Mastering The Command Line :: Page 2

Archive for Mastering The Command Line – Page 2

Case-Insensitive Tabbing in Ubuntu Terminal

by Chris Jean

February 8th, 2009

Using the Linux terminal is a fantastic thing. It gives you access to hundreds of great commands and programs, can make navigating through complex directories quick and easy, and offers tools like tab auto-complete that make doing all this a breeze. However, there is a caveat for some people: Linux is case-sensitive. Personally, I love how Linux is case-sensitive, but I know that not everyone will agree with me.

There are ways to create case-insensitive partitions, but doing this has its own technical and functional limitations. If anyone is interested, drop me a line, and I’ll work on a post on this topic.

For those that don’t like how everything in Terminal is case-sensitive, there is a solution that will relieve some of the pain. You can configure your system to make tab auto-complete case-insensitive even on a case-sensitive file system.

Categories Linux, Tips 'n Tricks
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Forcing a Device to Unmount in Ubuntu Linux

by Chris Jean

February 7th, 2009

I recently ran into an issue where a mounted SSHFS filesystem refused to unmount.

I tried to unmount it from inside Nautilus by right-clicking the mount and selecting Unmount, but this failed with an error message. The error told me that it couldn’t unmount the device and gave a reason of “mount disagrees with the fstab”.

I then edited the fstab (sudo vi /etc/fstab) and commented out the entry for the device. I tried to unmount in Nautilus again, but this time it told me that I couldn’t unmount the device because I wasn’t root and the device was not listed in fstab. I then uncommented the previously commented line and saved the file again.

Time to get dirty. I tried to manually run umount, but it failed:

[chris@home ~]$ sudo umount /mnt/share
umount: /mnt/share: device is busy.
        (In some cases useful info about processes that use
        the device is found by lsof(8) or fuser(1))
[chris@home ~]$

This was getting personal now as the previous messages said nothing about the device being in use. I closed out every application and tried again. Same error message.

I followed the instructions and ran man lsof followed by man fuser to find out more about those recommended commands. fuser was the winner.

fuser allows you to find out detailed information about processes that are using specific files or sockets. In addition to getting information, it allows you to kill processes accessing the file or socket. This was exactly what I was looking for.

After reading up on the fuser syntax, I ran the following:

[chris@home ~]$ sudo fuser -km /mnt/share
/mnt/share/: 9004c
[chris@home ~]$

This command basically translates into “find every process that is accessing the /mnt/share mount point and kill it”. Since I was unsure of the ownership of the processes that would be killed, I ran it with sudo to make sure that any processes could be killed.

The /mnt/share/: 9004c response means that a process with an ID of 9004 was terminated.

Again, I ran:

[chris@home ~]$ sudo umount /mnt/share
[chris@home ~]$

This command cheerily replied with nothing, which is a good sign as it means that the umount command succeeded.

Finally, the mount is unmounted. Now if only I could remember what I was trying to do when this problem happened…

Categories Linux, Tips 'n Tricks
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How to Find Hardware Devices in Ubuntu Linux with lshw

by Chris Jean

January 22nd, 2009

Don’t you hate when you need to know and exact model of a specific hardware component but don’t want to open up the machine or find the original documentation on it? Never fear, Linux has you covered.

There are a variety of ways to find out what kind of hardware you’re running, but one of the easiest ways that gives you large amounts of valuable data is to use lshw (Hardware Lister). I’m running Ubuntu 8.10 (Intrepid Ibex), and lshw is installed by default. You can test if you have lshw installed on you system by running the following command:

[chris@home ~]$ sudo lshw

If you get a large listing spewed out on your terminal, you’re good to go. Skip down to the Using lshw section. If you run the lshw command and get a “bash: lshw: command not found” error, you should be able to install lshw using your system’s package manager easily.

Categories Linux, Tips 'n Tricks
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grep – Why I Love Linux

by Chris Jean

January 21st, 2009

This is part one of what will likely turn into a long running series of posts on Why I Love Linux (WILL). The idea of WILL is to share little bits of what makes me love working with Linux. These could be small simple things such as a little feature here or there, the design concept behind Linux, or some other random thing.

I hope that by sharing what it is that I love about Linux, readers can learn a thing or two along the way.

To kick off this new series, I’m going to talk about one of the first command line tools that you should familiarize yourself with in Linux: grep.

Categories Linux, Tips 'n Tricks
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Flush DNS Cache in Ubuntu

by Chris Jean

January 16th, 2009

As a web developer, I’m always having to work with DNS. Anyone who has dealt with DNS will tell you that caching is simultaneously a great thing and a horrible thing.

Today, I made a mistake with the IP address of a new host, and I needed to flush my DNS cache so that my machine would go and grab the new IP address. I hadn’t done this in Ubuntu before, so I had to figure it out. Fortunately, it’s really easy.

Load Terminal (Applications > Accessories > Terminal)
Type in the following:
sudo service networking restart
Press the Enter key
Put in your password

Done. Enjoy your newly flushed DNS cache.

Categories Linux, Tips 'n Tricks
Comments (4)

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