Posts Tagged ‘property’

Log rsyslog script incoming tagged string message to separate external file to prevent /var/log/message from string flood

Wednesday, December 22nd, 2021

rsyslog_logo-log-external-tag-scripped-messages-to-external-file-linux-howto

If you're using some external bash script to log messages via rsyslogd to some of the multiple rsyslog understood data tubes (called in rsyslog language facility levels) and you want Rsyslog to move message string to external log file, then you had the same task as me few days ago.

For example you have a bash shell script that is writting a message to rsyslog daemon to some of the predefined facility levels be it:
 

kern,user,cron, auth etc. or some local

and your logged script data ends under the wrong file location /var/log/messages , /var/log/secure , var/log/cron etc. However  you need to log everything coming from that service to a separate file based on the localX (fac. level) the usual way to do it is via some config like, as you would usually do it with rsyslog variables as:
 

local1.info                                            /var/log/custom-log.log

# Don't log private authentication messages!
*.info;mail.none;authpriv.none;cron.none;local0.none;local1.none        /var/log/messages


Note the local1.none is instructing the rsyslog not to log anything from local1 facility towards /var/log/message. 
But what if this due to some weirdness in configuration of rsyslog on the server or even due to some weird misconfiguration in

/etc/systemd/journald.conf such as:

[Journal]
Storage=persistent
RateLimitInterval=0s
RateLimitBurst=0
SystemMaxUse=128M
SystemMaxFileSize=32M
MaxRetentionSec=1month
MaxFileSec=1week
ForwardToSyslog=yes
SplitFiles=none

Due to that config and especially the FowardToSyslog=yes, the messages sent via the logger tool to local1 still end up inside /var/log/messages, not nice huh ..

The result out of that is anything being sent with a predefined TAGGED string via the whatever.sh script which uses the logger command  (if you never use it check man logger) to enter message into rsyslog with cmd like:
 

# logger -p local1.info -t TAG_STRING

# logger -p local2.warn test
# tail -2 /var/log/messages
Dec 22 18:58:23 pcfreak rsyslogd: — MARK —
Dec 22 19:07:12 pcfreak hipo: test


was nevertheless logged to /var/log/message.
Of course /var/log/message becomes so overfilled with "junk" shell script data not related to real basic Operating system adminsitration, so this prevented any critical or important messages that usually should come under /var/log/message / /var/log/syslog to be lost among the big quantities of other tagged tata reaching the log.

After many attempts to resolve the issue by modifying /etc/rsyslog.conf as well as the messed /etc/systemd/journald.conf (which by the way was generated with this strange values with an OS install time automation ansible stuff). It took me a while until I found the solution on how to tell rsyslog to log the tagged message strings into an external separate file. From my 20 minutes of research online I have seen multitudes of people in different Linux OS versions to experience the same or similar issues due to whatever, thus this triggered me to write this small article on the solution to rsyslog.

The solution turned to be pretty easy but requires some further digging into rsyslog, Redhat's basic configuration on rsyslog documentation is a very nice reading for starters, in my case I've used one of the Propery-based compare-operations variable contains used to select my tagged message string.
 

1. Add msg contains compare-operations to output log file and discard the messages

[root@centos bin]# vi /etc/rsyslog.conf

# config to log everything logged to rsyslog to a separate file
:msg, contains, "tag_string:/"         /var/log/custom-script-log.log
:msg, contains, "tag_string:/"    ~

Substitute quoted tag_string:/ to whatever your tag is and mind that it is better this config is better to be placed somewhere near the beginning of /etc/rsyslog.conf and touch the file /var/log/custom-script-log.log and give it some decent permissions such as 755, i.e.
 

1.1 Discarding a message


The tilda sign –  

as placed to the end of the msg, contains is the actual one to tell the string to be discarded so it did not end in /var/log/messages.

Alternative rsyslog config to do discard the unwanted message once you have it logged is with the
rawmsg variable, like so:

 

# config to log everything logged to rsyslog to a separate file
:msg, contains, "tag_string:/"         /var/log/custom-script-log.log
:rawmsg, isequal, "tag_string:/" stop

Other way to stop logging immediately after log is written to custom file across some older versions of rsyslog is via the &stop

:msg, contains, "tag_string:/"         /var/log/custom-script-log.log
& stop

I don't know about other versions but Unfortunately the &stop does not work on RHEL 7.9 with installed rpm package rsyslog-8.24.0-57.el7_9.1.x86_64.

1.2 More with property based filters basic exclusion of string 

Property based filters can do much more, you can for example, do regular expression based matches of strings coming to rsyslog and forward to somewhere.

To select syslog messages which do not contain any mention of the words fatal and error with any or no text between them (for example, fatal lib error), type:

:msg, !regex, "fatal .* error"

 

2. Create file where tagged data should be logged and set proper permissions
 

[root@centos bin]# touch /var/log/custom-script-log.log
[root@centos bin]# chmod 755 /var/log/custom-script-log.log


3. Test rsyslogd configuration for errors and reload rsyslog

[root@centos ]# rsyslogd -N1
rsyslogd: version 8.24.0-57.el7_9.1, config validation run (level 1), master config /etc/rsyslog.conf
rsyslogd: End of config validation run. Bye.

[root@centos ]# systemctl restart rsyslog
[root@centos ]#  systemctl status rsyslog 
● rsyslog.service – System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2021-12-22 13:40:11 CET; 3h 5min ago
     Docs: man:rsyslogd(8)
           http://www.rsyslog.com/doc/
 Main PID: 108600 (rsyslogd)
   CGroup: /system.slice/rsyslog.service
           └─108600 /usr/sbin/rsyslogd -n

 

4. Property-based compare-operations supported by rsyslog table
 

Compare-operation Description
contains Checks whether the provided string matches any part of the text provided by the property. To perform case-insensitive comparisons, use  contains_i .
isequal Compares the provided string against all of the text provided by the property. These two values must be exactly equal to match.
startswith Checks whether the provided string is found exactly at the beginning of the text provided by the property. To perform case-insensitive comparisons, use  startswith_i .
regex Compares the provided POSIX BRE (Basic Regular Expression) against the text provided by the property.
ereregex Compares the provided POSIX ERE (Extended Regular Expression) regular expression against the text provided by the property.
isempty Checks if the property is empty. The value is discarded. This is especially useful when working with normalized data, where some fields may be populated based on normalization result.

 


5. Rsyslog understanding Facility levels

Here is a list of facility levels that can be used.

Note: The mapping between Facility Number and Keyword is not uniform over different operating systems and different syslog implementations, so among separate Linuxes there might be diference in the naming and numbering.

Facility Number Keyword Facility Description
0 kern kernel messages
1 user user-level messages
2 mail mail system
3 daemon system daemons
4 auth security/authorization messages
5 syslog messages generated internally by syslogd
6 lpr line printer subsystem
7 news network news subsystem
8 uucp UUCP subsystem
9   clock daemon
10 authpriv security/authorization messages
11 ftp FTP daemon
12 NTP subsystem
13 log audit
14 log alert
15 cron clock daemon
16 local0 local use 0 (local0)
17 local1 local use 1 (local1)
18 local2 local use 2 (local2)
19 local3 local use 3 (local3)
20 local4 local use 4 (local4)
21 local5 local use 5 (local5)
22 local6 local use 6 (local6)
23 local7 local use 7 (local7)


6. rsyslog Severity levels (sublevels) accepted by facility level

As defined in RFC 5424, there are eight severity levels as of year 2021:

Code Severity Keyword Description General Description
0 Emergency emerg (panic) System is unusable. A "panic" condition usually affecting multiple apps/servers/sites. At this level it would usually notify all tech staff on call.
1 Alert alert Action must be taken immediately. Should be corrected immediately, therefore notify staff who can fix the problem. An example would be the loss of a primary ISP connection.
2 Critical crit Critical conditions. Should be corrected immediately, but indicates failure in a primary system, an example is a loss of a backup ISP connection.
3 Error err (error) Error conditions. Non-urgent failures, these should be relayed to developers or admins; each item must be resolved within a given time.
4 Warning warning (warn) Warning conditions. Warning messages, not an error, but indication that an error will occur if action is not taken, e.g. file system 85% full – each item must be resolved within a given time.
5 Notice notice Normal but significant condition. Events that are unusual but not error conditions – might be summarized in an email to developers or admins to spot potential problems – no immediate action required.
6 Informational info Informational messages. Normal operational messages – may be harvested for reporting, measuring throughput, etc. – no action required.
7 Debug debug Debug-level messages. Info useful to developers for debugging the application, not useful during operations.


7. Sample well tuned configuration using severity and facility levels and immark, imuxsock, impstats
 

Below is sample config using severity and facility levels
 

# Don't log private authentication messages!
*.info;mail.none;authpriv.none;cron.none;local0.none;local1.none        /var/log/messages


Note the local0.none; local1.none tells rsyslog to not log from that facility level to /var/log/messages.

If you need a complete set of rsyslog configuration fine tuned to have a proper logging with increased queues and included configuration for loggint to remote log aggegator service as well as other measures to prevent the system disk from being filled in case if something goes wild with a logging service leading to a repeatedly messages you might always contact me and I can help 🙂
 Other from that sysadmins might benefit from a sample set of configuration prepared with the Automated rsyslog config builder  or use some fine tuned config  for rsyslog-8.24.0-57.el7_9.1.x86_64 on Redhat 7.9 (Maipo)   rsyslog_config_redhat-2021.tar.gz.

To sum it up rsyslog though looks simple and not an important thing to pre

Cloud Computing a possible threat to users privacy and system administrator employment

Monday, March 28th, 2011

Cloud Computing screenshot

If you’re employed into an IT branch an IT hobbyist or a tech, geek you should have certainly heard about the latest trend in Internet and Networking technologies the so called Cloud Computing

Most of the articles available in newspapers and online have seriously praised and put the hopes for a better future through cloud computing.
But is really the cloud computing as good as promised? I seriously doubt that.
Let’s think about it what is a cloud? It’s a cluster of computers which are connected to work as one.
No person can precisely say where exactly on the cluster cloud a stored information is located (even the administrator!)

The data stored on the cluster is a property of a few single organizations let’s say microsoft, amazon etc., so we as users no longer have a physical possession of our data (in case if we use the cloud).

On the other hand the number of system administrators that are needed for an administration of a huge cluster is dramatically decreased, the every day system administrator, who needs to check a few webservers and a mail server on daily basis, cache web data with a squid proxy cache or just restart a server will be no longer necessary.

Therefore about few million of peoples would have to loose their jobs, the people necessary to administrate a cluster will be probably no more than few thousands as the clouds are so high that no more than few clouds will exist on the net.

The idea behind the cluster is that we the users store retrieve our desktops and boot our operating system from the cluster.
Even loading a simple webpage will have to retrieve it’s data from the cluster.

Therefore it looks like in the future the cloud computing and the internet are about to become one and the same thing. The internet might become a single super cluster where all users would connect with their user ids and do have full access to the information inside.

Technologies like OpenID are trying to make the user identification uniform, I assume a similar uniform user identication will be used in the future in a super cloud where everybody, where entering inside will have access to his/her data and will have the option to access any other data online.

The desire of humans and business for transperancy would probably end up in one day, where people will want to share every single bit of information.
Even though it looks very cool for a sci-fi movie, it’s seriously scary!

Cloud computing expenses as they’re really high would be affordable only for a multi-national corporations like Google and Microsoft

Therefore small and middle IT business (network building, expanding, network and server system integration etc.) would gradually collapse and die.

This are only a few small tiny bit of concerns but in reality the problems that cloud computing might create are a way more severe.
We the people should think seriously and try to oppose cloud computing, while we still can! It might be even a good idea if a special legislation that is aming at limiting cloud computing can be integrated and used only inside the boundary of a prescribed limitations.

Institutions like the European Parliament should be more concerned about the issues which the use of cloud computing will bring, EU legislation should very soon be voted and bounding contracts stop clouds from expanding and taking over the middle size IT business.