Freezing VIM

This is happen when I press Ctrl + S in your VIM. Cause VIM do not response any input. Means, VIM do not print (but still save) anything you typed. Even when you try to kill them (sending kill signal to VIM).

You can get back your VIM into “normal” condition by pressing Ctrl + Q. And viola.. VIM now print everything you typed before.

The reason is, as Michael Mrozek explained, pressing Ctrl + S will trigger xoff that will disable screen painting. This screen painting will be reenabled by  pressing Ctrl + Q (trigger xon).

Thank’s to Stackoverflow and all.

Redirect error to standard output

Assume we are executing a program and want to read the error. Usually the error output is just running up fastly and then left you at the last error only. So, we need to display it per page. But How. Because Linux send the error output in different ‘channel’ then normal output (called standard output).


The error come out from this program execution will run to the end rather than displayed correctly per page.

$ ./ | more

What you do above is actually display the standard output. So you cannot catch the error, even they still printed in screen.

Redirect to file

Yes, instead of display directly in screen, you can save (read: redirect) the error output to screen. This is what normally I do. Because I can read it later.

$ ./ 2> error.$(date +%Y%m%d-%H%M).log
$ more error.20160101-0920.log  # the filename is example only

But, for some reason, we need to display it directly. What we can do is something like this

$ ./ 2>&1 | more

The command above is to send the error output to standard output (2>&1) and then pipe it to more (you can use less for more interactive navigation). Using more (or less) is my recommended way, due to the output can be very-very long.


Ubuntu 14.04 Tidak Bisa Konek VPN via PPTP


OS : Ubuntu 14.04.2
Versi kernel : 3.13.0-62-generic
Versi gnome network manager :
Versi gnome network manager pptp :
Versi ufw : 0.34~rc-0ubuntu2

Koneksi VPN menggunakan pptp selalu gagal dilakukan. Intip mengintip, dari sini[0] didapatkan solusi berikut (bisa pilih salah satu) :

Menambahkan aturan firewall di ufw

Cara pertama yang bisa dicoba adalah menambahkan aturan firewall di berkas konfigurasi /etc/ufw/before.rules sebelum tulisan # drop INVALID packets

-A ufw-before-input -p 47 -j ACCEPT

# drop INVALID packets (logs these in loglevel medium and higher)

Memuat modul kernel nf_conntrack_pptp

Ini cara kedua. Cara ini dapat dilakukan manual dengan mengetikkan perintah berikut :

$ sudo modprobe nf_conntrack_pptp

Agar otomatis dimuat setiap komputer menyala, tambahkan di berkas /etc/modules baris nf_conntrack_pptp

$ sudo nf_conntrack_pptp >> /etc/modules 

Penjelasan untuk masalah ini terlalu teknis (bagi saya), terkait penanganan paket GRE, seperti bisa dibaca di sini[1].

Fix “PHP Fatal error: Call to undefined function posix_getpwuid()”

Example Error Message

PHP Fatal error:  Call to undefined function posix_getpwuid() in /path/to/your/file.php on line 5


PHP posix extension is not available. Check this by invoking this command in your shell :

$ php -m | grep -i posix

If this output posix then you have posix extension installed.

How to fix


Should be enabled by default when you install php from apt-get.


Need php-process extension installation (the package name is depend on your system, usually started with php-process).

$ sudo yum install php-process.x86_64

Manual Compilation

Based on PHP documentation. This compile option is enabled by default.