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BananaPi ssh login delay


iwl

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When I ssh to my Banana Pi (I / A20) there is a delay of a few seconds till welcome screen / prompt.

 

With Bananian it was instant as still is with second BananaPi with Bananian and all other kind of Pis I have, rock64 with Bananian no delay also, but faster cpu off course.

 

Tried ssh -vvvv and a look at sshd logs, didn't found something indicating an error yet.

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42 minutes ago, iwl said:

When I ssh to my Banana Pi (I / A20) there is a delay of a few seconds till welcome screen / prompt.

Got such a delay only at the first ssh-login to a system or when the MicroSD-card is very slow (Class 4 to 6) or defective :(

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~$ dd if=/dev/zero of=test.dd bs=4M count=512
512+0 records in
512+0 records out
2147483648 bytes (2.1 GB, 2.0 GiB) copied, 105.904 s, 20.3 MB/s
~$ dd if=test.dd of=/dev/null bs=4M
512+0 records in
512+0 records out
2147483648 bytes (2.1 GB, 2.0 GiB) copied, 95.5337 s, 22.5 MB/s

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Networkanager inserts google dns 8.8.8.8 first to /etc/resolv.conf, local dns after, so bananapi armbian can't resolve own hostname.

 

Can exchange line and resolve works then, but ssh not faster.

 

After reboot 8.8.8.8 first again.

 

How can I change this?

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4 hours ago, iwl said:

After reboot 8.8.8.8 first again.

How can I change this?

the quick & dirty solution is to insert the folowing lines in /etc/rc.local before "exit 0"

echo '# local nameserver' > /etc/resolv.conf
echo 'nameserver 192.168.6.1' >> /etc/resolv.conf
echo '# external nameserver' >> /etc/resolv.conf
echo 'nameserver 8.8.8.8' >> /etc/resolv.conf

I did try to deinstall the networkmanager via apt, but when it it deinstalled mostly the /etc/network/interfaces

via ifupdown doesnt work (also when installed)

 

I dont know why ifupdown / /etc/network/interfaces wont function when the networkmanager is deinstalled :( 

 

[EDIT]

Here is how to disable NetworkManager:
https://edulab.unitn.it/tecnici/how-to-disableremove-network-manager-in-ubuntu-or-debian/

 

Important seems to be that before rebooting/switching to /etc/network/interfaces and /etc/resolv.conf these files should be doublechecked - so that you dont loose your network-connection after restart.

On my OPi PC2 I disabled the NetworkManager service, but after restart the first line of my /etc/resolv.conf is:
# Generated by NetworkManager

but this line wouldnt re-appear

if you do remove the network-manager with

apt remove network-manager

(and then apt autoremove)

 

after that the network-manager couldnt touch you /etc/resolv.con anymore ;)

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3 hours ago, iwl said:

With 20MB/s read/write the card is not defective or very slow and reason for ssh delay being the topic.


Read that topic. It will explain you how wrong you are.

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4 hours ago, iwl said:

With 20MB/s read/write the card is not defective or very slow and reason for ssh delay being the topic.


Surely I can be wrong about this, but until you don't provide useable numbers:

iozone -e -I -a -s 100M -r 4k -r 16k -r 512k -r 1024k -r 16384k -i 0 -i 1 -i 2

SD card remains on the list of suspects. Most of cards can perform solid at sequential R/W while in 4k are disastrous. 

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        Command line used: iozone -e -I -a -s 10M -r 4k -r 16k -r 1024k -i 0 -i 1 -i 2
        Output is in kBytes/sec
        Time Resolution = 0.000001 seconds.
        Processor cache size set to 1024 kBytes.
        Processor cache line size set to 32 bytes.
        File stride size set to 17 * record size.
                                                              random    random     bkwd    record    stride
              kB  reclen    write  rewrite    read    reread    read     write
           10240       4     1883     1706     6310     6206     6243     1533
           10240      16     3122     2925    15066    15129    15035     3036
           10240    1024    11939     6757    22849    22852    22849    18098
 

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On my rock64:

        Command line used: iozone -e -I -a -s 10M -r 4k -r 16k -r 1024k -i 0 -i 1 -i 2
        Output is in kBytes/sec
        Time Resolution = 0.000001 seconds.
        Processor cache size set to 1024 kBytes.
        Processor cache line size set to 32 bytes.
        File stride size set to 17 * record size.
                                                              random    random     bkwd    record    stride
              kB  reclen    write  rewrite    read    reread    read     write     read   rewrite      read   fwrite frewrite    fread  freread
           10240       4     1797     1711     8031     8050     6859     1568
           10240      16     1610     2039    16425    16424    15335     2000
           10240    1024     6633     7163    23310    23297    23273     6384
 

and no significant ssh delay

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It's a very slow SD card, but I guess that should not have a role. I tried on slowest SD card which I found around:

Spoiler

                                                              random    random
              kB  reclen    write  rewrite    read    reread    read     write
           10240       4     1327     1231     7615     7601     5457      794
           10240      16     5537     5830    15768    13551    13847     3672
           10240    1024     7030     7807    20640    20641    17731     5541

 


and delay is around 1s which seems normal for A20. After machine is up and idle.

Ubuntu Bionic / Cubietruck

http://ix.io/1z80 

armbianmonitor -u

was created to not waste time on finding needle in a haystack.

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Quote

ssh slow http://ix.io/1z8x


Logs are anonymized - there is no need to send me this on private. 

 

Nothing suspicious in the logs except this doesn't look good:

[   24.946869] print_req_error: critical medium error, dev sda, sector 0
[   24.946884] Buffer I/O error on dev sda, logical block 0, async page read

How long is this delay? More than 2sec?

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Error is partially broken usb harddisk, tried to shred, removed now and rebooted, don't change the problem.

 

~$ date; ssh -ttt xyz date
Do 24. Jan 20:16:56 STD 2019
Thu Jan 24 20:17:01 CET 2019

 

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