Using Find output and making a grep on it

Some times, we may be in situation to find the list of files in a recursive directory and search for a specific contents in it.

Below is the command which does that. In below command I'm trying to find commons-beanutils.jar recursive in a directory and a grep command on the listed files to actually find do the jar files has class file 'BeanUtilsBean.class in it.

find . -name *beanutils*.jar -exec grep 'BeanUtilsBean.class' '{}' \;

How to view and change the timestamp of a file say creation date

'stat' command will give the last-accessed/last-modified/file-created date with timestamps in it.

[prakashc@cu120 jbossweb-tomcat50.sar]$ stat commons-beanutils-1.8.0.jar
File: `commons-beanutils-1.8.0.jar'
Size: 231320 Blocks: 464 IO Block: 4096 regular file
Device: 303h/771d Inode: 6547316 Links: 1
Access: (0700/-rwx------) Uid: ( 7069/prakashc) Gid: ( 4001/__cubitu)
Access: 2011-02-09 07:01:55.000000000 +0530
Modify: 2011-02-09 05:50:40.000000000 +0530
Change: 2011-02-09 06:12:08.000000000 +0530

using 'touch' command you can modify the date created

touch commons-beanutils-1.8.0.jar -t [[CC]YY]MMDDhhmm [.SS]

MM - The month of the year [01-12].
DD - The day of the month [01-31].
hh - The hour of the day [00-23].
mm - The minute of the hour [00-59].
CC - The first two digits of the year.
YY - The second two digits of the year.
SS - The second of the minute [00-61].

Remove duplicate rows from postgress using ctid

Today, I was in a situation to delete the duplicate row entries in a table which has all the column values similar including the unique constraints too.

I'm not sure how the table accepted the unique constraints of same value, it's been an large dataset and I guess some could've gone wrong on migration or some thing else.

While trying to reindex the table it failed stating

>>

reindexdb: reindexing of database "testdb" failed: ERROR: could not create unique index "folder_pk"

DETAIL: Table contains duplicated values.

<<


After trying to remove the duplicate values, I found all the columns values are similar including the primary keys,

So finally got an idea from one forum, which suggests to use the "ctid" of the rows to delete that.

It looks, for the table rows, internally there is ctid and you can view it using

select ctid, id from table;

Then, remove the specific rows which you need using the ctid.

"Lockness" eclipse thread dump analysis plugin

There is a eclipse plugin "Lockness" for thread dump analysis (http://lockness.plugin.free.fr/setup.php). Using this we can analyze the thread locks to diagonalize the problems. To download (http://lockness.plugin.free.fr/archive/com.cr.lockness.Lockness_3.0.0.jar), put this jar to eclipse3.x/plugins dir and restart eclipse.

How to take a thread dump:

Sending "kill -3 signal to the JBOSS/TOMCAT process" will give you the whole thread dump. Ex: kill -3 #### -> process id.

After executing the above command, you can find thread dump in catalina.out for tomcat or server.log for jboss.

You've to trim the thread dump contents exactly from above log files, such that the dump file starts with "Full thread dump" and end with "VM Thread".

Also, if you have some timestamps added in thread dump, you can trim that using below cut command. For ex: say each line has some time stamps added like "2010-10-25 13:29:23 PDT", then to skip the first 3 columns. Use below command

cat threaddump.txt | cut -d " " -f4- > cut_file_threaddump.txt

The above command will skip first 3 columns and saves rest of the columns what we needed to cut_file_threaddump.txt.

Then from eclipse, create a new java project, create folder pointing to above create dump dir and opening this using "Lockness" thread dump analyser plugin will give you the analysis.

How to redirect ports inside same machine using IPTABLES

As my mail server is running on port 8056, I got ended up searching to find a way to redirect all the mails which comes to port25 to port8056.

Below is one way of doing which helped me using iptables entry.


sudo iptables -t nat -A OUTPUT -p tcp -d 127.0.0.0/8 --dport 25 -j REDIRECT --to-port 8056
sudo iptables -t nat -A OUTPUT -p tcp -d x.x.x.x --dport 25 -j REDIRECT --to-port 8056
sudo iptables -t nat -A PREROUTING -p tcp --dport 25 -j REDIRECT --to-ports 8056


In the above commands

command 1 is to, forward port25 requests to port 8056 which are initiated via localhost. (i.e) telnet localhost 25.
command 2 is to, forward port25 requests to port 8056 which are initiated via IP address. (i.e) telnet x.x.x.x 25.
command 3 is to, forward the other network m/c requests to port 8056 through port25.