Calculate total amount of Physical RAM on all Active TaskTrackers in MR1 using Unix tools

The following should accomplish this assuming the interest is in identifying how much total physical RAM is available on all Active TaskTrackers (i.e. not blacklisted) in MR1 using common Unix commands:

for i in $(curl -s http://jobtracker.company.com:50030/machines.jsp?type=active | grep 'href="http://' | cut -d '=' -f2 | cut -d '"' -f2); do curl -s $i"jmx" | grep  'TotalPhysicalMemorySize' | grep -Po [0-9]+ ; done | paste -sd+ - | bc; 

NOTE:  Replace the http://jobtracker.company.com with the appropriate hostname of the JobTracker.

The above command will retrieve the list of active TaskTrackers from the JobTracker, iterate through the list, summing the 

TotalPhysicalMemorySize

 metric from each TaskTracker's JMX and display the end result, in bytes.

Example output:
[user@node10 ~]$ for i in $(curl -s http://node1.com:50030/machines.jsp?type=active | grep 'href="http://' | cut -d '=' -f2 | cut -d '"' -f2); do curl -s $i"jmx" | grep  'TotalPhysicalMemorySize' | grep -Po [0-9]+ ; done | paste -sd+ - | bc;

23488339968
[user@node10 ~]$



As replied here: https://www.quora.com/How-can-I-check-total-RAM-in-Hadoop-cluster-running-MR1-not-YARN

Collect multiple commands’ output to a single file

Syntax to run a few commands to gather some user / group ID info, as well as recursively list a folder’s contents and permissions all into a single file:

{ grep "^hadoop" /etc/group; id mapred; id hdfs; id mapred; id yarn; ls -ltrRa /var/log/hadoop-0.20-mapreduce/ } > /tmp/`hostname`-mr-info.txt


grep “^hadoop” /etc/group = list the accounts that are associated with the group hadoop
id mapred = display account ID info about the user mapred
id hdfs = display account ID info about the user hdfs
id yarn = display account ID info about the user yarn
ls -ltrRa /var/log/hadoop-0.20-mapreduce/ = Provide a recursive (-R) long list (-l)  of all (-a) directory and files from /var/log/hadoop-0.20-mapreduce, that’s sorted based on file timestamp (-t) in reverse order (-r)

{ ; } > /tmp/`hostname`-mr-info.txt  =   Run the commands first within the curly braces { }, then provide all the output to a file called (hostname of the machine)-mr-info.txt.  Important to have the final semicolon before terminating the end (right-most) curly brace otherwise a piping error will result.