"Cannot read data from SSH server" since 4.4.18 > 5.2

[michael.temmerman]

Hi,


Last week I went from 4.4.18 to 5.0, the day after I did 5.0 to 5.2.

Since than, I almost alwaus get "Cannot read data from SSH server" for some (not all) SSH check on a host called "naslenm03", which uses the password auth method.

The zabbix-server log shows:
33213:20201128:233543.610 item "naslenm03:ssh.run[test,192.168.0.211,22,]" became supported
33216:20201128:233643.567 item "naslenm03:ssh.run[test,192.168.0.211,22,]" became not supported: Cannot read data from SSH server

I'm running Zabbix 5.2.1 on Ubuntu 20.04.1 LTS (GNU/Linux 5.4.0-54-generic x86_64) at home, so no professional or real PROD-environment

Zabbix-server config changes that didn't help so far:
- increased CacheSize to 8M
- set CacheUpdateFrequency=60
- set ValueCacheSize=8M
- set Timeout=10, even went to 30, but didn't help, so returned to 10, I'm thinking about returning to 3

(libssh version running: ii libssh-4:amd64 0.9.3-2ubuntu2.1 amd64 tiny C SSH library (OpenSSL flavor))

What I "finaly" found out:
a) the executed script "df /dev/md3 | tail -n +2 | awk '{ print $4 }'" gives the "Cannot read data from SSH server", but
b) the executed script "df /dev/md3" runs fine
c) the executed script "df /dev/md3 | tail -n +2" gives the "Cannot read data from SSH server"
d) the executed scripts "cat /sys/class/net/eth0/statistics/rx_bytes" and "cat /sys/class/net/eth0/statistics/tx_bytes" run fine every minute

So I get the impression that Zabbix cannot read the data from the SSH server when pipe is used.

Any hints/tips/trics?

Did I miss something in the upgrade notes or other literature? :s

Kind regards,
Michaël

[michael.temmerman]

splitek,


thx for the reply!

I had seen https://www.zabbix.com/forum/zabbix-...2593#post41259, but as Kukulkan post (#7) dated june 2020,
and my libssh version is up-to-date, I thought the source of the issue was me (or Zabbix).

walter.egosson 's post (#8) talks about Debian Buster and libssh v0.8 so I didn't take that post into account

I'll try to compile 0.9.4 and/or 0.9.5 to see whether it's solves my problem and will come back with the results.

[judsondiogofm]

I have this same problem, did you manage to solve it?

[michael.temmerman]

Hi judsondiogofm,


I'm sorry, I haven't managed to solve the problem.

My compile skills aren't good enough to get to version 0.9.4 and/or 0.9.5.

Current libssh version on the Zabbix server (which has the latest Ubuntu 20.04 LTS updates) is still
ii libssh-4:amd64 0.9.3-2ubuntu2.1 amd64 tiny C SSH library (OpenSSL flavor)

The libssh version on the monitored host (an old Western Digital MyBook Live Duo) is much older
ii libssh2-1 0.18-1 SSH2 client-side library

This host is only used as a 2nd back-up, so for me it ain't worth much effort.

Kind regards,
Michaël

[tsueri]

Hi judsondiogofm,


I'm sorry, I haven't managed to solve the problem.

My compile skills aren't good enough to get to version 0.9.4 and/or 0.9.5.

Current libssh version on the Zabbix server (which has the latest Ubuntu 20.04 LTS updates) is still
ii libssh-4:amd64 0.9.3-2ubuntu2.1 amd64 tiny C SSH library (OpenSSL flavor)

The libssh version on the monitored host (an old Western Digital MyBook Live Duo) is much older
ii libssh2-1 0.18-1 SSH2 client-side library

This host is only used as a 2nd back-up, so for me it ain't worth much effort.

Kind regards,
Michaël

I just ran into this. You don't have to compile libssh yourself. Just load their PPA as it is described here: https://www.libssh.org/get-it/

Then simply

apt update

and

apt upgrade -y