Gregory Colpart's blog

Yesterday I installed RT on Apache/mod_perl server with default config in RT_Config.pm file:

Set($Timezone , 'US/Eastern');

I included PerlRequire webmux.pl in its VirtualHost and I discover today that this directive changes timezone for all Apache log files! Weird behavior… and I confirm that this server is hosted in Marseille (France), not in USA ;-)

Migrate applications to MySQL 5 could need some rewrite. Here is one example :

mysql5> SELECT * FROM table0, table1 JOIN table2 on table0.colA = table2.colB;
ERROR 1054 (42S22): Unknown column 'table0.colA' in 'on clause'

That’s because JOIN operator has now higher priority. Previously, this request was interpreted like ((table 0, table1) JOIN table2) and now it is (table 0, (table1 JOIN table2)). A fast fix is adding parenthesis:

mysql5> SELECT * FROM (table0, table1) JOIN table2 on table0.colA = table2.colB;

You can find more information in MYSQL bug #13832 and in MySQL manual (See Join Processing Changes in MySQL 5.0.12 section).

git is the SCM developped for the Linux kernel after the famous affair with proprietary Bitkeeper system. There are good tutorials for git (for example, the official one) and a fun video talk with the “Linus touch”. I’m “yet another victim” of the buzz^Wpopularity of git (particularly in the Debian community):
git://git.debian.org/git/collab-maint/pppoeconf.git

On a mail server, I had a strange problem on ext3 partition. When I saw output of ‘df’ command, partition was Use% at 95% (size of 8 Go) but only 2 Go if I use ‘du’ command. And I have only 15.000 files on this partition according “find | wc -l” hack (then no block-size problem). Solution is in Linux ext3 FAQ :

The standard cause for this is some user process keeping a deleted file open. When this happens, the space is not visible via ‘du’, since the file is no longer visible in the directory tree. However, the space is still used by the file until it is deallocated, and that can only happen once the last process which has the file open either closes its file descriptor to the file, or the process exits. You can use the lsof program to try to find which process is keeping an open file. Usually it’s some log file, or some large data base file which gets rotated out, but some older process are still keeping the log file open.

Then I discovered ghost files with :

# lsof | grep “(deleted)”

In my case, an amavis daemon didn’t close an old and big log file.
I closed this process and now ‘df’ command say me Use% at 20%.

Then ‘df’ command win ;-)
End of alert.

When you are not in your secure hacklab, and you login on your Debian systems (laptop, remote server), it’s not secure to enter your very private password (“please, could you see ceiling” is not a secure way).

Then you could use OTP (One Time Password) way.
On Debian system, do this :

# (apt-get|aptitude) install opie-server

Add pam_opie.so in your PAM info. For example, in pam.d/ssh (or pam.d/common-auth for all your pam.d/foo), modify to have :

auth sufficient pam_unix.so
auth sufficient pam_opie.so
auth required pam_deny.so

Your systeam is now ready for OTP.

To use it, log you and :

$ opiepasswd -f -c
(You must choose a secret pass phrase to generate your OTP)

Generate 10 passwords for example :

$ opiekey -n 10 497 ab1234
(Enter your secret pass phrase)

In this example, 497 is your current seq number and ab1234 is your seed. You could known them with opieinfo command (only if /etc/opiekeys is chmod 644).

Print your 10 passwords (with your printer or you hand if you are paranoiac) and you could use them. For example, OTP login :

homer login : jdoe
Password : [enter]
otp-md5 497 ab1234 ext, Response : [enter your OTP number 497][enter]
Welcome !!
jdoe@homer:~$