fix: remove linux-patch-api user from dpkg scripts, change ownership to root

- Remove user/group creation from preinst (service runs as root)
- Change directory ownership to root:root in preinst and postinst
- Remove user/group deletion from postrm
- Service runs as root, no dedicated user needed

debian/postinst

@@ -13,14 +13,14 @@ if [ "$1" = "configure" ]; then
         echo "Creating default config.yaml..."
         cp /etc/linux_patch_api/config.yaml.example /etc/linux_patch_api/config.yaml
         chmod 640 /etc/linux_patch_api/config.yaml
-        chown linux-patch-api:linux-patch-api /etc/linux_patch_api/config.yaml
+        chown root:root /etc/linux_patch_api/config.yaml
     fi
     
     if [ ! -f "/etc/linux_patch_api/whitelist.yaml" ]; then
         echo "Creating default whitelist.yaml..."
         cp /etc/linux_patch_api/whitelist.yaml.example /etc/linux_patch_api/whitelist.yaml
         chmod 640 /etc/linux_patch_api/whitelist.yaml
-        chown linux-patch-api:linux-patch-api /etc/linux_patch_api/whitelist.yaml
+        chown root:root /etc/linux_patch_api/whitelist.yaml
     fi
     
     # Reload systemd daemon to pick up new service file

debian/postrm

@@ -39,18 +39,6 @@ if [ "$1" = "purge" ]; then
         rm -rf /var/log/linux_patch_api
     fi
     
-    # Remove system user
-    if getent passwd linux-patch-api > /dev/null 2>&1; then
-        echo "Removing user linux-patch-api..."
-        userdel linux-patch-api 2>/dev/null || true
-    fi
-    
-    # Remove system group
-    if getent group linux-patch-api > /dev/null 2>&1; then
-        echo "Removing group linux-patch-api..."
-        groupdel linux-patch-api 2>/dev/null || true
-    fi
-    
     echo "linux-patch-api purged successfully"
 fi
 

debian/preinst

@@ -9,31 +9,14 @@ if [ -d "/etc/linux_patch_api" ]; then
     echo "Detected existing installation - performing upgrade"
 fi
 
-# Create system user if it doesn't exist
-if ! getent group linux-patch-api > /dev/null 2>&1; then
-    echo "Creating group linux-patch-api..."
-    groupadd --system linux-patch-api
-fi
-
-if ! getent passwd linux-patch-api > /dev/null 2>&1; then
-    echo "Creating user linux-patch-api..."
-    useradd --system \
-        --gid linux-patch-api \
-        --home-dir /var/lib/linux_patch_api \
-        --no-create-home \
-        --shell /usr/sbin/nologin \
-        --comment "Linux Patch API Service" \
-        linux-patch-api
-fi
-
 # Create required directories
 mkdir -p /etc/linux_patch_api/certs
 mkdir -p /var/lib/linux_patch_api
 mkdir -p /var/log/linux_patch_api
 
-# Set proper ownership
-chown -R linux-patch-api:linux-patch-api /var/lib/linux_patch_api
-chown -R linux-patch-api:linux-patch-api /var/log/linux_patch_api
+# Set proper ownership (service runs as root)
+chown -R root:root /var/lib/linux_patch_api
+chown -R root:root /var/log/linux_patch_api
 
 # Set secure permissions
 chmod 750 /etc/linux_patch_api

tasks/lessons.md

@@ -47,3 +47,27 @@
 **Correction:** Add `sudo apt-get -f install -y` before `sudo apt-get install` in CI workflow to fix broken deps automatically.
 **Rule:** Always add `apt-get -f install -y` before `apt-get install` in CI workflows. Runners may have broken apt state from partial upgrades.
 **Status:** Active
+
+## 2026-05-03 - NoNewPrivileges=true blocks sudo in systemd services
+**Mistake:** Service used NoNewPrivileges=true which prevented sudo from working (PERM_SUDOERS: setresuid Operation not permitted).
+**Correction:** Removed NoNewPrivileges=true from systemd service. The service runs as root and uses sudo for apt commands, which requires privilege escalation capabilities.
+**Rule:** For package management services that use sudo, do not use NoNewPrivileges=true. mTLS + IP whitelist provides network security.
+**Status:** Active
+
+## 2026-05-03 - RestrictSUIDSGID=true blocks sudo in systemd services
+**Mistake:** Service used RestrictSUIDSGID=true which prevented sudo from using setuid/setgid operations.
+**Correction:** Removed RestrictSUIDSGID=true from systemd service. Package management requires setuid/setgid for apt/dpkg.
+**Rule:** For package management services, do not use RestrictSUIDSGID=true. It blocks sudo and apt from working.
+**Status:** Active
+
+## 2026-05-03 - dpkg preinst creates linux-patch-api user causing permission issues
+**Mistake:** dpkg preinst script creates a linux-patch-api system user and changes directory ownership, causing the service to crash with 'Permission denied' on log file creation.
+**Correction:** Fix dpkg preinst to not create the linux-patch-api user or change directory ownership. Service runs as root and directories should be owned by root.
+**Rule:** For services that run as root, do not create a dedicated system user in the dpkg preinst script. Keep all directory ownership as root:root.
+**Status:** Active
+
+## 2026-05-03 - Service runs as root, no sudo needed for apt commands
+**Mistake:** Service used sudo to run apt commands even though it runs as root. This caused failures when systemd security restrictions blocked sudo.
+**Correction:** Removed sudo from apt command execution in the source code. Service runs as root and can execute apt directly.
+**Rule:** If a service runs as root, it does not need sudo to execute commands. Remove sudo from command execution.
+**Status:** Active