File System size monitoring with shell script

 Schedule this with crontab to run periodically.

#!/bin/sh

#Shell script to monitor the disk space

DBA_EMAIL="email@email.com"
ALERT_THRESHOLD=75
DATE=`date '+%a %b %e %I:%M %p' `
SERVER=`hostname`
df -Pkh | grep -v Filesystem | grep -v tmpfs | grep -v cdrom | grep -v run| awk '{ print $5 " " $6 }' |
while read output;
do
USED_PERCENTAGE=`(echo $output | awk '{ print $1}' | cut -d'%' -f1 )`
PARTITION=`(echo $output | awk '{ print $2 }' )`
if [ $USED_PERCENTAGE -ge $ALERT_THRESHOLD ]; then
echo "Kindly check file-system  \"$PARTITION ($USED_PERCENTAGE %)\" full on $SERVER on $DATE" |
mail -s "Production ALERT_THRESHOLD:- Disk Space Warning \"$PARTITION ($USED_PERCENTAGE %)\" full on $SERVER " $DBA_EMAIL
fi
done

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DSBulk Operation failed with Java heap size

 Example: Operation LOAD_20200714-055402-943439 failed unexpectedly: Java heap space

Increase the Java heap allocation for DSBulk by

export DSBULK_JAVA_OPTS="$DSBULK_JAVA_OPTS -Xmx16G"

Reference: https://docs.datastax.com/en/dsbulk/doc/dsbulk/install/dsbulkInstall.html#Post-installrequirementsandrecommendations

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Install software in Linux with shell scripting

 Below are the examples of installing 'vim' and 'wget' with shell script

vim installation:

Shell script to install software in Linux.
#!/bin/bash
vim --version 1>/dev/null 2>&1
if [[ $? -eq 0 ]]
then
	echo "VIM is already installed"
else
	sudo yum install vim -yum
fi

wget installation:

wget --version 1>/dev/null 2>&1
if [[ $? -eq 0 ]]
then
	echo "WGET is already installed"
else
	sudo yum install wget -yum
fi

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To remove or delete files in Linux when there are more

When there are too many files to delete in a Linux folder, its hard to delete as "rm" won't work directly.

Below is the error message, we get.

$ rm -rf "*.csv"

-bash: /usr/bin/rm: Argument list too long

Resolution:

$ find . -name '*.csv' | xargs rm -v4

This will remove all files which have ".csv" as extension and give verbose output of what it is doing while removing.

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Datastax OpsCenter alerts action codes

 Below is the list of action codes of Datastax Opscenter for reference:

    COMPACTION = 0

    CLEANUP = 1

    REPAIR = 2

    FLUSH = 3

    DRAIN = 4

    DECOMMISSION = 5

    MOVE = 6

    BOOTSTRAP = 7

    STREAMING = 8

    MESSAGES_DROPPED = 9

    GARBAGE_COLLECTION = 10

    CASSANDRA_EXCEPTION = 11

    SNAPSHOT = 12

    NODE_DOWN = 13

    NODE_UP = 14

    NODE_LEFT = 15

    NODE_JOIN = 16

    NODE_MOVE = 17

    OPSC_UP = 18

    OPSC_DOWN = 19

    GC = 20

    REBALANCE = 21

    ALERT = 22

    BACKUP = 23

    CLEAR_SNAPSHOT = 24

    MISC = 25

    NODE_STARTED = 26

    NODE_STOPPED = 27

    NODE_RESTARTED = 28

    PROVISION_CLUSTER = 29

    ROLLING_RESTART = 30

    REMOVE_TOKEN = 31

    ASSASSINATE = 32

    SNAPSHOT_RESTORE = 33

    SET_CONF = 34

    SET_DSE_TYPE = 35

    REPAIR_SERVICE = 36

    BEST_PRACTICE = 37

    CREATE_USER = 38

    UPDATE_USER = 39

    DELETE_USER = 40

    CREATE_ROLE = 41

    UPDATE_ROLE = 42

    DELETE_ROLE = 43

    FAILOVER_DISABLED = 44

    KMIP_ERROR = 46

    TRACE_QUERY = 47

    ALERT_FAILURE = 48

    SYNC_SNAPSHOT = 49

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Auditing file changes in Linux

Enable the audit log for directory /var/log/cassandra on a Cassandra node

Add below rule for the directory to audit, here we are search for deleted files under /var/log/cassandra directory.

sudo vi /etc/audit/rules.d/audit.rules

-a always,exit -F dir=/var/log/cassandra -S unlink -S unlinkat -S rename -S renameat -S rmdir -k delete_var

sudo service auditd restart

Verify rules: sudo auditctl -l

Verify: sudo ausearch -k delete_var

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