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I have come across a situation in the past where someone has unlinked a file by running an 'rm' command against it while it was still being written to by a running process.
The problem manifested itself when a 'df' command showed a filesystem at 100%, but this did not match the total value of a 'du -sk *'.
When this happens, the process continues to write to the file but you can no longer see the file on the filesystem. Stopping and starting the process will, more often than not, get rid of the unlinked file, however this is not always possible on a live server.
When you are in this situation you can use the 'lsof' command above to get the PID of the process that owns the file (in the sample output this is 23521).
Run the following command to see a sym-link to the file (marked as deleted):
$ cd /proc/23521/fd && ls -l
Truncate the sym-link to regain your disk space:
$ > /proc/23521/fd/3
I should point out that this is pretty brutal and *could* potentially destabilise your system depending on what process the file belongs to that you are truncating.
This will perform one of two blocks of code, depending on the condition of the first. Essentially is a bash terniary operator.
To tell if a machine is up:
$ ping -c1 machine { echo succes;} || { echo failed; }
Because of the bash { } block operators, you can have multiple commands
$ ping -c1 machine && { echo success;log-timestamp.sh }|| { echo failed; email-admin.sh; }
Tips:
Remember, the { } operators are treated by bash as a reserved word: as such, they need a space on either side.
If you have a command that can fail at the end of the true block, consider ending said block with 'false' to prevent accidental execution
put it in crontab to get an alert when / is over 89% utilization.
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"
You can, of course, tell MySQL to output results to a file and dictate how to terminate lines, etc. But sometimes you don't have access to the file system MySQL is running on, complicating outputting your results to a CSV, necessitating either annoying hacks or this simple command :D
Save some CPU, and some PIDs. :)
creates a tar.gz with a name like:
backup20090410_173053.tar.gz
of a given directory.
this file was made 10 April 2009 at 5:30:53pm
see date's man page to customize the timestamp format
Replace PACKAGE with desired package name.
Found here: http://mikebeach.org/2011/04/undo-apt-get-build-dep/
