Multiple improvements

Re-organize the repository. Improve permission model (use internal mail user to send mails).
Add more instructions about how to set-up.

README.md

@@ -20,9 +20,9 @@ This repository contains a systemd service file & a simple bash script to refres
 
 - Linux OS
 
-    - systemd - service file
+    - systemd
 
-    - [SSMTP](https://wiki.archlinux.org/index.php/SSMTP) - (SMTP) email client (package: `ssmtp` (Arch Linux), `ssmtp` (Ubuntu))
+    - [sSMTP](https://wiki.archlinux.org/index.php/SSMTP) - (SMTP) email client (package: `ssmtp` (Arch Linux), `ssmtp` (Ubuntu))
 
     - dig (package: `bind-tools` (Arch Linux), `dnsutils` (Ubuntu))
 
@@ -32,44 +32,42 @@ This repository contains a systemd service file & a simple bash script to refres
 
 ## Contents
 
-- systemd **system** service file: `wanchecker@.service`
+- systemd **system** service file: [wanchecker.service](wanchecker.service)
 
-- systemd **system** timer file: `wanchecker@.timer`
+- systemd **system** timer file: [wanchecker.timer](wanchecker.timer)
 
-- bash script: `wanchecker.sh`
+- [sSMTP sample configuration files](ssmtp_conf-sample)
 
-## Installation
+    - [ssmtp.conf](ssmtp_conf-sample/ssmtp.conf)
+    
+    - [revaliases](ssmtp_conf-sample/revaliases)
+    
+    - [wanchecker.sh](ssmtp_conf-sample/wanchecker.sh)
 
-Configuration can be splitted into two parts as follows.
+## Installation & configuration
 
-### ssmtp
+**1)** Install `ssmtp` package
 
-To-be-added
+**2)** Configure files `/etc/ssmtp/revaliases` ([sample](ssmtp_conf-sample/revaliases)) and `/etc/ssmtp/ssmtp.conf` ([sample](ssmtp_conf-sample/ssmtp.conf)). More information about these files on [sSMTP Arch Wiki site](https://wiki.archlinux.org/index.php/SSMTP).
 
-### wanip-checker
+**3)** Insert [wanchecker.sh](ssmtp_conf-sample/wanchecker.sh) into `/etc/ssmtp/` folder.
 
-**1)** Insert `wanchecker@.service` and `wanchecker@.timer` into `/usr/lib/systemd/system/` folder
+**4)** Configure sSMTP as described in [sSMTP Readme file](ssmtp_conf-sample/README.md).
 
-- WAN IP check interval is customizable in systemd timer file. Default value is `20min`
-
-**2)** Insert `wanchecker.sh` into your `/home/myuser/` folder (where `myuser` is your real username on your Linux system)
-
-**3)** Configure your email address and message form in `wanchecker.sh` file. Configure WAN IPv4 log file location (default is `$HOME`)
+**5)** Insert `wanchecker.service` and `wanchecker.timer` into `/usr/lib/systemd/system/` folder
 
-- log file is updated only when WAN IPv4 changes have been detected
+- WAN IP check interval is customizable in systemd timer file. Default value is `20min`
 
-**3)** Install `ssmtp`, and configure files `/etc/ssmtp/revaliases` and `/etc/ssmtp/ssmtp.conf` as described on [SSMTP Arch Wiki site](https://wiki.archlinux.org/index.php/SSMTP).
+- This log file is updated only when WAN IPv4 changes have been detected
 
-**4)** Run (as root or with `sudo)
+**6)** Run (as root or with `sudo`)
 
 ```
-systemctl enable wanchecker@my_system_username.timer && \
-systemctl start wanchecker@my_system_username.timer
+systemctl enable wanchecker.timer && \
+systemctl start wanchecker.timer
 
 ```
 
-where `my_system_username` refers to your true username on your Linux system.
-
 ## Images
 
 When server computer discovers a change in its WAN IPv4, it automatically sends an email notification to system administrator(s):
@@ -84,9 +82,9 @@ Additionally, server computer keeps a log file which include WAN IPv4 changes an
 
 - `systemctl --all list-timers` = list all system timers on Linux system, including `wanchecker`
 
-- `systemctl is-active wanchecker@my_system_username.timer` = tells whether wanchecker is running or not
+- `systemctl is-active wanchecker.timer` = tells whether `wanchecker` is running or not
 
-- `systemctl status wanchecker@my_system_username.timer` = more compherensive output about the status of `wanchecker`
+- `systemctl status wanchecker.timer` = more compherensive output about the status of `wanchecker`
 
 ## License
 

ssmtp_conf-sample/README.md

@@ -1,26 +1,28 @@
 ## sSMTP system pre-configuration
 
-Once you have installed sSMTP on your Linux system, make sure the following applies. Run the configuration commands as root or with `sudo` prefix.
+Once you have installed sSMTP on your Linux system, make sure the following applies. Run these configuration commands as root or with `sudo`.
 
 ----------
 
-Symbolic link from `/usr/bin/ssmtp` to `/usr/bin/sendmail`:
+**1)** Create symbolic link from `/usr/bin/ssmtp` to `/usr/bin/sendmail` exists:
 
 ```
 ln -s /usr/bin/ssmtp /usr/bin/sendmail
 ```
 
-```
 Test:
 
-    > stat -c "%A %a %U:%G %N" /usr/bin/sendmail
+```
+> stat -c "%A %a %U:%G %N" /usr/bin/sendmail
 
-        lrwxrwxrwx 777 root:root /usr/bin/sendmail -> ssmtp
+    lrwxrwxrwx 777 root:root /usr/bin/sendmail -> ssmtp
 ```
 
 ----------
 
-User & group mail exists, directory /`var/spool/mail` exists:
+**NOTE:** User & group `mail` are defined on Arch Linux by default, preinstalled with `filesystem` package. If they do not exist, then do the following.
+
+**2)** Make sure user & group `mail` exists, and directory /`var/spool/mail` exists with proper permissions:
 
 ```
 mkdir -p /var/spool/mail
@@ -30,36 +32,66 @@ groupadd -g 12 mail
 useradd -r -d /var/spool/mail -s /sbin/nologin -u 12 -g 12 mail
 ```
 
-```
 Test:
 
+```
+
 -----
-    > sudo stat -c "%A %a %U:%G %n" /var/spool/mail
+> sudo stat -c "%A %a %U:%G %n" /var/spool/mail
 
-        drwxrwxrwt 1777 root:root /var/spool/mail
+    drwxrwxrwt 1777 root:root /var/spool/mail
 
 -----
-    > grep mail /etc/passwd
+> grep mail /etc/passwd
 
-        mail:x:12:12::/var/spool/mail:/sbin/nologin
+    mail:x:12:12::/var/spool/mail:/sbin/nologin
 
 -----
-    > grep mail /etc/group
+> grep mail /etc/group
 
-        mail:x:12:
+    mail:x:12:
 ```
 
 ## sSMTP configuration files
 
-Once you have sSMTP installed on your Linux system, insert [ssmtp.conf](ssmtp.conf), [revaliases](revaliases) and [wanchecker.sh](wanchecker.sh) into `/etc/ssmtp/` folder. These files should have following permissions:
+Once you have sSMTP installed on your Linux system, configure [ssmtp.conf](ssmtp.conf) and [revaliases](revaliases) in `/etc/ssmtp/` folder.
+
+## Mail message formatting & email address
+
+Configure your message defined in [wanchecker.sh](wanchecker.sh) file.
+
+`wanchecker.sh` variables:
+
+|     Variable     |                                    Value                                    |    Type    |
+|------------------|-----------------------------------------------------------------------------|------------|
+| EMAIL_SENDER     | Sender's address                                                            | String     |
+| EMAIL_RECIPIENTS | Email recipients. Multiple allowed                                          | Bash array |
+| SUBJECT_EMAIL    | Email title                                                                 | String     |
+| MESSAGE_EMAIL    | Email message contents                                                      | String     |
+| MESSAGE_STDOUT   | Internal Linux system message about sent email message                      | String     |
+| WANIP_DIR        | Log file directory path. User `mail` must have write access to this folder. | String     |
+| WANIP_LOG        | Log file name                                                               | String     |
+
+**NOTE:** At minimum, you should configure proper email addresses in variables `EMAIL_SENDER` and `EMAIL_RECIPIENTS`. `EMAIL_SENDER` takes same value as defined in `/etc/ssmtp/ssmtp.conf` ([sample](ssmtp.conf)) and `/etc/ssmtp/revaliases` ([sample](revaliases)) files.
+
+## Folder & file permissions
+
+Permissions for `/etc/ssmtp` folder should be:
 
 ```
-> stat -c "%A %a %U:%G %n" /etc/ssmtp/*
+> stat -c "%A %a %U:%G %n" /etc/ssmtp
 
--rw-r----- 640 root:mail /etc/ssmtp/revaliases
--rw-r----- 640 root:mail /etc/ssmtp/ssmtp.conf
--rwxr-x--- 750 root:mail /etc/ssmtp/wanchecker.sh
+    drwxr-x--- 750 root:mail /etc/ssmtp
+```
+
+Contents of `/etc/ssmtp/` folder should contain the following files & permissions:
+
+```
+> stat -c "%A %a %U:%G %n" /etc/ssmtp/*
 
+    -rw-r----- 640 root:mail /etc/ssmtp/revaliases
+    -rw-r----- 640 root:mail /etc/ssmtp/ssmtp.conf
+    -rwxr-x--- 750 root:mail /etc/ssmtp/wanchecker.sh
 ```
 
-where group `mail` refers to Arch Linux mail group, preinstalled with `filesystem` package.
+**NOTE:** As `/etc/ssmtp/ssmtp.conf` contains a _clear-text email password_, the file must be protected from any eavesdropping with correct permission policy! The file must not be readable to any other than `mail` user, and `mail` user must not be available for normal usage. Still, any `sudo` group member can access the file, so make sure `sudo` group does not contain hostile or unwanted members, and configure your `/etc/sudoers` file properly.

ssmtp_conf-sample/revaliases

@@ -5,4 +5,4 @@
 # Example: root:your_login@your.domain:mailhub.your.domain[:port]
 # where [:port] is an optional port number that defaults to 25.
 
-my_system_username:mailsender@foo.com:smtp.live.com:587
+mail:mailsender@foo.com:smtp.live.com:587

wanchecker.sh → ssmtp_conf-sample/wanchecker.sh

@@ -27,7 +27,7 @@
 
 # Script requirements
 #
-# SSMTP
+# sSMTP
 
 # https://wiki.archlinux.org/index.php/SSMTP
 # Relevant conf files
@@ -81,10 +81,10 @@ function checkWANIP {
 ############################
 
     # Cache/Log directory of the script
-    local WANIP_DIR="$HOME"
+    local WANIP_DIR="/var/spool/mail"
 
     # Log file for checked/resolved IPv4 WAN addresses
-    local WANIP_LOG="$WANIP_DIR/.ip_wan.log"
+    local WANIP_LOG="$WANIP_DIR/ip_wan.log"
 
     if [[ ! -d "${WANIP_DIR}" ]]; then
       mkdir -p "${WANIP_DIR}"

wanchecker@.service → wanchecker.service

@@ -1,9 +1,9 @@
-# Should be placed to /usr/lib/systemd/user/
+# Should be placed to /usr/lib/systemd/system/
 
 [Unit]
 Description=WAN IPv4 checker & email sender for dynamic IPv4 server environments
 After=network-online.target
 
 [Service]
-User=%i
-ExecStart=/usr/bin/bash /home/%i/wanchecker.sh
+User=mail
+ExecStart=/usr/bin/bash /etc/ssmtp/wanchecker.sh

wanchecker@.timer → wanchecker.timer

@@ -1,4 +1,4 @@
-# Should be placed to /usr/lib/systemd/user/
+# Should be placed to /usr/lib/systemd/system/
 
 # https://wiki.archlinux.org/index.php/Systemd/Timers