Archive for linux

Transmission network problem

Recently started in debug mode on Transmission and I see:

[17:42:40.319] UDP Failed to set receive buffer: requested 4194304, got 262142 (tr-udp.c:75)
[17:42:40.319] UDP Please add the line "net.core.rmem_max = 4194304" to /etc/sysctl.conf (tr-udp.c:80)
[17:42:40.319] UDP Failed to set send buffer: requested 1048576, got 262142 (tr-udp.c:86)
[17:42:40.319] UDP Please add the line "net.core.wmem_max = 1048576" to /etc/sysctl.conf (tr-udp.c:91)

By tuning the two variables, higher throughput can be achieved more easily using uTP.

Here’s the relevant part from the changeset :

Since we are using a single UDP socket to implement multiple UTP sockets,
and since we are not always timely in servicing an incoming UDP packet,
it is important to use a large receive buffer. The send buffer is probably
less critical, we increase it nonetheless.

Four megabytes might seem huge for embedded clients, but running behind a dedicated connection, it might even become too small. I recommend using 16 megabytes for receive buffering and 4 for the send buffer. That is, because uTP implements a retransmission algorithm and by scaling up the buffers we can achieve fewer retransmits because of dropped datagrams. Let’s set it up that way.

Check actual settings:

do the modifications:


gigabit e1000e Detected Hardware Unit Hang

If we see it in

the resulution is:


for gentoo, add these lines into



Iptables speciális IPről speciális port-ra forwardolás

Tesztelt / Tested:

Source interface: eno1
Target IP:

Source Port: 922
Target port: 22




Cert lementése remote szerverről linuxon


Keresés tar archivumok fájljain belül

vagy így is megeszi


How to get Apache Tomcat version


Let’s Encrypt howto

Clone Git repo:


Generate apache config and certs:

or with subdomain

lets test it:

Enable auto renewal:

output be similar like this:

add it to crontab:

add a line:

grep list the whole line which matches

If we needs the whole line


apache tomcat multiple instances on gentoo


Follow the information in the help to create new Tomcat instances. Tomcat instances use the following layout:

  • /etc/conf.d/tomcat-SLOT-suffix: configuration file for running Tomcat instance services
  • /etc/init.d/tomcat-SLOT-suffix: controlling script for the Tomcat instance
  • /etc/tomcat-SLOT-suffix/: directory containing standard Tomcat configuration files
  • /var/lib/tomcat-SLOT-suffix/: Catalina base directory
  • /var/log/tomcat-SLOT-suffix/: directory for instance log files

Veracrypt mount

Veracrypr mount opció ha az alábbi hibát kapjuk:


az alábbi opciót kell kiadni: