Re-read The Partition Table Without Rebooting Linux System

Posted on in Categories File system, Linux, RedHat/Fedora Linux, Sys admin, Tips, Troubleshooting, Ubuntu Linux last updated July 17, 2016

If you are using hot swappable hard disk and created new partition using fdisk then you need to reboot Linux based system to get partition recognized. Without reboot you will NOT able to create filesystem on your newly created or modified partitions with the mke2fs command.

However with partprobe command you should able to create a new file system without rebooting the box. It is a program that informs the operating system kernel of partition table changes, by requesting that the operating system re-read the partition table.

Moving /home Data From Old System To a New Linux System

Posted on in Categories Howto, Linux last updated April 2, 2012

Recently a friend of mine, brought a new Laptop. He installed Red Hat Enterrpise Linux workstation 4.0. However, after installation he realized that he lost all his Mozilla thunderbird emails and Firefox bookmarks, chat client logs and other files.

I told him just copy all old files from /home/$you to a new system /home/$you directory. He was trying some age-old tutorial from net, which explains how to copy files using tar and restore it back to new system. During this procedure, he was messing up with file system permission.

How do I find out if my Linux server CPU can run a 64 bit kernel version (apps) or not?

Posted on in Categories CentOS, Debian Linux, Gentoo Linux, Howto, Linux, Linux desktop, RedHat/Fedora Linux, Sys admin, Tips, Troubleshooting last updated September 7, 2007

It happens many times. Often new Linux system administrators and user(s) get confused. They are not able to determine if Linux system can run a 64 bit kernel version (and application) or not. There is simple way to find out:

(a) Ask your hardware vendor

(b) Find out yourself by reading manuals

(c) Or run the following commands:
Here is output from one of my production Dual Opteron server:
$ less /proc/cpuinfo
Output:

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 5
model name      : AMD Opteron (tm) Processor 848
stepping        : 10
cpu MHz         : 2197.161
cache size      : 1024 KB
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall
nx mmxext lm 3dnowext 3dnow
bogomips        : 4308.99
TLB size        : 1088 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp

processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 5
model name      : AMD Opteron (tm) Processor 848
....
...
*** Output truncated ***
....

Look for flag entry in above output. If you see lm flags then you will able to run 64 bit kernel and applications. Now consider output from my Workstation (32 bit system you will not able to find out lm [long mode] flag):

$ less /proc/cpuinfo

Output:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 1
model name      : Intel(R) Celeron(R) CPU 1.70GHz
stepping        : 3
cpu MHz         : 1717.118
cache size      : 128 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
bogomips        : 3437.80

You can also type command uname command to find out this info:

$ uname -a

Output:

Linux ora100 2.6.5-7.252-smp #1 SMP Tue Feb 14 11:11:04 UTC 2006 x86_64 x86_64 x86_64 GNU/Linux

The x86_64 confirms you can run 64 bit apps. You can also use live CD such as Knoppix to boot and find out this info.

Read UNIX / Linux System IP Address In a Shell Script

Posted on in Categories Linux, Shell scripting last updated May 28, 2011

Reading an IP address in shell script required many time. However, different Linux distribution stores IP address in different files. If you are looking to run script under different UNIX like OSes such as Solaris or FreeBSD then you need to use the ifconfig command. The ifconfig command is not just used to configure a network interface, but it can be use to obtained information such as network IP, netmask and much more.

How do I Use Multiple Screens on One Terminal over ssh session?

Posted on in Categories CentOS, Debian Linux, Gentoo Linux, GNU/Open source, Linux, Linux desktop, Networking, RedHat/Fedora Linux, Shell scripting, Sys admin, Tips, Ubuntu Linux, UNIX last updated January 24, 2009

Most of the time GUI is not available on remote Linux system, you login over ssh and start to work, if you need to run two or three task at a time, you login over ssh two or three times. However, with screen windows manager utility you can run multiple terminals at the same time from single console login over ssh session (UNIX guru uses the term called multiplexing for this concept). Any seasoned Linux admin should be aware of this nifty tool :)