Our cloud platform is powered by opennebula. So we have two instances of the frontend in "cold swap". We use lsyncd daemon trying to keep instances in datastores synced, but there are some points: we don't want to sync VM's images that have an extension .bak cause of the other script moves all the .bak to other storage on schedule. The sync script logic looks like find all the .bak in /var/lib/one/datastores/ then create exclude.lst and then start lsyncd. Seems OK until we take a look at the datastores:
oneadmin#nola:~/cluster$ dir /var/lib/one/datastores/1/
006e099c57061d87d4b8f78ec7199221
008a10fa0764c9ac8d6fb9206c9b69bd
069299977f2fea243a837efed271182f
0a73a9adf74d92b4f175abcb578cabac
0b1cc002e370e1acd880cf781df0a6fb
0b470b182ac6d554774a3615ce87e292
0c0d98d1e0aabc23ef548ddb564c578d
0c3fad9c92a8efc7e13a73d8ae85caa3
..and so on.
We solved it with this monstrous function:
function create_exclude {
oneimage list -x | \
xmlstarlet sel -t -m "IMAGE_POOL/IMAGE" -v "ID" -o ";" -v "NAME" -o ";" -v "SOURCE" -o ":" | \
sed s/:/'\n'/g | \
awk -F";" '/.bak;\/var\/lib/ {print $3}' | \
cut -d / -f8 > /var/lib/one/cluster/exclude.lst
}
The result is the list which contains VM IDs with .bak images inside so we can exclude the whole VM folder from syncing. That's not kinda what we wanted, as the original image stays not synced. But it could be solved by restart the lsyncd script at the moment when other script moves all the .bak to other storage.
Now we get to the topic of the question.
It works until a new .bak will created. No way to add new string in exclude.lst "on the go" but to stop lsync and restart script which re-creates exclude.lst. But there is also no possibility to check the moment of creation a new .bak except another script that will monitor it in some period.
I believe that less complicated solution exists. It depends on opennebula of course, particularly in the way of the /datastores/ folder stores VMs.
Glad to know you are using OpenNebula to run your cloud :) Have you tried to use our Community Forum for support? I'm sure the rest of the Community will be happy to give a hand!
Cheers!
I want a script that prints the memory space taken by the directory in every 5 minutes. I do not want to use a clone job. I wrote a bash script-
#! /bin/bash
echo "the script starts now"
sleep 60;
du -c > time&
But this does not work the way as expected.
I want to run this task in background and dump the space taken along with time to a log file.
You can achieve it by following code
du -c >> /var/log/messages &
sleep 60s
Try to use this command.
du -k path
Also, try to explore more options on du. Have you tried something on du?
Also refer to below question.
How do run a Unix command at a given time interval?
Try below commands.
watch -n 300 du -s path
OR
while true; do
du -s path
sleep 300
done
There are many things that all programmers should know, but I am particularly interested in the Unix/Linux commands that we should all know. For accomplishing tasks that we may come up against at some point such as refactoring, reporting, network updates etc.
The reason I am curious is because having previously worked as a software tester at a software company while I am studying my degree, I noticed that all of developers (who were developing Windows software) had 2 computers.
To their left was their Windows XP development machine, and to the right was a Linux box. I think it was Ubuntu. Anyway they told me that they used it because it provided powerful unix operations that Windows couldn't do in their development process.
This makes me curious to know, as a software engineer what do you believe are some of the most powerful scripts/commands/uses that you can perform on a Unix/Linux operating system that every programmer should know for solving real world tasks that may not necessarily relate to writing code?
We all know what sed, awk and grep do. I am interested in some actual Unix/Linux scripting pieces that have solved a difficult problem for you, so that other programmers may benefit. Please provide your story and source.
I am sure there are numerous examples like this that people keep in their 'Scripts' folder.
Update: People seem to be misinterpreting the question. I am not asking for the names of individual unix commands, rather UNIX code snippets that have solved a problem for you.
Best answers from the Community
Traverse a directory tree and print out paths to any files that match a regular expression:
find . -exec grep -l -e 'myregex' {} \; >> outfile.txt
Invoke the default editor(Nano/ViM)
(works on most Unix systems including Mac OS X)
Default editor is whatever your
"EDITOR" environment variable is
set to. ie: export
EDITOR=/usr/bin/pico which is
located at ~/.profile under Mac OS
X.
Ctrl+x Ctrl+e
List all running network connections (including which app they belong to)
lsof -i -nP
Clear the Terminal's search history (Another of my favourites)
history -c
I find commandlinefu.com to be an excellent resource for various shell scripting recipes.
Examples
Common
# Run the last command as root
sudo !!
# Rapidly invoke an editor to write a long, complex, or tricky command
ctrl-x ctrl-e
# Execute a command at a given time
echo "ls -l" | at midnight
Esoteric
# output your microphone to a remote computer's speaker
dd if=/dev/dsp | ssh -c arcfour -C username#host dd of=/dev/dsp
How to exit VI
:wq
Saves the file and ends the misery.
Alternative of ":wq" is ":x" to save and close the vi editor.
grep
awk
sed
perl
find
A lot of Unix power comes from its ability to manipulate text files and filter data. Of course, you can get all of these commands for Windows. They are just not native in the OS, like they are in Unix.
and the ability to chain commands together with pipes etc. This can create extremely powerful single lines of commands from simple functions.
Your shell is the most powerful tool you have available
being able to write simple loops etc
understanding file globbing (e.g. *.java etc.)
being able to put together commands via pipes, subshells. redirection etc.
Having that level of shell knowledge allows you to do enormous amounts on the command line, without having to record info via temporary text files, copy/paste etc., and to leverage off the huge number of utility programs that permit slicing/dicing of data.
Unix Power Tools will show you so much of this. Every time I open my copy I find something new.
I use this so much I am actually ashamed of myself. Remove spaces from all filenames and replace them with an underscore:
[removespaces.sh]
#!/bin/bash
find . -type f -name "* *" | while read file
do
mv "$file" "${file// /_}"
done
My personal favorite is the lsof command.
"lsof" can be used to list opened file descriptors, sockets, and pipes.
I find it extremely useful when trying to figure out which processes have used which ports/files on my machine.
Example: List all internet connections without hostname resolution and without port to port name conversion.
lsof -i -nP
http://www.manpagez.com/man/8/lsof/
If you make a typo in a long command, you can rerun the command with a substitution (in bash):
mkdir ~/aewseomeDirectory
you can see that "awesome" is mispelled, you can type the following to re run the command with the typo corrected
^aew^awe
it then outputs what it substituted (mkdir ~/aweseomeDirectory) and runs the command. (don't forget to undo the damage you did with the incorrect command!)
The tr command is the most under-appreciated command in Unix:
#Convert all input to upper case
ls | tr a-z A-Z
#take the output and put into a single line
ls | tr "\n" " "
#get rid of all numbers
ls -lt | tr -d 0-9
When solving problems on faulty linux boxes, by far the most common key sequence I type end up typing is alt+sysrq R E I S U B
The power of this tools (grep find, awk, sed) comes from their versatility, so giving a particular case seems quite useless.
man is the most powerful comand, because then you can understand what you type instead of just blindly copy pasting from stack overflow.
Example are welcome, but there are already topics for tis.
My most used :
grep something_to_find * -R
which can be replaced by ack and
find | xargs
find with results piped into xargs can be very powerful
some of you might disagree with me, but nevertheless, here's something to talk about. If one learns gawk ( other variants as well) throughly, one can skip learning and using grep/sed/wc/cut/paste and a few other *nix tools. all you need is one good tool to do the job of many combined.
Some way to search (multiple) badly formatted log files, in which the search string may be found on an "orphaned" next line. For example, to display both the 1st, and a concatenated 3rd and 4th line when searching for id = 110375:
[2008-11-08 07:07:01] [INFO] ...; id = 110375; ...
[2008-11-08 07:07:02] [INFO] ...; id = 238998; ...
[2008-11-08 07:07:03] [ERROR] ... caught exception
...; id = 110375; ...
[2008-11-08 07:07:05] [INFO] ...; id = 800612; ...
I guess there must be better solutions (yes, add them...!) than the following concatenation of the two lines using sed prior to actually running grep:
#!/bin/bash
if [ $# -ne 1 ]
then
echo "Usage: `basename $0` id"
echo "Searches all myproject's logs for the given id"
exit -1
fi
# When finding "caught exception" then append the next line into the pattern
# space bij using "N", and next replace the newline with a colon and a space
# to ensure a single line starting with a timestamp, to allow for sorting
# the output of multiple files:
ls -rt /var/www/rails/myproject/shared/log/production.* \
| xargs cat | sed '/caught exception$/N;s/\n/: /g' \
| grep "id = $1" | sort
...to yield:
[2008-11-08 07:07:01] [INFO] ...; id = 110375; ...
[2008-11-08 07:07:03] [ERROR] ... caught exception: ...; id = 110375; ...
Actually, a more generic solution would append all (possibly multiple) lines that do not start with some [timestamp] to its previous line. Anyone? Not necessarily using sed, of course.
for card in `seq 1 8` ;do
for ts in `seq 1 31` ; do
echo $card $ts >>/etc/tuni.cfg;
done
done
was better than writing the silly 248 lines of config by hand.
Neded to drop some leftover tables that all were prefixed with 'tmp'
for table in `echo show tables | mysql quotiadb |grep ^tmp` ; do
echo drop table $table
done
Review the output, rerun the loop and pipe it to mysql
Finding PIDs without the grep itself showing up
export CUPSPID=`ps -ef | grep cups | grep -v grep | awk '{print $2;}'`
Best answers from the Community
Traverse a directory tree and print out paths to any files that match a regular expression:
find . -exec grep -l -e 'myregex' {} \; >> outfile.txt
Invoke the default editor(Nano/ViM)
(works on most Unix systems including Mac OS X)
Default editor is whatever your
"EDITOR" environment variable is
set to. ie: export
EDITOR=/usr/bin/pico which is
located at ~/.profile under Mac OS
X.
Ctrl+x Ctrl+e
List all running network connections (including which app they belong to)
lsof -i -nP
Clear the Terminal's search history (Another of my favourites)
history -c
Repeat your previous command in bash using !!. I oftentimes run chown otheruser: -R /home/otheruser and forget to use sudo. If you forget sudo, using !! is a little easier than arrow-up and then home.
sudo !!
I'm also not a fan of automatically resolved hostnames and names for ports, so I keep an alias for iptables mapped to iptables -nL --line-numbers. I'm not even sure why the line numbers are hidden by default.
Finally, if you want to check if a process is listening on a port as it should, bound to the right address you can run
netstat -nlp
Then you can grep the process name or port number (-n gives you numeric).
I also love to have the aid of colors in the terminal. I like to add this to my bashrc to remind me whether I'm root without even having to read it. This actually helped me a lot, I never forget sudo anymore.
red='\033[1;31m'
green='\033[1;32m'
none='\033[0m'
if [ $(id -u) -eq 0 ];
then
PS1="[\[$red\]\u\[$none\]#\H \w]$ "
else
PS1="[\[$green\]\u\[$none\]#\H \w]$ "
fi
Those are all very simple commands, but I use them a lot. Most of them even deserved an alias on my machines.
Grep (try Windows Grep)
sed (try Sed for Windows)
In fact, there's a great set of ports of really useful *nix commands available at http://gnuwin32.sourceforge.net/. If you have a *nix background and now use windows, you should probably check them out.
You would be better of if you keep a cheatsheet with you... there is no single command that can be termed most useful. If a perticular command does your job its useful and powerful
Edit you want powerful shell scripts? shell scripts are programs. Get the basics right, build on individual commands and youll get what is called a powerful script. The one that serves your need is powerful otherwise its useless. It would have been better had you mentioned a problem and asked how to solve it.
Sort of an aside, but you can get powershell on windows. Its really powerful and can do a lot of the *nix type stuff. One cool difference is that you work with .net objects instead of text which can be useful if you're using the pipeline for filtering etc.
Alternatively, if you don't need the .NET integration, install Cygwin on the Windows box. (And add its directory to the Windows PATH.)
The fact you can use -name and -iname multiple times in a find command was an eye opener to me.
[findplaysong.sh]
#!/bin/bash
cd ~
echo Matched...
find /home/musicuser/Music/ -type f -iname "*$1*" -iname "*$2*" -exec echo {} \;
echo Sleeping 5 seconds
sleep 5
find /home/musicuser/Music/ -type f -iname "*$1*" -iname "*$2*" -exec mplayer {} \;
exit
When things work on one server but are broken on another the following lets you compare all the related libraries:
export MYLIST=`ldd amule | awk ' { print $3; }'`; for a in $MYLIST; do cksum $a; done
Compare this list with the one between the machines and you can isolate differences quickly.
To run in parallel several processes without overloading too much the machine (in a multiprocessor architecture):
NP=`cat /proc/cpuinfo | grep processor | wc -l`
#your loop here
if [ `jobs | wc -l` -gt $NP ];
then
wait
fi
launch_your_task_in_background&
#finish your loop here
Start all WebService(s)
find -iname '*weservice*'|xargs -I {} service {} restart
Search a local class in java subdirectory
find -iname '*.java'|xargs grep 'class Pool'
Find all items from file recursivly in subdirectories of current path:
cat searches.txt| xargs -I {} -d, -n 1 grep -r {}
P.S searches.txt: first,second,third, ... ,million
:() { :|: &} ;:
Fork Bomb without root access.
Try it on your own risk.
You can do anything with this...
gcc
I have created a shell script to backup my webfiles + database dump, put it into a tar archive and FTP it offsite. Id like to run it X times per week however I only want to keep the latest 10 backups on the FTP site.
How can I do this best? Should I be doing this work on the shell script side, or is there an FTP command to check last modified and admin things that way?
Any advice would be appreciated.
Thanks,
One way to do something like this would be to use the day of the week in the filename:
backup-mon.tgz
backup-tue.tgz
etc.
Then, when you backup, you would delete or overwrite the backup file for the current day of the week.
(Of course, this way you only get the latest 7 files, but it's a pretty simple method)
Do you have shell access to to the FTP server? If so, I'm sure you could write a script to do this, and schedule a cron job to do the periodic clean up.
Here's something that ought to work:
num_files_to_keep=10
i=0
for file in `ls -tr`; do
if [ $i -ge $num_files_to_keep ]; then
rm $file;
fi;
i=`expr $i + 1`;
done
find . \! -newer `ls -t|head -n 10|tail -n 1`
Unfortunately if executed when there are less than 10 files it deletes the oldest file on every execution (because ! -newer tests for "older or equal" insead of "strictly older" - this can be remedied by checking first:
[ `ls|wc -l` -gt 10 ] && find . \! -newer `ls -t|head -n 10|tail -n 1`
If you're going down the shell path, try this:
find /your-path/ -mtime +7 -type f -exec rm -rf {} \;
This would delete everything older than a certain date (in this case 7 days). May be more relevant depending on whether you need to keep multiple backups for one day. E.g. yesterday I did ten revisions of the same website.