strace -f -p $(ps -ea f| grep httpsd | cut -f 1 -d " " | xargs | sed -e 's/ / -p /g') 1>/tmp/strace.log 2>&1

When using web services, its sometimes hard to read the serialized json data. I wrote a small helper script to dump the contents

File: /usr/local/bin/json_decode

#!/usr/bin/php
<?php
error_reporting(E_ALL);
ini_set('display_errors',true);
if(!empty($argv[1])) {
        $json = file_get_contents($argv[1]);
}
else {
        $json = '';
        while(!feof(STDIN)) {
                $json .= fgets(STDIN, 1024);
        }
}

$data = json_decode($json);

if($data === null) {
        fwrite(STDERR, "Invalid json data\n");
        exit(1);
}

print_r($data);

Usage:

wget --quiet -O - "http://domain.tld/file.json" | json_decode

find -lname "*" | xargs ls -l

From time to time machines use some swap space due to heavy load. But Linux doesn't free the swap space itself if enough memory is available.

An easy method to flush all disk swap to memory is to disable and re-enable the swap. Eg:

# free -tm
             total       used       free     shared    buffers     cached
Mem:          4096       3269        826          0         31         76
-/+ buffers/cache:       3161        934
Swap:          509        114        395
Total:        4605       3384       1221

# swapoff /dev/xvdb1
# swapon /dev/xvdb1

# free -tm
             total       used       free     shared    buffers     cached
Mem:          4096       3375        720          0         31         78
-/+ buffers/cache:       3265        830
Swap:          509          0        509
Total:        4605       3375       1230

18:23:51 up 666 days,  2:55,  1 user,  load average: 0.01, 0.02, 0.00

If you want to update several hosts at once you can use a for-loop in a shell to execute a command on serveral hosts

for i in 1  3 `seq 4 7` 9; do HOST="1.2.3.$i"; ssh root@$HOST ; done;

As you can see it is very easy to create a custom set of items to loop through. On the one hand you can use any value seperated by a space or you can create a sequence of numbers with the seq-command.

I tried setting up a new blog that should display german date format, but none of the (usually valid) locales worked. The php function setlocale() always returned false. So I searched and found a debian package that fixed my problem, by installing all locales:

apt-get install locales-all