indicator-SysMonitor

Indicator-SysMonitor does a little, but does it well. Once installed and run, it displays CPU and RAM usage on your top panel. Simple.

Download from here

Conky

One of my personal favourites

Screenlet you’ll find a bunch of differently styled CPU and RAM monitors included in the screenlets-all package available in the Ubuntu Software Center.

Glances

To install:

sudo apt-get install python-pip build-essential python-dev
sudo pip install Glances
sudo pip install PySensors

VMSTAT

Displays information about CPU, memory, processes, etc.

IOSTAT

This command line tool will display statistics about your CPU, I/O information for your hard disk partitions, Network File System (NFS), etc. To install iostat, run this command:

sudo apt-get install sysstat

To start the report, run this command:

iostat

To check only CPU statistics, use this command:

iostat -c

For more parameters, use this command:

iostat --help

MPSTAT

The mpstat command line utility will display average CPU usage per processor. To run it, use simply this command:

mpstat

For CPU usage per processor, use this command:

mpstat -P ALL

Saidar

Saidar also allows to monitor system device activities via the command line.

You can install is with this command:

sudo apt-get install saidar

To start monitoring, run this command:

saidar -c -d 1

Stats will be refreshed every second.

GKrellM

GKrellM is a customizable widget with various themes that displays on your desktop system device information (CPU, temperature, memory, network, etc.).

To install GKrellM, run this command:

sudo apt-get install gkrellm

Monitorix

Monitorix is another application with a web-based user interface for monitoring system devices.

Install it with these commands:

sudo add-apt-repository ppa:upubuntu-com/ppa
sudo apt-get update
sudo apt-get install monitorix

Start Monitorix via this URL:

http://localhost/monitorix/

Following are the tools for monitoring a linux system

1. System commands like top, free -m, vmstat, iostat, iotop, sar, netstat etc. Nothing comes near these linux utility when you are debugging a problem. These command give you a clear picture that is going inside your server
2. SeaLion: Agent executes all the commands mentioned in #1 (also user defined) and outputs of these commands can be accessed in a beautiful web interface. This tool comes handy when you are debugging across hundreds of servers as installation is clear simple. And its FREE
3. Nagios: It is the mother of all monitoring/alerting tools. It is very much customization but very much difficult to setup for beginners. There are sets of tools called nagios plugins that covers pretty much all important Linux metrics
4. Munin
5. Server density: A cloudbased paid service that collects important Linux metrics and gives users ability to write own plugins.
6. New Relic: Another well know hosted monitoring service.
7. Zabbix

For the last few years I have used:

System Load Indicator

available from Software Centre

top

top is monitoring Software, listing all the processes with CPU/RAM usage, Overall CPU/RAM usage and more Also it's mostly installed by default

htop

htop is like an extended version of top. It has all the features from above, but you can see child processes and customize the display of everything. It also has colors.

iotop

iotop is specifically for Monitoring Hard rive I/O It lists all processes and shows their Hard drive usage for read and write.

You might want to try sysmon. Although not as fancy as Glances, it is very straightforward and easy to use.

If you want to get dirty and do a little scripting in python, here are some basics of system monitoring with Python to get you started.

You'll need an external module called psutil to monitor most things. It's easiest to use an external module installer instead of building from source.

Note: These examples are written in Python 2.7

sudo apt-get install pip
sudo pip install psutil

Now that we have the modules installed, we can start coding.

First, create a file called usage.py.

gedit ~/usage.py

Start by importing psutil

import psutil

Then, create a function to monitor the percentage your CPU cores are running at.

def cpu_perc(): 

    cpu_perc = psutil.cpu_percent(interval=1, percpu=True) 
    for i in range(len(cpu_perc)):
        print "CPU Core", str(i+1),":", str(cpu_perc[i]), "%"

Let's break that down a bit, shall we?

The first line, cpu_num = psutil.cpu_percent(interval=1, percpu=True), finds the percentage that the cores in your CPU are running at and assigns it to a list called cpu_perc.

This loop right here

for i in range(len(cpu_num)):
    print "CPU Core", str(i+1),":", str(cpu_perc[i]), "%"

is a for loop that prints out the current percentage of each of your CPU cores.

Let's add the RAM usage.

Create a function called ram_perc.

def ram_perc():
    mem = psutil.virtual_memory()
    mem_perc = mem.percent
    print "RAM: ", mem_perc, "%"

psutil.virtual_memory gives a data set containing different facts about the RAM in your computer.

Next, you can add some facts about your network.

def net():
    net = psutil.net_io_counters()
    mbytes_sent = float(net.bytes_sent) / 1048576
    mbytes_recv = float(net.bytes_recv) / 1048576
    print "MB sent: ", mbytes_sent
    print "MB received: ", mbytes_recv

Since psutil.net_io_counters() only gives us information about packets sent and received in bytes, some converting was necessary.

To get some information about swap space, add this function.

def swap_perc():
    swap = psutil.swap_memory()
    swap_perc = swap.percent

This one is pretty straightforward.

Temperature is kind of hard to do, so you may need to do some research of your own to figure out what will work with your hardware. You will have to display the contents of a certain file.

Disk usage is a lot easier than temperature. All you need to do is to pass the disk you want to monitor (i.e: /) through a certain function.

def disks():
    if len(sys.argv) > 1:
        for disk in range(1, len(sys.argv)):
            tmp = psutil.disk_usage(sys.argv[disk])
            print sys.argv[disk], "\n"
            print "Megabytes total: ",
            print str(float(tmp.total) / 1048576)
            print "Megabytes used: ",
            print str(float(tmp.used) / 1048576)
            print "Megabytes free: ",
            print str(float(tmp.free) / 1048576)
            print "Percentage used: ",
            print tmp.percent, "\n"

The original output of psutil.disk_usage is this,

>>>psutil.disk_usage('/')
sdiskusage(total=21378641920, used=4809781248, free=15482871808, percent=22.5)

but you can also just receive total, used, free, or percent.

The completed program: (the aforementioned functions were combined)

import psutil, os, sys
mem_perc = 0 #init var
swap_perc = 0 #init var
mbytes_sent = 0 #init var
mbytes_recv = 0 #init var
cpu_perc = 0 #init var
swap = 0 #init var
mem = 0 #init var
net = 0 #init var



def disp(degree):
    global cpu_perc
    global swap
    global swap_perc
    global mem
    global mem_perc
    global net
    global mbytes_sent
    global mbytes_recv

    cpu_perc = psutil.cpu_percent(interval=1, percpu=True)
    swap = psutil.swap_memory()
    swap_perc = swap.percent
    mem = psutil.virtual_memory()
    mem_perc = mem.percent
    net = psutil.net_io_counters()
    mbytes_sent = float(net.bytes_sent) / 1048576
    mbytes_recv = float(net.bytes_recv) / 1048576

    os.system('clear') #clear the screen

    print "-"*30
    print "CPU"
    print "-"*30
    print "CPU Temperature: " , degree, "'C"
    for i in range(len(cpu_perc)):
        print "CPU Core", str(i+1),":", str(cpu_perc[i]), "%"

    print "-"*30
    print "MEMORY"
    print "-"*30
    print "RAM: ", mem_perc, "%"
    print "Swap: ", swap_perc, "%"
    print "-"*30
    print "NETWORK"
    print "-"*30
    print "MB sent: ", mbytes_sent
    print "MB received: ", mbytes_recv
    print "-"*30
    print "DISKS"
    print "-"*30

    if len(sys.argv) > 1:
        for disk in range(1, len(sys.argv)):
            tmp = psutil.disk_usage(sys.argv[disk])
            print sys.argv[disk], "\n"
            print "Megabytes total: ",
            print str(float(tmp.total) / 1048576)
            print "Megabytes used: ",
            print str(float(tmp.used) / 1048576)
            print "Megabytes free: ",
            print str(float(tmp.free) / 1048576)
            print "Percentage used: ",
            print tmp.percent, "\n"

def main():
    print("Press Ctrl+C to exit")
    while True:
        temp = open("/sys/class/thermal/thermal_zone0/temp").read().strip().lstrip('temperature :').rstrip(' C')
        temp = float(temp) / 1000
        disp(temp)

main()

The line temp = open("/sys/class/thermal/thermal_zone0/temp").read().strip().lstrip('temperature :').rstrip(' C') might not work with your hardware configuration.

Run this program from the command line. Pass the disks you want to monitor as arguments from the command line.

$ python usage.py /

Press Ctrl+C to exit

------------------------------
CPU
------------------------------
CPU Temperature:  39.0 'C
CPU Core 1 : 4.8 %
CPU Core 2 : 1.0 %
CPU Core 3 : 0.0 %
CPU Core 4 : 4.9 %
------------------------------
MEMORY
------------------------------
RAM:  33.6 %
Swap:  6.4 %
------------------------------
NETWORK
------------------------------
MB sent:  2.93382358551
MB received:  17.2131490707
------------------------------
DISKS
------------------------------
/ 

Megabytes total:  13952.484375
Megabytes used:  8542.6640625
Megabytes free:  4678.5703125
Percentage used:  61.2 

/media/calvin/Data 

Megabytes total:  326810.996094
Megabytes used:  57536.953125
Megabytes free:  269274.042969
Percentage used:  17.6 

Hope this helps! Comment if you have any questions.

https://github.com/calthecoder/sysmon-1.0.1

Package systat has a tool called sar that does all you want. It can also gather historical data so you can see what happened some time ago.

SeaLion can be handy tool as it has built-in commands to monitor your server performance as well as you can add your own custom commands, scirpts and log output. It's very easy to setup and find out what went wrong at specific time.

1. The free command is the most simple and easy to use command to check memory usage on linux/ubuntu.

   free -m
   

2. To check memory usage is to read the /proc/meminfo file.

   cat /proc/meminfo
   

3. The vmstat command with the s option.

   vmstat -s
   

4. The top command is generally used to check memory and cpu usage per process.

   top
   

5. The htop command also shows memory usage along with various other details.

   htop
   

6. To find out hardware information about the installed RAM.

   sudo dmidecode -t 17
   

I like to use conky which can be configured anyway you like:

You can google conky and find 787,000 hits. There is something for everyone.

At the top of the display notice "Lock screen: 4 Minutes Brightness: 2074". These are generated by "Indicator-Sysmonitor" which allows you to display on the systray / application indicator using a bash script.

For a tutorial on setting up "Indicator-Sysmonitor" see: Can BASH display in systray as application indicator?