Convert pwdLastSet to a human readable date

Here it is a simple (and a bit hacky, I know) one-liner for bash shell (even under Windows if you are using Cygwin) to convert the cryptic pwdLastSet timestamp of Active Directory (which represent when a user has changed the last time his/her AD password)


D=128457325992343750; date -d "01/01/1601 UTC $(let D=D/10000000; echo $D) seconds"

where the very large number after the first D= it’s your pwdLastSet value. This strange timestamp it’s a 1/100 of a nanosecond (so, it’s 1/10^7 seconds) and the ticks are counted from January 1st, 1601. Don’t ask me why, probably they didn’t like the Epoch time :)

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Disable directory listing in Apache with Debian

If you find one of your servers with the ugly directory listing enabled, there’s a quick way to disable it in Debian

# echo autoindex | a2dismod
# /etc/init.d/apache2 restart

For other Apache installations in other distro, you can simple find the Autoindex option in your config file and delete it manually, then restart Apache

EDIT: a cleaner and more elegant way to achieve the same is, as the comments section says

# a2dismod autoindex

thanks :)

ssh host completion in bash with a predifined user

If you use a lot ssh from your workstation to connect to many servers using the same user (for example, err… root, or a standard user present in every of your servers) as I do, this is a must-have :)

First of all, ensure you have

HashKnownHosts no

in your ssh_config.

Then, edit your .bashrc and append these lines:

complete -r ssh
_cssh ()
{
cur=${COMP_WORDS[COMP_CWORD]};
COMPREPLY=($(compgen -W "$(cat ${HOME}/.ssh/known_hosts |awk -F ',' '{print $1}')" -- ${cur##root@}))
}
complete -P "root@" -F _cssh ssh

you can change the root@ with your user@.

Enjoy!

pbzip2: parallel bzipping

Probably this software existed for a quite long time but I didn’t know its existence ’til now: pbzip2
it’s basically a bzip2 algorithm implementation with pthreads support. This mean, in a always more SMP world, that you can greatly improve your bzipping perfomances (divide the zipping time by the number of cores you have et voilĂ !)

Compression syntax is totally compatible:

$ pbzip2 big.file

while to unzip you have to do

$ pbzip2 -d big.file.bz2

Use with caution (or with -l and -p switches) cause you can easily saturate your 4xSix-cores monster.

MySQL slaves and the “corrupted” relay log/binlog problem

When trying to pull up to date a new slave, maybe using a binlog server (a MySQL server with no true tablespace, just acting as master for slaves, feeding them with replication data), you may encounter an error like this in your mysql.err file, after noticing the replication has just broken

091028 11:32:49 [ERROR] Slave SQL: Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log), a network problem, or a bug in the master's or slave's MySQL code. If you want to check the master's binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave. Error_code: 1594
091028 11:32:49 [Warning] Slave: Field 'owner' doesn't have a default value Error_code: 1364
091028 11:32:49 [ERROR] Error running query, slave SQL thread aborted. Fix the problem, and restart the slave SQL thread with "SLAVE START". We stopped at log 'mysqld-bin.000780' position 786513508

Well, everything on the web points to a “OMG, my file is corrupt!! My disk is freaking out!”. Probably, instead, it’s just simpler: you have forgotten a FLUSH LOGS; before backing up your binary logs from the original master. So, when you are recreating the binlog server from the backup, the final slave arrives to the last statement wich obviously is not complete/correct and booom, it stops.

The solution is to copy the correct and complete binlog file (in my case mysqld-bin.000780) again in the binlog server, then issue a
STOP SLAVE;
CHANGE MASTER TO master_log_file="mysqld-bin.000780", master_log_pos=786513508;
SLAVE START;

and… problem solved!
(remember to adjust file name and position to suite your needs)

Lesson learned (once again): always test your backups and do not hesitate to flush with MySQL :)

Using tee to redirect output to multiple programs

Via http://linux.byexamples.com/archives/144/redirect-output-to-multiple-processes/

You already know that if you want to pass the output of a program to the input of another program, you can use the pipe | character.

You now that if you want to write the ouput of a program to the disk and at the same time pass it as input to another program, you can use tee.

But maybe you don’t know that if you want to pass the ouput of a program to multiple programs as input, you can use tee again with a little of subshelling.

# source_program | tee (> program1) (> program2) (> programN)| programN+1