Source: nixCraft
What command I need to type to display Linux kernel version and other information such as Linux distribution name? How do I check Linux kernel version number?
You need to use the following two commands:
[a] uname - Print kernel and system information.
[b] lsb_release - Print distribution-specific information.
[c] /proc/version file - Print running kernel information.
How to check linux kernel version number?
Open a shell prompt (or a terminal) and type the following command to see your current Linux kernel version:
$ uname -r
Sample outputs:
2.6.32-23-generic-pae
Or type the following command:
$ uname -mrs
Sample outputs:
Linux 2.6.32-23-generic-pae i686
To print all information, enter:
$ uname -a
Sample outputs:
Linux vivek-laptop 2.6.32-23-generic-pae #37-Ubuntu SMP Fri Jun 11 09:26:55 UTC 2010 i686 GNU/Linux
Where,
- 2.6.32-23 – Linux kernel version number
- pae – pae kernel type indicate that I’m accssing more than 4GB ram using 32 bit kernel.
- SMP – Kernel that supports multi core and multiple cpus.
Lire la suite…
Dupliquer un système consiste à installer, sur une machine, exactement les mêmes paquets que sur une autre. La technique n’a rien de nouveau en soi, mais il est toujours bon de la rappeler. Sous les dérivés de Debian, “dpkg” permet d’effectuer cette opération rapidement.
Sur la machine à dupliquer, exporter la liste des paquets installés :
# dpkg --get-selections > lstpkg.dpkg
Sur la machine à installer, commencez par poser un système minimal (installation via le CD-Rom “businesscard” sans sélectionner aucun groupe de paquets). Copiez la liste des paquets exportée depuis la machine à dupliquer et importez la dans le gestionnaire de paquets local :
# dpkg --set-selections < lstpkg.dpkg
puis lancez l’installation des paquets ainsi sélectionnés :
# apt-get dselect-upgrade
Note 1 : si vous souhaitez des machines réellement identique, commencez par copier “/etc/passwd” et “/etc/group” de la machine à dupliquer sur la machine cible afin que les programmes installés utilisent les mêmes UIDs et GIDs (exemple : bind, apache, etc…).
Note 2 : Lors de la sauvegarde des configurations de serveurs, conserver un export de la liste des paquets installés sur chacun d’eux peut faire gagner beaucoup de temps en cas de problème…
Source: admin-linux.fr
According to the official project site:
netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack.
This Linux based firewall is controlled by the program called iptables to handles filtering for IPv4, and ip6tables handles filtering for IPv6. I strongly recommend that you first read our quick tutorial that explains how to configure a host-based firewall called Netfilter (iptables) under CentOS / RHEL / Fedora / Redhat Enterprise Linux. This post lists most simple iptables solutions required by a new Linux user to secure his or her Linux operating system from intruders. Lire la suite…
I want to find out how many times a word (say foo or an IP address) occurs in a text file using the grep command on Linux or Unix-like system?
You can use the grep command to search strings, words, text, and numbers for a given patterns. You can pass the -coption to grep command. It only shows the number of times that the pattern has been matched for each file.
Show the total number of times that the word foo appears in a file named bar.txt
The syntax is:
grep -c string filename
grep -c foo bar.txt
Sample outputs:
3
To count total number of occurrences of word in a file named /etc/passwd root using grep, run:
grep -c root /etc/passwd
To verify that run:
grep --color root /etc/passwd
Pass the -w option to grep to select only an entire word or phrase that matches the specified pattern:
grep -w root /etc/passwd
OR
grep -c -w root /etc/passwd
In this example only match a word being with root:
grep --color -w '^root' /etc/passwd
grep -c -w '^root' /etc/passwd
To show only the matching part of the lines.
grep -o 'root' /etc/passwd
grep -c -o 'root' /etc/passwd
Sample session:
Fig.01: Counting occurrence of words/strings using grep command
there’s always apt-cache policy <package-name> (no sudo needed).
Not installed:
olivier@neews:/$ apt-cache policy gnuift
gnuift:
Installed: (none)
Candidate: 0.1.14-11
Version table:
0.1.14-11 0
500 http://archive.ubuntu.com/ubuntu/ oneiric/universe amd64 Packages
Installed:
olivier@neews:/$ apt-cache policy firefox
firefox:
Installed: 8.0+build1-0ubuntu0.11.10.3
Candidate: 8.0+build1-0ubuntu0.11.10.3
Version table:
*** 8.0+build1-0ubuntu0.11.10.3 0
500 http://archive.ubuntu.com/ubuntu/ oneiric-updates/main amd64 Packages
500 http://archive.ubuntu.com/ubuntu/ oneiric-security/main amd64 Packages
100 /var/lib/dpkg/status
7.0.1+build1+nobinonly-0ubuntu2 0
500 http://archive.ubuntu.com/ubuntu/ oneiric/main amd64 Packages
Or dpkg: dpkg -l | grep -E '^ii' | grep <package name>. When it’s not installed it won’t show output. When it is, it’ll show something like:
olivier@neews:~$ dpkg -l | grep -E '^ii' | grep firefox
ii firefox 8.0+build1-0ubuntu0.11.10.3 Safe and easy web browser from Mozilla
ii firefox-branding 8.0+build1-0ubuntu0.11.10.3 Safe and easy web browser from Mozilla - transitional package
ii firefox-globalmenu 8.0+build1-0ubuntu0.11.10.3 Unity appmenu integration for Firefox
ii firefox-gnome-support 8.0+build1-0ubuntu0.11.10.3 Safe and easy web browser from Mozilla - GNOME support
ii firefox-locale-en 8.0+build1-0ubuntu0.11.10.3 English language pack for Firefox
It's obviously a fuzzier search but handy if you're not sure which package you're looking for.
For manually installed things...
A bit harder but if they're on the current path, you could just run them. That's a bit of mission so I'd rather just run:
oli@bert:/$ which chromium-browser
/usr/bin/chromium-browser
And:
oli@bert:/$ which gnuift
# returns nothing
Which is better?
That depends on the sanity of user. There’s nothing to stop somebody installing something called chromium-browser that isn’t Chromium. They could even package it up incorrectly and install that. Neither method can be 100% certain.
But assuming the owner is sane – packages should be good enough for most people.
