Linux: Boot a 2TB+ partition or Larger Array Using Grub

Posted on in Categories CentOS, data center, fedora linux, File system, Gentoo Linux, Hardware, High performance computing, Howto, kernel, Linux, Linux Scalability, Linux Virtualization, RedHat/Fedora Linux, Storage, Tips, vmware, xen last updated December 4, 2008

I’ve already written about creating a partition size larger than 2TB under Linux using GNU parted command with GPT. In this tutorial, I will provide instructions for booting to a flat 2TB or larger RAID array under Linux using the GRUB boot loader.

Linux: Should You Use Twice the Amount of Ram as Swap Space?

Posted on in Categories data center, Debian Linux, fedora linux, File system, FreeBSD, Gentoo Linux, kernel, Linux, Linux desktop, Linux laptop, OpenBSD, RedHat/Fedora Linux, Solaris, Storage, Suse Linux, Tuning, Ubuntu Linux, UNIX last updated June 8, 2017

Linux and other Unix-like operating systems use the term “swap” to describe both the act of moving memory pages between RAM and disk and the region of a disk the pages are stored on. It is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast as swap partitions. Now, many admins (both Windows and Linux/UNIX) follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. Let us say I’ve 32GB RAM, should I set swap space to 64 GB? Is 64 GB of swap space required? How big should your Linux / UNIX swap space be?

Linux / UNIX: Find Out If a Directory Exists or Not

Posted on in Categories CentOS, Debian Linux, File system, Gentoo Linux, Howto, Linux, Open source coding, programming, RedHat/Fedora Linux, Shell scripting, Suse Linux, Sys admin, Ubuntu Linux, UNIX last updated November 16, 2008

I’ve already written a small tutorial about finding out if a file exists or not under Linux / UNIX bash shell. However, couple of our regular readers like to know more about a directory checking using if and test shell command.

Download Of The Day: GIMP 2.6 For Linux / Windows / Mac OS X

Posted on in Categories Debian Linux, Download of the day, Gentoo Linux, Gnome, GNU/Open source, Linux, Linux desktop, OS X, Ubuntu Linux, UNIX, windows vista last updated October 1, 2008

GIMP version 2.6 has been released and available for download. It is a free raster graphics editor used to manipulate digital graphics and photographs under Linux and other operating systems. It is often used as a free software replacement for Adobe Photoshop, the most widely used bitmap editor.

Linux / UNIX: Geany Lightweight Integrated Development Environment

Posted on in Categories C Programming, CentOS, Debian Linux, Gentoo Linux, Gnome, Linux desktop, Open source coding, RedHat/Fedora Linux last updated July 9, 2008

Geany is cross platform (UNIX/Windows/BSD) fast, powerful, easy to use integrated development environment for PHP, Java, C and much more. If you wanted to quickly edit source code, Geany is for you. Here’s an introduction to using Geany’s built-in features, including the IDE and built-in development capabilities.

Download TrueCrypt Open Source Full Disk Encryption Software

Posted on in Categories CentOS, Data recovery, Download of the day, Gentoo Linux, GNU/Open source, Hardware, Howto, Linux, Linux desktop, Linux laptop, OS X, RedHat/Fedora Linux, Save money with FOSS, Windows, windows vista last updated July 8, 2008

TrueCrypt version 6.0 has been released and available for download. It is free open-source hard disk encryption software for Windows Vista/XP, Mac OS X, and Linux system.

Linux Configure Netconsole To Log Messages Over UDP Network

Posted on in Categories CentOS, Debian Linux, File system, FreeBSD, Gentoo Linux, GNU/Open source, Hardware, kernel, Linux, Linux distribution, Linux Log Management, Security, Sys admin, Tips, Troubleshooting, Ubuntu Linux last updated July 2, 2008

Linux netconsole kernel module allows dmesg output to be transmitted via the syslogd network. It is kernel-level network logging over udp allowing debugging of problem where disk logging fails and serial consoles are impractical. This is a step-by-step mini howto about netconsole configuration under Red Hat, CentOS, Fedora and Debian Linux.

Get Information about All Running Services Remotely

Posted on in Categories Debian Linux, FreeBSD, Gentoo Linux, Hardware, Howto, Linux last updated January 29, 2008

From my mailbag the other day I received an interesting suggestion about obtaining information regarding all running process and network connections remotely using inetd / xinetd :

SSH client can be used to execute a command(s) on a remote UNIX box. Same technique can be used to get current network and system information using netstat information:
ssh [email protected] netstat -a
ssh [email protected] netstat -tulpn

He suggests that above command can be run via inetd / xinetd so that admin can connect easily and get information using telnet from 100s UNIX boxes. All you have to do is open /etc/inetd.conf under UNIX / Linux:
# vi /etc/inetd.conf
Append following line:
netstat stream tcp nowait root /bin/netstat netstat -a
Restart inetd:
# /etc/init.d/openbsd-inetd restart
Next, use telnet to connect to the netstat service (port 15) and get network connection information:
$ telnet server-name netstat
$ telnet 192.168.1.5 15

Output:

Trying 192.168.1.5...
Connected to 192.168.1.5.
Escape character is '^]'.
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 *:6881                  *:*                     LISTEN
tcp        0      0 *:6081                  *:*                     LISTEN
tcp        0      0 *:nfs                   *:*                     LISTEN
tcp        0      0 localhost:6082          *:*                     LISTEN
tcp        0      0 *:54053                 *:*                     LISTEN
tcp        0      0 *:59275                 *:*                     LISTEN
tcp        0      0 *:netstat               *:*                     LISTEN
tcp        0      0 *:sunrpc                *:*                     LISTEN
tcp        0      0 localhost:webcache      *:*                     LISTEN
tcp        0      0 *:43218                 *:*                     LISTEN
tcp        0      0 *:domain                *:*                     LISTEN
tcp        0      0 localhost:ipp           *:*                     LISTEN
tcp        0      0 *:telnet                *:*                     LISTEN
tcp        0      0 *:3128                  *:*                     LISTEN
tcp        0      0 localhost:smtp          *:*                     LISTEN
tcp        0      1 vivek-desktop.loc:48925 bas4-kitchener06-:56662 SYN_SENT
tcp        0      0 vivek-desktop.loc:54791 customer5673.pool:16273 ESTABLISHED
tcp        0      0 vivek-desktop.loc:38398 59.94.1xx.yy:45483      ESTABLISHED
tcp        0      0 vivek-desktop.loc:42048 60.21.zz.yyy:23235       ESTABLISHED
...........
....
....
unix  3      [ ]         STREAM     CONNECTED     15973
unix  3      [ ]         STREAM     CONNECTED     15947    /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     15946
unix  3      [ ]         STREAM     CONNECTED     15936    /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     15935
unix  2      [ ]         DGRAM                    15931
unix  3      [ ]         STREAM     CONNECTED     15916
unix  3      [ ]         STREAM     CONNECTED     15915
unix  2      [ ]         DGRAM                    15906
Connection closed by foreign host.

There are few problems with this solution:
a] Unnecessary service running at port # 15

b] Telnet protocol is not secure

c] I strongly recommend using ssh and password-less login for scripts to obtain this kind of information:
ssh [email protected] netstat -a
ssh [email protected] df -H
ssh [email protected] free -m
ssh [email protected] /path/to/script.pl