UNIX for Dummies Questions & Answers

Hi

i have written a infinite loop which writes to a file log.txt

while [ 1 ]
do
echo " file in use " >> log.txt
done

i have started this process in one terminal , from another terminal i issued cp command

cp log.txt log2.txt

i was expecting a File in use message but didnt ?

i have checked lines in log2 which is far less than log.txt which is still executing .....

Actually i want to write a backup script which takes backup of our env every day where some or the other files are being used by some process at any given time ....

so can i follow the cp ..? because it was coping even still the file was opened in write mode

or could any one suggest other methods for taking regular backups

any help is much appreciated !!!

as far as i know many daemons using lock file to control their status ( running/stopped/killed )

you may create a lock file on the first line of your backup script so as far the lock file exists dont let your applications/daemons ... to touch your files in any way.

With the script as you've given it, the file is only in use as long as it takes to write one line to it, as on each output redirection the shell opens the file, writes, and closes it immediately afterwards.

so i cannot use the tar or cp for backup , what can be followed for taking regular backup of system where it is in use ...

are you trying to backup a full file system or just a set of files?

Are you wanting to do this by a cron job or will it be manually kicked off everytime you want it backing up?

Are you backing up to tape or just creating .bak files?

there are a few different commands you can use to back files up and they vary on what you should use for what your trying to do?

my requirement is backing one of our directory( we created that directory , not system directory) which is under the root file system.

our application will be running 24x7 ,which access that directory for read/write/executing ... i want to achieve 2 things

1) get the list of files which are in use by application at a given time , i check fuser but could not get clearly

2) getting the full backup of the directory every day using cron , for this i have written a small shell script which has a set of commands to created a tar of a given directory but how to deal with the files which in use by the application at some time

thank you !!

use lsof -p YourApplicationPID to find which files are currently used by the application.

you may use lsof here too , and exclude the files that currently opened in your application when backing up.