Dariusz on Software

The simplest way to monitor free disk space on Linux serwer, just place it in crontab:

0 8 * * *     df -h | awk '/^\// && $5 > 95 { print "missing space", $0 }'

and ensure e-mail to this user is forwarded to you then you will see e-mail when occupied space is higher than 95% on any disk.

Pretty simple.

Current project I'm working on benefits from automated test suite run on few Linux-based devices. Tests are running 24x7, but sometimes device hangs (reason is still under investigation) and SSH access is blocked then.

In order to track the problem I redirected syslog (busybox-based, BTW) via network and added local automatic monitoring service that will show me when a part of my test installation go down.

The script is really simple and uses GNOME notification tool called notify-send.

#!/bin/sh
if ! ping -q -c 1 google.com > /dev/null
then
    # no network present
    exit
fi
for machine
do
    F=/tmp/$machine
    F2=/tmp/$machine.previous

    if ssh $machine 'echo OK' >$F 2>&1
    then
        rm -f $F $F2
    else
        if test -f $F2
        then
            notify-send "$machine is not present: `cat $F`"
        fi
        mv $F $F2
    fi
done

Details:

• I'm checking if network is available in general (google ping)
• List of SSH machines given on command line
• I assume SSH keys are setup - no password prompt
• Check state is held in /tmp/ directory

Script is started periodically from crontab:

* 9-17 * * 1-5    srv-monitor-ssh alfa beta delta zeus zeus2

and reports failure on second failed check.

Recently I was asked to help with fixing branch that had:

• invalid name (wrong artifact number)
• invalid comment inside (also based on wrong artifact number)

it was a mistake and programmer wanted to preserve changes done on branch, but using different name.

The solution I proposed was to:

1. clone existing branch under different name
2. "amend" last commit on this new branch (to fix comment)
3. push new branch into correct location
4. drop old branch

Sequence of GIT commands was:

$ git branch corect-name origin/invalid-name
(We saved desired SHA with new name)
$ git checkout corect-name
$ git commit --amend
(Fix comment of last commit in editor)
$ git push origin corect-name
(Fixed branch published on our default remote)
$ git push origin :invalid-name
(Weird GIT syntax for deleting remote branches)

For delivering e-mail locally I'm using fetchmail (POP3 based) + local SMTP daemon (for outgoing e-mail). I'd like to see when new e-mail arrives to my desk. It's pretty easy if you connect classic procmail with modern notification tools based on local message buses.

For GNOME command line interface to internal message is notify send. I'm adding call inside my ~/.procmailrc (after filtering out spam e-mail of course):

:0hc
| grep "^From:\|^Subject:" > /tmp/mail.notify-send; DISPLAY=:0.0 notify-send "`cat /tmp/mail.notify-send`"

The result looks like this:

My current project I'm working on is based on embedded systems and QT platform. Of course the very first task in the project is to implement some kind of testing method to get feedback on software quality. The test system is composed from few components:

• Automatic crash reports collected on central server
• Automatic random test runners connected to always-running (24/7) devices to catch crashes

First channel collects all crashes (from human and automated tests), second channel is performed fully automatically. Second channel allows to measure MMTF (mean time between failures) and analyse changes in time, probably helping with estimating current software quality state.

Second testing channel requires automatic test driver to inject random UI events (key presses, remote in my case). I used QT message queue for that purpose:

void TestScript::sendKey(int keyCode) {
 QWSServer::sendKeyEvent(0, keyCode, Qt::NoModifier, 1, false);
 msleep(PRESS_DELAY_MS);
 QWSServer::sendKeyEvent(0, keyCode, Qt::NoModifier, 0, false);
 msleep(WAIT_DELAY_MS);
}

Because QWSServer::sendKeyEvent() must be called in the same process like main application I decided to implement named pipe that will accept key names and render sequence of key events, pseudo-code below:

    while (true) {
        FILE* f = fopen("/tmp/events.pipe", "rt");
        (...)
        while (getline(&buf, &size, f) >= 0) {
            QString line(buf);
            (...)
            if (mapNameToKey.contains(line)) {
                sendKey(mapNameToKey.value(line));
                QCoreApplication::processEvents();
            }
            (...)
        }
        fclose(f);
    }

And usage:

echo "RCU_RIGHT" > /tmp/events.pipe
echo "RCU_OK" > /tmp/events.pipe

That's way I'm able to remotely control application (need just SSH access to the device). And the last (easiest) part is to generate random sequence of events - that can be done by any scripting langugae.

Happy automation!