Category Archives: Linux

FATAL -> Failed to fork.

February 19, 2017Linux, UbuntuPF

While I was trying to preform an apt-get upgrade i got FATAL -> Failed to fork. error.

According to some fellows around, this issue was probably caused due to the lack of memory!, and it was… 🙂

Free it…. somehow…
Reboot the server?

Composer on CentOS 7

February 12, 2017CentOS, LinuxPF

You need to have PHP installed before. 🙂
Here y’a go…
Under root…..

yum -y update

Switch into the temp directory.

cd /tmp

Install Composer using cURL

curl -sS https://getcomposer.org/installer | php

Make Composer globally accessible

mv composer.phar /usr/local/bin/composer

letsencrypt renew – 404 – Detail: Invalid response

February 11, 2017CentOS, Linux, nginxapache, letsencrypt, nginx, proxy, reverse, sslPF

So!,

letsencrypt renew output

Domain: www.domain.com
Type: unauthorized
Detail: Invalid response from
 http://www.domain.com/.well-known/acme-challenge/WLpdvugG3YzC53RTrZMJcYWsRqcj64vWLw43HNBkMN6:

nginx error log

66.133.XXX.XXX - - [11/Feb/2017:09:33:20 +0100] "GET /.well-known/acme-challenge/WLpdvugG3YzC53RTrZMJcYWsRqcj64vWLw43HNBkMN6 HTTP/1.1" 404 247 "http://www.domain.com/.well-known/acme-challenge/WLpdvugG3YzC53RTrZMJcYWsRqcj64vWLw43HNBkMN6" "Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)"

“Somehow” my domain root has changed.
I had to take a look at /etc/letsencrypt/renewal/domain.com.conf and fix some paths… 🙂

Catch all HTTP GET / POST requests on a Linux server…

January 10, 2017Linuxrequest, sniff, trafficPF

GETs

ngrep -q '^GET .* HTTP/1.[01]'

POSTs

ngrep -q '^POST .* HTTP/1.[01]'

Enter passphrase for key id_rsa.pub

December 17, 2016LinuxPF

So!,

I was trying to SSH a host…
Somehow it was requesting id_rsa.pub……… and asking for an password!

…

This is how I solved it…

ssh -v -i path/to/id_rsa [email protected]

CRITICAL | sd-XXXX.host.net | (Return code of 255 is out of bounds)

November 21, 2016CentOS, Linux, nginx, UbuntuPF

So!,

My nagios was returning a CRITICAL error on one of my servers…

CRITICAL | sd-XXXX.host.net | (Return code of 255 is out of bounds)

and httpd server wasn’t responding….

I think that problem was on IPTABLES / FAIL2BAN ban list. I had 702 banned IPs…
After I clean them up, everything went okay!

captura-de-ecra%cc%83-2016-11-21-as-19-11-52

I was playing hard with them… my bantime was 3600000 (41d) and my findtime was 60000 (16h)…

iptables unban ip and ban entire subnet

October 18, 2016Linuxiptables, unbanPF

iptables

unban ip

List entries with line numbers

iptables -L -v --line-numbers

Delete entry

iptables -D name_of_chain number_of_line_with_IP_that_you_want_to_delete

Let’s imagine that we want to unban 91.194.16.60! chain name is ‘f2b-sshd‘ and line number is 10!

f2b-ssh-unban

iptables -D f2b-sshd 10

Ban entire subnet

Example (banning some chinese sh*t)

iptables -A INPUT -s 119.249.54.0/24 -j DROP
iptables -A INPUT -s 121.18.238.0/24 -j DROP

“SMTP Error: Could not authenticate”

August 19, 2016Linux, Sh*tsemail, gmail, smtpPF

I had to install WP-Mail-Bank in one of my WordPress pages/blogs/store, so it can send emails to *people* 🙂

I was getting “SMTP Error: Could not authenticate” on the test email tab.

I had to went to https://accounts.google.com/b/0/DisplayUnlockCaptcha and continue with this request. This gives us a 10min window to connect to Google in an *unsecure* way. Google detects the connection and allow it for the future.

Reference: http://stackoverflow.com/questions/3949824/smtp-error-could-not-authenticate-in-phpmailer