It is sometimes useful not only to know your repo list covers you for all the stack of software you want but also where does a package actually reside.
The repoquery command comes to the rescue.
EPEL stands for Extra Packages for Enterprise Linux. This is a massive collection of packages that are very useful for the building of many modern stacks and include many tools for the running and maintenance of systems.
The homepage of EPEL is here: http://fedoraproject.org/wiki/EPEL.
You can browse the package set using repoview:
Installing on Centos 5.x & 6.x:
For EL5:
su -c 'rpm -Uvh http://mirror.switch.ch/ftp/mirror/epel/5/i386/epel-release-5-4.noarch.rpm' ... su -c 'yum install puppet'
For EL6:
su -c 'rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm' ... su -c 'yum install puppet'
For EL7
sudo yum install epel-release
#vim /etc/sysconfig/network
Use something like
HOSTNAME=testarossa.maranello.local
to overwrite the default name and domain of the server.
e.g.
NETWORKING=yes HOSTNAME=testarossa.maranello.local
To avoid rebooting issue the following :
hostname testarossa.maranello.local
That will set it for the current session.
To monitor TCP and UDP connections the following command is very useful:
netstat -t -u
to have a continuous update use the watch command:
watch netstat -t -u
There is a much stronger tool for real time analysis called iptraf.
It is quite self explanatory :
at command line run
iptraf
This tool has many functions and is text mode menu ncurses based application really worth learning.
The yum message “Warning: RPMDB altered outside of yum.” or, as the yum message said for a few months, “Warning: RPMDB has been altered since the last yum transaction.” means some application has altered the rpm database (installed or removed a package) without going through the Yum APIs. This is almost always due to someone using rpm directly (Ie. rpm -ivh blah.rpm), but another possibility is an application built on top of the rpm APIs (Ie. smart, apt, zypp). While it’s possible that someone has hacked your machine and altered the rpmdb maliciously, it would have to be done poorly to trigger this warning.
There are three main sets of reasoning behind bringing this to the users attention.
There are now a few features in yum, requested by users of the package management system, that require yum is aware of all package actions on the system. Here a few of the current ones:
This is not a complete list, and as more package management features are implemented they are much more likely to be implemented at the yum layer than at the rpm layer. Not because rpm is bad, but for the same reasons that the above features were implemented in yum, it’s much easier and faster to implement them there.
# yum clean all
Setting up NTP is very important for a host of application especially clusters and applications like DBs requiring all the servers to be critically time-wise synced.
Install NTP on Red Hat and CentOS 6
$ yum install ntp
$ chkconfig ntpd on
$ ntpdate pool.ntp.org
$ service ntpd start
Install NTP on Ubuntu
The following three commands display the current routing table:
# route
Output:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.1.0 * 255.255.255.0 U 0 0 0 ra0 default dsl-router 0.0.0.0 UG 0 0 0 ra0
# /sbin/route
Output:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 191.255.255.0 * 255.255.255.0 U 0 0 0 eth0 169.254.0.0 * 255.255.0.0 U 0 0 0 eth0 default 191.255.255.1 0.0.0.0 UG 0 0 0 eth0
You can use -n option, to display numerical addresses instead of trying to determine symbolic host names (via dns or /etc/hosts file). This is useful if you are trying to determine why the route to your nameserver has vanished.$
#/sbin/route -n
Output:
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 191.255.255.0 0.0.0.0 255.255.255.0 U 0 0 0 venet0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 venet0 0.0.0.0 191.255.255.1 0.0.0.0 UG 0 0 0 venet0
Please note that a destionation entry 0.0.0.0 (or default) is the default gatway. In above example 191.255.255.1 is a default gatway.
The syntax is as follows:
route add default gw {IP-ADDRESS} {INTERFACE-NAME}
Where,
For example if your router IP address is 192.168.1.254 type the following command as the root user:
# route add default gw 192.168.1.254 eth0
OR use hostname such as dsl-router:
# route add default gw dsl-router eth0
If you find above command hard to use, consider using GUI tools. If your are using Red Hat/CentOS/Fedora core Linux type following command:
# redhat-config-network
OR
If you are using other Linux distribution use command:
# network-admin
Iostat is a very powerful tool for monitoring the throughput of your storage subsystems. Especially to locate bottle necks and pinpoint possible upgrade scenarios. Not immediately visible here is how to install it on Centos 5.x and 6.x.
We shall use the whatprovides tool in yum to locate the packages that provide iostat
To install vim
[root@testarossa-00-0c-29-47-8f-35 ~]# yum whatprovides vim-enhanced
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirror.crazynetwork.it
* epel: fr2.rpmfind.net
* extras: mirror.crazynetwork.it
* updates: mirror.crazynetwork.it
2:vim-enhanced-7.0.109-7.el5.i386 : A version of the VIM editor which includes
: recent enhancements.
Repo : base
Matched from:
[root@testarossa-00-0c-29-47-8f-35 ~]# yum install vim-enhanced-7.0.109-7.el5.i386
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirror.crazynetwork.it
* epel: ftp.uni-koeln.de
* extras: mirror.crazynetwork.it
* updates: mirror.crazynetwork.it
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package vim-enhanced.i386 2:7.0.109-7.el5 set to be updated
--> Processing Dependency: vim-common = 2:7.0.109-7.el5 for package: vim-enhanced
--> Running transaction check
---> Package vim-common.i386 2:7.0.109-7.el5 set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
vim-enhanced i386 2:7.0.109-7.el5 base 1.2 M
Installing for dependencies:
vim-common i386 2:7.0.109-7.el5 base 6.4 M
Transaction Summary
================================================================================
Install 2 Package(s)
Upgrade 0 Package(s)
Total download size: 7.7 M
Is this ok [y/N]: y
Downloading Packages:
(1/2): vim-enhanced-7.0.109-7.el5.i386.rpm | 1.2 MB 00:03
(2/2): vim-common-7.0.109-7.el5.i386.rpm | 6.4 MB 00:18
--------------------------------------------------------------------------------
Total 344 kB/s | 7.7 MB 00:22
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : vim-common 1/2
Installing : vim-enhanced 2/2
Installed:
vim-enhanced.i386 2:7.0.109-7.el5
Dependency Installed:
vim-common.i386 2:7.0.109-7.el5
Complete!
[root@testarossa-00-0c-29-47-8f-35 ~]#
The following command gives a neat list of the Devices and their IPs / details without all the gruesome details.
ifconfig | egrep "Link|inet"
A sample result would be:
[root@testarossa-00-0c-29-47-8f-35 vm]# ifconfig | egrep "Link|inet" eth0 Link encap:Ethernet HWaddr 00:0C:29:47:8F:2B inet addr:192.168.47.135 Bcast:192.168.47.255 Mask:255.255.255.0 eth1 Link encap:Ethernet HWaddr 00:0C:29:47:8F:35 inet addr:192.168.1.71 Bcast:192.168.1.255 Mask:255.255.255.0 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 peth1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif0.1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF vif4.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF virbr0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0 xenbr1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF [root@testarossa-00-0c-29-47-8f-35 vm]#