	})
+
+	cfg := &Config{}
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	cfg.LoadFromJSONAndArgs(fs, []string{
+		"--databasus-host", "http://arg-host:9999",
+		"--db-id", "arg-db-id-override",
+		"--token", "arg-token-override",
+	})
+
+	assert.Equal(t, "http://arg-host:9999", cfg.DatabasusHost)
+	assert.Equal(t, "arg-db-id-override", cfg.DbID)
+	assert.Equal(t, "arg-token-override", cfg.Token)
+}
+
+func Test_LoadFromJSONAndArgs_PartialArgsOverrideJSON(t *testing.T) {
+	dir := setupTempDir(t)
+	writeConfigJSON(t, dir, Config{
+		DatabasusHost: "http://json-host:4005",
+		DbID:          "json-db-id",
+		Token:         "json-token",
+	})
+
+	cfg := &Config{}
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	cfg.LoadFromJSONAndArgs(fs, []string{
+		"--databasus-host", "http://arg-host-only:4005",
+	})
+
+	assert.Equal(t, "http://arg-host-only:4005", cfg.DatabasusHost)
+	assert.Equal(t, "json-db-id", cfg.DbID)
+	assert.Equal(t, "json-token", cfg.Token)
+}
+
+func Test_SaveToJSON_ConfigSavedCorrectly(t *testing.T) {
+	setupTempDir(t)
+
+	cfg := &Config{
+		DatabasusHost: "http://save-host:4005",
+		DbID:          "save-db-id",
+		Token:         "save-token",
+	}
+
+	err := cfg.SaveToJSON()
+	require.NoError(t, err)
+
+	saved := readConfigJSON(t)
+
+	assert.Equal(t, "http://save-host:4005", saved.DatabasusHost)
+	assert.Equal(t, "save-db-id", saved.DbID)
+	assert.Equal(t, "save-token", saved.Token)
+}
+
+func Test_SaveToJSON_AfterArgsOverrideJSON_SavedFileContainsMergedValues(t *testing.T) {
+	dir := setupTempDir(t)
+	writeConfigJSON(t, dir, Config{
+		DatabasusHost: "http://json-host:4005",
+		DbID:          "json-db-id",
+		Token:         "json-token",
+	})
+
+	cfg := &Config{}
+	fs := flag.NewFlagSet("test", flag.ContinueOnError)
+	cfg.LoadFromJSONAndArgs(fs, []string{
+		"--databasus-host", "http://override-host:9999",
+	})
+
+	err := cfg.SaveToJSON()
+	require.NoError(t, err)
+
+	saved := readConfigJSON(t)
+
+	assert.Equal(t, "http://override-host:9999", saved.DatabasusHost)
+	assert.Equal(t, "json-db-id", saved.DbID)
+	assert.Equal(t, "json-token", saved.Token)
+}
+
+func setupTempDir(t *testing.T) string {
+	t.Helper()
+
+	origDir, err := os.Getwd()
+	require.NoError(t, err)
+
+	dir := t.TempDir()
+	require.NoError(t, os.Chdir(dir))
+
+	t.Cleanup(func() { os.Chdir(origDir) })
+
+	return dir
+}
+
+func writeConfigJSON(t *testing.T, dir string, cfg Config) {
+	t.Helper()
+
+	data, err := json.MarshalIndent(cfg, "", "  ")
+	require.NoError(t, err)
+
+	require.NoError(t, os.WriteFile(dir+"/"+configFileName, data, 0644))
+}
+
+func readConfigJSON(t *testing.T) Config {
+	t.Helper()
+
+	data, err := os.ReadFile(configFileName)
+	require.NoError(t, err)
+
+	var cfg Config
+	require.NoError(t, json.Unmarshal(data, &cfg))
+
+	return cfg
+}

agent/internal/config/dto.go

@@ -0,0 +1,9 @@
+package config
+
+type parsedFlags struct {
+	host  *string
+	dbID  *string
+	token *string
+
+	sources map[string]string
+}

agent/internal/features/start/start.go

@@ -0,0 +1,37 @@
+package start
+
+import (
+	"errors"
+	"log/slog"
+
+	"databasus-agent/internal/config"
+)
+
+func Run(cfg *config.Config, log *slog.Logger) error {
+	if err := validateConfig(cfg); err != nil {
+		return err
+	}
+
+	log.Info("start: stub — not yet implemented",
+		"dbId", cfg.DbID,
+		"hasToken", cfg.Token != "",
+	)
+
+	return nil
+}
+
+func validateConfig(cfg *config.Config) error {
+	if cfg.DatabasusHost == "" {
+		return errors.New("argument databasus-host is required")
+	}
+
+	if cfg.DbID == "" {
+		return errors.New("argument db-id is required")
+	}
+
+	if cfg.Token == "" {
+		return errors.New("argument token is required")
+	}
+
+	return nil
+}

agent/internal/features/upgrade/upgrader.go

@@ -0,0 +1,142 @@
+package upgrade
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+	"syscall"
+	"time"
+)
+
+type Logger interface {
+	Info(msg string, args ...any)
+	Warn(msg string, args ...any)
+	Error(msg string, args ...any)
+}
+
+type versionResponse struct {
+	Version string `json:"version"`
+}
+
+func CheckAndUpdate(databasusHost, currentVersion string, isDev bool, log Logger) error {
+	if isDev {
+		log.Info("Skipping update check (development mode)")
+		return nil
+	}
+
+	serverVersion, err := fetchServerVersion(databasusHost, log)
+	if err != nil {
+		return nil
+	}
+
+	if serverVersion == currentVersion {
+		log.Info("Agent version is up to date", "version", currentVersion)
+		return nil
+	}
+
+	log.Info("Updating agent...", "current", currentVersion, "target", serverVersion)
+
+	selfPath, err := os.Executable()
+	if err != nil {
+		return fmt.Errorf("failed to determine executable path: %w", err)
+	}
+
+	tempPath := selfPath + ".update"
+
+	defer func() {
+		_ = os.Remove(tempPath)
+	}()
+
+	if err := downloadBinary(databasusHost, tempPath); err != nil {
+		return fmt.Errorf("failed to download update: %w", err)
+	}
+
+	if err := os.Chmod(tempPath, 0755); err != nil {
+		return fmt.Errorf("failed to set permissions on update: %w", err)
+	}
+
+	if err := verifyBinary(tempPath, serverVersion); err != nil {
+		return fmt.Errorf("update verification failed: %w", err)
+	}
+
+	if err := os.Rename(tempPath, selfPath); err != nil {
+		return fmt.Errorf("failed to replace binary (try --skip-update if this persists): %w", err)
+	}
+
+	log.Info("Update complete, re-executing...")
+
+	return syscall.Exec(selfPath, os.Args, os.Environ())
+}
+
+func fetchServerVersion(host string, log Logger) (string, error) {
+	client := &http.Client{Timeout: 10 * time.Second}
+
+	resp, err := client.Get(host + "/api/v1/system/version")
+	if err != nil {
+		log.Warn("Could not reach server for update check, continuing", "error", err)
+		return "", err
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		log.Warn(
+			"Server returned non-OK status for version check, continuing",
+			"status",
+			resp.StatusCode,
+		)
+		return "", fmt.Errorf("status %d", resp.StatusCode)
+	}
+
+	var ver versionResponse
+	if err := json.NewDecoder(resp.Body).Decode(&ver); err != nil {
+		log.Warn("Failed to parse server version response, continuing", "error", err)
+		return "", err
+	}
+
+	return ver.Version, nil
+}
+
+func downloadBinary(host, destPath string) error {
+	url := fmt.Sprintf("%s/api/v1/system/agent?arch=%s", host, runtime.GOARCH)
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("server returned %d for agent download", resp.StatusCode)
+	}
+
+	f, err := os.Create(destPath)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+
+	_, err = io.Copy(f, resp.Body)
+
+	return err
+}
+
+func verifyBinary(binaryPath, expectedVersion string) error {
+	cmd := exec.Command(binaryPath, "version")
+
+	output, err := cmd.Output()
+	if err != nil {
+		return fmt.Errorf("binary failed to execute: %w", err)
+	}
+
+	got := strings.TrimSpace(string(output))
+	if got != expectedVersion {
+		return fmt.Errorf("version mismatch: expected %q, got %q", expectedVersion, got)
+	}
+
+	return nil
+}

agent/internal/logger/logger.go

@@ -0,0 +1,47 @@
+package logger
+
+import (
+	"log/slog"
+	"os"
+	"sync"
+	"time"
+)
+
+var (
+	loggerInstance *slog.Logger
+	once           sync.Once
+)
+
+func Init(isDebug bool) {
+	level := slog.LevelInfo
+	if isDebug {
+		level = slog.LevelDebug
+	}
+
+	once.Do(func() {
+		loggerInstance = slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+			Level: level,
+			ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+				if a.Key == slog.TimeKey {
+					a.Value = slog.StringValue(time.Now().Format("2006/01/02 15:04:05"))
+				}
+				if a.Key == slog.LevelKey {
+					return slog.Attr{}
+				}
+
+				return a
+			},
+		}))
+
+		loggerInstance.Info("Text structured logger initialized")
+	})
+}
+
+// GetLogger returns a singleton slog.Logger that logs to the console
+func GetLogger() *slog.Logger {
+	if loggerInstance == nil {
+		Init(false)
+	}
+
+	return loggerInstance
+}

backend/cmd/main.go

@@ -28,6 +28,7 @@ import (
 	"databasus-backend/internal/features/restores"
 	"databasus-backend/internal/features/restores/restoring"
 	"databasus-backend/internal/features/storages"
+	system_agent "databasus-backend/internal/features/system/agent"
 	system_healthcheck "databasus-backend/internal/features/system/healthcheck"
 	system_version "databasus-backend/internal/features/system/version"
 	task_cancellation "databasus-backend/internal/features/tasks/cancellation"
@@ -212,6 +213,7 @@ func setUpRoutes(r *gin.Engine) {
 	userController.RegisterRoutes(v1)
 	system_healthcheck.GetHealthcheckController().RegisterRoutes(v1)
 	system_version.GetVersionController().RegisterRoutes(v1)
+	system_agent.GetAgentController().RegisterRoutes(v1)
 	backups_controllers.GetBackupController().RegisterPublicRoutes(v1)
 	backups_controllers.GetPostgresWalBackupController().RegisterRoutes(v1)
 	databases.GetDatabaseController().RegisterPublicRoutes(v1)

backend/internal/features/system/agent/controller.go

@@ -0,0 +1,48 @@
+package system_agent
+
+import (
+	"net/http"
+	"os"
+	"path/filepath"
+
+	"github.com/gin-gonic/gin"
+)
+
+type AgentController struct{}
+
+func (c *AgentController) RegisterRoutes(router *gin.RouterGroup) {
+	router.GET("/system/agent", c.DownloadAgent)
+}
+
+// DownloadAgent
+// @Summary Download agent binary
+// @Description Download the databasus-agent binary for the specified architecture
+// @Tags system/agent
+// @Produce octet-stream
+// @Param arch query string true "Target architecture" Enums(amd64, arm64)
+// @Success 200 {file} binary
+// @Failure 400 {object} map[string]string
+// @Failure 404 {object} map[string]string
+// @Router /system/agent [get]
+func (c *AgentController) DownloadAgent(ctx *gin.Context) {
+	arch := ctx.Query("arch")
+	if arch != "amd64" && arch != "arm64" {
+		ctx.JSON(http.StatusBadRequest, gin.H{"error": "arch must be amd64 or arm64"})
+		return
+	}
+
+	binaryName := "databasus-agent-linux-" + arch
+	binaryPath := filepath.Join("agent-binaries", binaryName)
+
+	if _, err := os.Stat(binaryPath); os.IsNotExist(err) {
+		ctx.JSON(
+			http.StatusNotFound,
+			gin.H{"error": "agent binary not found for architecture: " + arch},
+		)
+		return
+	}
+
+	ctx.Header("Content-Type", "application/octet-stream")
+	ctx.Header("Content-Disposition", "attachment; filename=databasus-agent")
+	ctx.File(binaryPath)
+}

backend/internal/features/system/agent/di.go

@@ -0,0 +1,7 @@
+package system_agent
+
+var agentController = &AgentController{}
+
+func GetAgentController() *AgentController {
+	return agentController
+}