go-motd

Introduction

This project was inspired by RIKRUS's and Hermann Björgvin's MOTD scripts.

I've decided to use Go because it is about 10x faster than a similar bash script and it makes for a great first project using the language. In my tests it typically runs in 10-20ms, a similar bash script takes 200-500ms.

The available information will depend on the user privileges, you will need to be able to run (without sudo) systemctl status, docker ps and zpool status for example.

Note that the BTRFS and ZFS space statistics are totals, that is to say, a RAID5 setup shows the used/total space across all drives. For example 3x4TB disks in RAIDZ1 show 10.91TB total, not the usable space which is about 7TB.

You can dump the default config by passing an invalid path as the -c/--config argument and using --dump-config at the same time.

Configuration changed on 2020-05-29, automatic conversion can be done with migrate.go. TL;DR of changes:

• global section instead of being root level
• header and content are now pad_header and pad_content
• failedOnly is now warnings_only, I think this more clearly communicates what it does
• All keys changed from camelCase to snake_case, follows yaml standards better

Example

All OK

With some warnings

Requirements

• Kernel 5.6+ (drivetemp module) or hddtemp daemon are required for disk temps
• dockerMinAPI in docker.go might need tweaking
• zfs-utils for zpool status
• go-check-updates for updates
• lm_sensors for CPU temperatures

Installation

Arch Linux

wget https://raw.githubusercontent.com/cosandr/go-motd/master/PKGBUILD
makepkg -si

go-motd will use the config file in /etc/go-motd/config.yaml.

Generic

# Clone repository and cd to it
git clone https://github.com/cosandr/go-motd
cd go-motd
## Manual installation
go mod vendor
go build -a -ldflags "-X main.defaultCfgPath=/etc/go-motd/config.yaml"
# Generate default config
sudo ./go-motd --config /dev/null --dump-config > "default-config.yaml" 2> /dev/null
# Install binary
sudo install -m 755 go-motd /usr/bin/
## Using setup.sh
sudo ./setup.sh install

Running

Two modes of operations, running directly or as a daemon writing to a file at fixed intervals and triggered by SIGHUP.

Direct run at login

Assuming it was installed as outlined above, just run the binary by adding go-motd in your shell rc file.

Daemon mode

Recommended usage is running with systemd and pointing go-motd at /etc/motd.

[Unit]
Description=Go MOTD generator

[Service]
PIDFile=/run/go-motd.pid
ExecReload=/usr/bin/kill -s HUP $MAINPID
ExecStart=/usr/bin/go-motd --daemon --pid /run/go-motd.pid --output /etc/motd

If it's not showing up, you can add [[ -s /etc/motd ]] && cat /etc/motd to your shell rc file.

A refresh can be forced by issuing a SIGHUP to the process, either with systemctl reload go-motd.service or kill -HUP $(cat /run/go-motd.pid)

Configuration

Global

• warnings_only will hide content unless there is a warning, per-module override available
• show_order list of enabled modules, they will be displayed in the same order. If not defined, the order in defaultOrder will be used.
• col_def arrange module output in columns as defined by a 2-dimensional array, configuration for example pictures shown below. Note that this overrides show_order.

col_def:
  - [sysinfo]
  - [updates]
  - [docker, podman]
  - [systemd]
  - [cpu, disk]
  - [zfs]
  - [btrfs]

• col_pad number of spaces between columns

Generic options

All modules implement at least warnings_only, pad_header and pad_content.

• warnings_only overrides global setting for that module only
• pad_header is a 2-element array of integers, the first represents the number of spaces before the text, the second is spaces after the text, but before :

# pad_header: [0, 2]
Example  : OK
# pad_header: [2, 0]
  Example: OK
# pad_header: [1, 2]
 Example  : OK

• pad_content is the same but for details, the padding applies to all lines equally

CPU temperatures

• warn/crit are temperatures to consider warning or critical level
• use_exec get CPU temperature by parsing sensors -j output

Disk temperatures

• warn/crit are temperatures to consider warning or critical level
• ignore list of disks to ignore (uses names from /dev/)
• use_sys will get disk temperatures from /sys/block instead of the hddtemp daemon. The drivetemp kernel module is required.

Disk usage (BTRFS/ZFS)

• warn/crit percentage of disk space used before it is considered a warning or critical level, default is 70% and 90% respectively

BTRFS

• show_free show free space instead of used
• use_exec get BTRFS filesystem info by parsing btrfs filesystem usage --raw
• sudo use sudo btrfs commands, required for accurate RAID56 data
• btrfs_cmd override btrfs command, useful for wrapper scripts. For example:

# visudo -f /etc/sudoers.d/btrfs-us
andrei ALL=(root) NOPASSWD: /usr/bin/btrfs-us
# cat /usr/bin/btrfs-us
#!/bin/sh

btrfs filesystem usage $@

Docker

• ignore list of ignored container names
• use_exec get containers by parsing docker command output

Podman

• ignore list of ignored container names
• sudo get root containers, you should be able to run sudo podman without a password
• include_sudo includes both root and rootless containers

System information

No extra config

Systemd

• units list of monitored units, must include file extension. This option must be set for the module to work.
• hide_ext hide the unit file extension when displaying their status
• inactive_ok consider inactive units with exit code 0 as being OK, if false they will be considered warnings
• show_failed display all failed units, similar to systemctl --failed

Updates

• show displays the list of pending updates
• short_names use short names for time values (1h5m instead of 1 hour, 5 min)
• address listen address of go-check-updates, can be unix socket
• every request cache update if it is older than this duration
• file path to go-check-updates output json, setting this will not use the API at all

Adding more modules

Basic datasources/example.go

package datasources

import "github.com/cosandr/go-motd/utils"

// These must not occur in the output string itself, if they do, feel free to use your own constants
const (
  examplePadL = "^"  // Default is ^L^
  examplePadR = "&"  // Default is ^R^
)

// Optional, can use ConfBase or ConfBaseWarn
// Recommended to use a struct, even if it only contains one of the base configs
type ConfExample struct {
  ConfBase `yaml:",inline"`
  More bool `yaml:"more"`
}

// Init is mandatory
func (c *ConfExample) Init() {
    // Base init must be called
    c.ConfBase.Init()
    // Can change default padding here
    // Set right padding for header to 2 spaces
    c.PadHeader[1] = 2
    // Set other defaults
    c.More = true
    // Custom padding strings
    c.padL = "^"
    c.padR = "&"
}


func GetExample(ch chan<- SourceReturn, conf *Conf) {
	c := conf.Example
	// Optional, but recommended if you use WarnOnly
	// Check for warnOnly override
	if c.WarnOnly == nil {
		c.WarnOnly = &conf.WarnOnly
	}
	sr := NewSourceReturn(conf.debug)
	defer func() {
		ch <- sr.Return(&c.ConfBase)
	}()
    sr.Header, sr.Content, sr.Error = internalFunc(&c)
    return
}

func internalFunc(c *ConfExample) (header string, content string, err error) {
	// You should return a ModuleNotAvailable error if it is appropriate.
	// Remember to use c.padL/c.padR when preparing header and content
	header = fmt.Sprintf("%s: %s\n", utils.Wrap("Example", c.padL, c.padR), utils.Good("OK"))
	return
}

Update common_vars.go

type Conf struct {
  // Add your type to the Conf struct
  Example ConfExample
}

// Update Init()
func (c *Conf) Init() {
  // Init must be called to avoid likely panic 
  // This is caused by uninitialized padding slices if they are not in the config file
  c.Example.Init()
}

// Add to a case to run your function in RunSources
case "example":
    go GetExample(ch, c)

Modify main.go (optional)

package main

// Add your module to defaultOrder
var defaultOrder = []string{..., "example"}

You may also add an entry to config.yaml, this will override what you have set in Init().