After installing Apache 2.2.3 on Centos 5.5, adding virtual domains with Directory indexes will not be possible and the apache welcome page will be displayed if there isn't an index file in the root directory of the vhost.



This behavior can be fixed by editing /etc/httpd/conf.d/welcome.conf and change it from:


to
...

By default on a Debian distro, named daemon listens on all available interfaces. In order to change it to listen on a specific IP address or localhost, edit the named.conf.options

# vim /etc/bind/named.conf.options
options {
directory "/var/cache/bind";

// If there is a firewall between you and nameservers you want
// to talk to, you may need to fix the firewall to allow multiple
// ports to talk. See http://www.kb.cert.org/vuls/id/800113

// forwarders {
// 0.0.0.0;
// ...

Make sure that the filesystem is not exported via NFS (locked by lockd). Stop NFS/portmap services and retry unmounting.

In Linux it is possible to change a user's password with the ouput of an echo command, coming from standard input, via pipe.

NAME
passwd - update a user’s authentication tokens(s)

SYNOPSIS
passwd [-k] [-l] [-u [-f]] [-d] [-n mindays] [-x maxdays] [-w warndays] [-i inactivedays] [-S] [--stdin] [user-
name]

DESCRIPTION
Passwd is used to update a user’s authentication token(s).

Passwd is configured to work through the Linux-PAM API. Essentially, it initializes itself as ...

Linux refresh init process after modifying inittab without reboot

man init

If the shell noclobber environment variable is set, you will not be able to overwrite a file's content by redirecting some output to it.

First option would be to disable the noclobber variable:


The second option is to use the pipe (|)right after the redirection sign:
# echo "2nd Overwritten content" ...

Redirecting standard output/error in a Linux/BSD shell can very easy overwrite a file, removing it's content, making it impossible to recover (unless there's a backup).

To prevent this sh, bash and ksh shells implement an evironment variable called noclobber.

# cat tmp.file
If you use a lot of file redirection in your scripts it's quite easy to overwrite existing files accidentaly.
To prevent this, most shells implement the noclobber environment variable.

# echo "Overwritten content">tmp.file ...

Here are a few tricks for querying Debian's dpkg command.

Upgrade or install a package:


Listing installed packages in Debian. You can use directly package name after '-l' if you know it's name.:

# dpkg -l
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name Version Description
+++-============================================-============================-============================================
ii acl 2.2.47-3 Access control list utilities
ii acpi 1.4-2 displays information on ACPI devices
ii acpi-support-base 0.123-1 scripts for handling base ...

Installing and PXE booting RHEL 5 over the network

In the past weeks I needed to install Red Hat Enterprise 5 on two remote HP DL385 blades (if I remember correctly) and I had no one in the datacenter to insert the DVD in the drives. So the situation needed a network installation using PXE booting (Pre-boog eXecution Environment).

Since this was my first encounter with PXE booting and network installations on Linux Google ...