Friday, April 3, 2015

Script to simulate multiple DHCP clients

#!/bin/sh
#simulate 255 IPhones requesting DHCP
 
 
# Apple OUI = D8:96:95
BASE="d8:96:95:08:96"
FROM=$1
shift
TO=$2
 
if [ -e $FROM ]; then FROM=1; fi
if [ -e $TO ]; then TO=1; fi
 
for i in `seq $FROM $TO`
do
    LSB=`echo "obase=16; $i" | bc`
    MAC="$BASE:$LSB"
    HNAME="`uname -n`-fakehost-$i"
    #CMD="$HOME/bin/dhtest -m $MAC -V -i eth1 -h '$HNAME'"
    CMD="$HOME/bin/dhtest -m $MAC -i eth1 -h '$HNAME'"
    echo $CMD
    $CMD
    sleep 1
done

Another way, the program dhtest (source code) can be download from  https://github.com/saravana815/dhtest.  

For example:
 
git clone https://github.com/saravana815/dhtest
cd dhtest
make

Daily backup of local git changes

While working on a ticket and not ready to commit, it's a good idea to backup all of our changes to an archive file.

The following script does all that and executed daily by cronjob automatically.
  1. create a file, say "backup" in /etc/cron.daily
  2. Type the following (change '<yourhome directory>' to your own login name and <git location> to the git directory where source codes are located):
backing up changed files to tarball
#!/bin/sh
pushd <your source-code location>
LIST=`git status --porcelain | sed -n -e '/^ [D|M]/p' | sed -e 's/^ [D|M] //'`
backupname=`git branch | sed -n -e "/^* /p" | sed  -e 's/** //'`
backupname=$backupname-`date "+%s"`.backup.tar.bz2
dest='<your home directory>'
if [ ! -d "$dest" ]
then
    mkdir -p $dest
fi
tar jcvf $dest/$backupname $LIST > /dev/null

Make the file executable:
chmod +x /etc/cron.daily/backup