Lik`s forum

Members of dmraid arrays (block and software RAID devices) contain metadata signatures which are used to discover/assemble target RAID sets.

To remove them and release undelying block devices one should erase metadata signatures.

Discover all software RAID devices supported on your system, eg:
# dmraid -r
/dev/dm-46: hpt45x, "hpt45x_chidjhaiaa-0", striped, ok, 320172928 sectors, data@ 0
/dev/dm-50: hpt45x, "hpt45x_chidjhaiaa-0", striped, ok, 320172928 sectors, data@ 0
/dev/dm-54: hpt45x, "hpt45x_chidjhaiaa-1", striped, ok, 320172928 sectors, data@ 0
/dev/dm-58: hpt45x, ...

To list all currently installed packages in the system the following command might be useful:

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yum list installed

To reinstall all of them easily one should:

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mkdir emptydirectory
cd emptydirectory
yum reinstall *

Note, that empty directory is required for a successful command execution.
More elegant solution, without empty directory, is:

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yum reinstall \*

Download new version of the PCI ID list:

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update-pciids

update-pciids fetches the current version of the pci.ids file from the primary distribution site and installs it.
This utility requires curl, wget or lynx to be installed. If gzip or bzip2 are available, it automatically downloads the compressed version of the list.
New list will be saved to /usr/share/misc/pci.ids.

Download new version of the USB ID list:

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update-usbids

New list will be saved to /usr/share/misc/usb.ids

Automatic Updates for MaxMind GeoIP free Databases (GeoIP Legacy Databases):

1. Use official MaxMind GeoIP Update program. GeoIP updates require an active GeoIP subscription.
Can find more information at http://dev.maxmind.com/geoip/geoipupdate/

2. Manual download of free (*lite* in terms of MaxMind) databases:
geoipupdate.sh:
#!/bin/sh

GEOIP_MIRROR="https://mailfud.org/geoip-legacy"
GEOIPDIR=/usr/share/GeoIP
TMPDIR=

DATABASES="GeoIP GeoIPv6 GeoIPCity GeoIPCityv6 GeoIPASNum GeoIPASNumv6 GeoIPISP GeoIPOrg"

if [ "${1}" = -f ] || [ "${1}" = --force ]; then
force=true
fi

if [ -d "${GEOIPDIR}" ]; then ...

Sometimes, only one or several files from an .rpm package are required and there is no need to install it on the system.
Let`s find where file(s) will be put after .rpm package install:

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# rpm -qlp nagios-plugins-1.4.15-2.el5.rf.x86_64.rpm | grep rbl
/usr/lib64/nagios/plugins/contrib/check_rbl.c

And extract only it from the archive:

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# rpm2cpio nagios-plugins-1.4.15-2.el5.rf.x86_64.rpm | cpio -ivd ./usr/lib64/nagios/plugins/contrib/check_rbl.c

http://danielmiessler.com/study/tcpdump/

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mkfifo /dev/initctl
reboot -f

The Linux kernel accepts certain 'command-line options' or 'boot time parameters' at the moment it is started. In general this is used to supply the kernel with information about hardware parameters that the kernel would not be able to determine on its own, or to avoid/override the values that the kernel would otherwise detect.

Taken from:

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man bootparam

'panic=N'
By default the kernel will not reboot after a panic, but this option will cause ...

Memcached - high-performance memory object caching system. It requires LibEvent:

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mkdir ~/memcached
cd ~/memcached
wget "http://monkey.org/~provos/libevent-2.0.12-stable.tar.gz"
tar xvfz libevent-2.0.12-stable.tar.gz
cd libevent-2.0.12-stable
./configure && make && make install

Now we are ready to install Memcached:

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cd ~/memcached
wget "http://memcached.googlecode.com/files/memcached-1.4.5.tar.gz"
tar xvfz memcached-1.4.5.tar.gz
cd memcached-1.4.5
./configure --with-lib-event=/usr/local/ && make && make install

Configure dynamic linker run time bindings for LibEvent:

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echo "/usr/local/lib/" > /etc/ld.so.conf.d/libevent.conf
ldconfig


Create init script for Memcached:

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touch /etc/init.d/memcached
chmod +x /etc/init.d/memcached

#!/bin/bash ...

Show mounted file-systems:

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mount | column -t