Common errors and troubleshooting commands for Linux.

Posted: October 9, 2013. At: 10:27 AM. This was 4 years ago. Post ID: 6362
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  1. Some useful Linux tips and troubleshooting commands
  2. How to install the restricted codecs in Ubuntu
  3. How to boot an Ubuntu live ISO from the GRUB bootloader
  4. How to re-install the GRUB bootloader using a live Linux CD
  5. How to find out the domain name that goes with an IP address
  6. How to check if a host is up without using ping
  7. List all hard drives and partitions on your computer
  8. Run a command on the Linux shell that will be immune to hangups if you are disconnected

Some useful Linux tips and troubleshooting commands

32bit CPU error.
32bit CPU error.

If you are getting this error when you are attempting to run Ubuntu on your PC; it is due to the fact that your CPU does not support the 64bit operating system that you are trying to run. You would need to use an i386 copy instead. This is due to the obvious limitations of a 32-bit CPU.

How to install the restricted codecs in Ubuntu

To install the required codecs for multimedia playback on Ubuntu; just type this command.

sudo apt-get install ubuntu-restricted-extras

This will install everything that you need to get Ubuntu multimedia playback working.

How to boot an Ubuntu live ISO from the GRUB bootloader

If you wish to copy an Ubuntu live ISO to your hard drive and boot it without using a USB stick or a CDROM, then this posting will help you out.

http://www.securitronlinux.com/bejiitaswrath/how-to-boot-an-ubuntu-iso-without-a-thumb-drive-or-a-cd-read-more-to-find-out/. How to boot an Ubuntu ISO from the GRUB bootloader directly. This really works!

How to re-install the GRUB bootloader using a live Linux CD

http://www.securitronlinux.com/linux-mint-2/re-installing-the-grub2-bootloader-using-a-chroot-with-linux-mint-14/. Using a chroot to re-install the GRUB bootloader.

using aliases on the bash shell to make using the command line faster.

http://www.securitronlinux.com/bejiitaswrath/how-to-use-aliases-with-the-bash-shell-and-some-other-useful-linux-tricks/.

How to find out the domain name that goes with an IP address

Use the nslookup command to find the hostname that is asssociated with an IP address. This is a very useful command.

[email protected]:~$ nslookup 8.8.8.8
Server:		153.107.14.93
Address:	153.107.14.93#53
 
Non-authoritative answer:
8.8.8.8.in-addr.arpa	name = google-public-dns-a.google.com.
 
Authoritative answers can be found from:

How to check if a host is up without using ping

If you are behind a proxy that blocks ping packets and you wish to check if a host is up; then this perl script will fulfil this task just fine.

Here is the output.

root@neo:/home/homer/Documents# ./net.pl
Please type a host to check: -:
8.8.8.8
#-Protocol tcp 
8.8.8.8 is NOT reachable.
#-Protocol udp 
8.8.8.8 is NOT reachable.
#-Protocol icmp 
8.8.8.8 is NOT reachable.
#-Protocol stream 
8.8.8.8 is NOT reachable.
#-Protocol syn 
8.8.8.8 is reachable.

And here is a copy of the script.

#!/usr/bin/perl
 
use warnings;
use strict;
 
use Net::Ping;
 
# code source: http://www.perlmonks.org/?node_id=943892
# More: http://stackoverflow.com/questions/3960595/how-can-i-ping-a-host-with-a-perl-one-liner-with-netping
 
#$| = 1;
print "Please type a host to check: -:\n";
my $host = <>; #Reading input from STDIN.
 
if (length($host) < 3) {
    print "You did not type a host!\n";
    exit(0);
}
 
my @proto = ("tcp", "udp", "icmp", "stream", "syn");
 
foreach my $pro ( @proto ) {
    print "#-Protocol $pro \n";
    my $p = Net::Ping->new($pro);
    chomp($host);
    # Specify source interface of pings
    print "$host is ";
    print "NOT " unless $p->ping($host, 2);
    print "reachable.\n";
    $p->close();
}
 
exit(0);

Use this and at least one of the protocols will work. You need to run this as root to use ICMP probes though.

List all hard drives and partitions on your computer

Use the fdisk -l command as root to list all drives and partitions on your computer. This is useful if you want to install another Linux distribution and you wish to determine which partition you can use.

homer@neo:~/Documents$ sudo fdisk -l
 
Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0008186c
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      206847      102400    7  HPFS/NTFS/exFAT
/dev/sda2          206848   234438655   117115904    7  HPFS/NTFS/exFAT
 
Disk /dev/sdb: 320.1 GB, 320072932352 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142446 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x2774878b
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    29362175    14680064   27  Hidden NTFS WinRE
/dev/sdb2   *    29362176    29566975      102400    7  HPFS/NTFS/exFAT
/dev/sdb3        29566976   418666495   194549760    7  HPFS/NTFS/exFAT
/dev/sdb4       418668542   593827839    87579649    f  W95 Ext'd (LBA)
/dev/sdb5       418668544   490896783    36114120    7  HPFS/NTFS/exFAT
/dev/sdb6       490897408   588553657    48828125    7  HPFS/NTFS/exFAT
/dev/sdb7       588554240   593827839     2636800   82  Linux swap / Solaris
 
Disk /dev/sdc: 8095 MB, 8095006720 bytes
9 heads, 48 sectors/track, 36598 cylinders, total 15810560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1bf0d4df
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048    15808511     7903232    7  HPFS/NTFS/exFAT

You may specify a drive to query this way. I am running Debian 7.1 off an external drive at the moment, so /dev/sda is NTFS.

homer@neo:~/Documents$ sudo fdisk -l /dev/sda
 
Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0008186c
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      206847      102400    7  HPFS/NTFS/exFAT
/dev/sda2          206848   234438655   117115904    7  HPFS/NTFS/exFAT

Run a command on the Linux shell that will be immune to hangups if you are disconnected

The nohup command will allow you to execute a command in an SSH session that will continue to run if you are disconnected. Then you may have peace of mind that your important find command will not be cut off.

For example.

nohup sudo apt-get dist-upgrade &

Then press ENTER twice. This will run the command in the background.

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