SSH Notes [KPTree Wiki]

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{{tag>linux debian ssh "ssh notes"}}
======SSH Notes======

=====SSH Login Message=====
====Acronyms and Definitions====
  *MOTD = Message of the Day

====Login Messages====
  *''sudo vim /etc/issue.net'' Displays a message before the user begins login, I do not use this.
    *''sudo vim /etc/ssh/sshd_config'' ensure the following option is set ''Banner /etc/issue.net'' (you can actually used any path/file)
    *''sudo systemctl reload sshd'' needs to be performed after any change to the configuration file to activate the changes.
  *''sudo vim /etc/motd'' Displays the banner text after login. This usually has some predefined Linux distribution text

====Login Scripts====
====Debian====
  *''ls -la /etc/update-motd.d/'' to see the scripts that are run after the MOTD is displayed.
The Debian script is very simple: 
<code bash>
#!/bin/sh
uname -snrvm
</code>

====Ubuntu====
Ubuntu has multiple scripts some that I like and some that I do not like.  
This system status information script, ++++/etc/update-motd.d/50-landscape-sysinfo|
<code>
#!/bin/sh
# pam_motd does not carry the environment
[ -f /etc/default/locale ] && . /etc/default/locale
export LANG
cores=$(grep -c ^processor /proc/cpuinfo 2>/dev/null)
[ "$cores" -eq "0" ] && cores=1
threshold="${cores:-1}.0"
if [ $(echo "`cut -f1 -d ' ' /proc/loadavg` < $threshold" | bc) -eq 1 ]; then
    echo
    echo -n "  System information as of "
    /bin/date
    echo
    /usr/bin/landscape-sysinfo
else
    echo
    echo " System information disabled due to load higher than $threshold"
fi</code>
++++
The main information script is written in python3, ++++/usr/bin/landscape-systeminfo|
<code>
#!/usr/bin/python3
import sys, os

try:
    if os.path.dirname(os.path.abspath(sys.argv[0])) == os.path.abspath("scripts"):
        sys.path.insert(0, "./")
    else:
        from landscape.lib.warning import hide_warnings
        hide_warnings()

    from twisted.internet import reactor

    from landscape.sysinfo.deployment import run
except ImportError:
    # For some reasons the libraries are not importable for now. We are
    # probably during an upgrade procedure, so let's exit, expecting the
    # dependencies to be fixed at next run.
    sys.exit(2)


if __name__ == "__main__":
    run(sys.argv[1:], reactor)

</code>
  *If twisted not installed, ''pip install twisted'' to install
  *if cpuinfo not installed, ''pip install py-cpuinfo'' to install
++++

====Python Code====
++++python3 agnostic code | 
<code>
#!/usr/bin/python3

import psutil
import platform
from datetime import datetime
import cpuinfo
import socket
import uuid
import re

def get_size(bytes, suffix="B"):
    """
    Scale bytes to its proper format
    e.g:
        1253656 => '1.20MB'
        1253656678 => '1.17GB'
    """
    factor = 1024
    for unit in ["", "K", "M", "G", "T", "P"]:
        if bytes < factor:
            return f"{bytes:.2f}{unit}{suffix}"
        bytes /= factor

def System_information():
    print("="*40, "System Information", "="*40)
    uname = platform.uname()
    print(f"System: {uname.system}")
    print(f"Node Name: {uname.node}")
    print(f"Release: {uname.release}")
    print(f"Version: {uname.version}")
    print(f"Machine: {uname.machine}")
    print(f"Processor: {uname.processor}")
    print(f"Processor: {cpuinfo.get_cpu_info()['brand_raw']}")
    print(f"Ip-Address: {socket.gethostbyname(socket.gethostname())}")
    print(f"Mac-Address: {':'.join(re.findall('..', '%012x' % uuid.getnode()))}")

    # Boot Time
    print("="*40, "Boot Time", "="*40)
    boot_time_timestamp = psutil.boot_time()
    bt = datetime.fromtimestamp(boot_time_timestamp)
    print(f"Boot Time: {bt.year}/{bt.month}/{bt.day} {bt.hour}:{bt.minute}:{bt.second}")

    # print CPU information
    print("="*40, "CPU Info", "="*40)
    # number of cores
    print("Physical cores:", psutil.cpu_count(logical=False))
    print("Total cores:", psutil.cpu_count(logical=True))
    # CPU frequencies
    cpufreq = psutil.cpu_freq()
    print(f"Max Frequency: {cpufreq.max:.2f}Mhz")
    print(f"Min Frequency: {cpufreq.min:.2f}Mhz")
    print(f"Current Frequency: {cpufreq.current:.2f}Mhz")
    # CPU usage
    print("CPU Usage Per Core:")
    for i, percentage in enumerate(psutil.cpu_percent(percpu=True, interval=1)):
        print(f"Core {i}: {percentage}%")
    print(f"Total CPU Usage: {psutil.cpu_percent()}%")

    # Memory Information
    print("="*40, "Memory Information", "="*40)
    # get the memory details
    svmem = psutil.virtual_memory()
    print(f"Total: {get_size(svmem.total)}")
    print(f"Available: {get_size(svmem.available)}")
    print(f"Used: {get_size(svmem.used)}")
    print(f"Percentage: {svmem.percent}%")

    print("="*20, "SWAP", "="*20)
    # get the swap memory details (if exists)
    swap = psutil.swap_memory()
    print(f"Total: {get_size(swap.total)}")
    print(f"Free: {get_size(swap.free)}")
    print(f"Used: {get_size(swap.used)}")
    print(f"Percentage: {swap.percent}%")

    # Disk Information
    print("="*40, "Disk Information", "="*40)
    print("Partitions and Usage:")
    # get all disk partitions
    partitions = psutil.disk_partitions()
    for partition in partitions:
        print(f"=== Device: {partition.device} ===")
        print(f"  Mountpoint: {partition.mountpoint}")
        print(f"  File system type: {partition.fstype}")
        try:
            partition_usage = psutil.disk_usage(partition.mountpoint)
        except PermissionError:
            # this can be catched due to the disk that
            # isn't ready
            continue
        print(f"  Total Size: {get_size(partition_usage.total)}")
        print(f"  Used: {get_size(partition_usage.used)}")
        print(f"  Free: {get_size(partition_usage.free)}")
        print(f"  Percentage: {partition_usage.percent}%")
    # get IO statistics since boot
    disk_io = psutil.disk_io_counters()
    print(f"Total read: {get_size(disk_io.read_bytes)}")
    print(f"Total write: {get_size(disk_io.write_bytes)}")

    ## Network information
    print("="*40, "Network Information", "="*40)
    ## get all network interfaces (virtual and physical)
    if_addrs = psutil.net_if_addrs()
    for interface_name, interface_addresses in if_addrs.items():
        for address in interface_addresses:
            print(f"=== Interface: {interface_name} ===")
            if str(address.family) == 'AddressFamily.AF_INET':
                print(f"  IP Address: {address.address}")
                print(f"  Netmask: {address.netmask}")
                print(f"  Broadcast IP: {address.broadcast}")
            elif str(address.family) == 'AddressFamily.AF_PACKET':
                print(f"  MAC Address: {address.address}")
                print(f"  Netmask: {address.netmask}")
                print(f"  Broadcast MAC: {address.broadcast}")
    ##get IO statistics since boot
    net_io = psutil.net_io_counters()
    print(f"Total Bytes Sent: {get_size(net_io.bytes_sent)}")
    print(f"Total Bytes Received: {get_size(net_io.bytes_recv)}")

if __name__ == "__main__":

    System_information()
</code>
++++

====Some Links:====
  *[[How to manage SSH login message|https://www.simplified.guide/ssh/suppress-banner]]
  *[[HowTo: Set a Warning Message (Banner) in SSH|https://www.shellhacks.com/setup-warning-message-banner-ssh/]]
  *[[Protect SSH Logins with SSH & MOTD Banner Messages|https://www.tecmint.com/protect-ssh-logins-with-ssh-motd-banner-messages/]]

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