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


Veracrypt mount

Veracrypr mount opció ha az alábbi hibát kapjuk:


az alábbi opciót kell kiadni:


Linux Huge file edit – hexedit

Elég kis hasznos progi:



tab (switch to ASCII side)
space (delete with white spacce character)
F2 (save)/Ctrl-X (save and exit)/Ctrl-C (exit without saving)



vagy nálam a bináris: hexedit hiányra a megoldás:

/lib(64) -ben a* symlinkelése a és már megy is.