dw8547's questions

We are using:

root@server:~# /usr/share/logstash/bin/logstash --version
logstash 6.2.4

on:

root@server:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.4 LTS
Release:    16.04
Codename:   xenial

with the following log4j2.properties configuration:

status = error
name = LogstashPropertiesConfig

appender.rolling.type = RollingFile
appender.rolling.name = plain_rolling
appender.rolling.fileName = ${sys:ls.logs}/logstash-${sys:ls.log.format}.log
appender.rolling.filePattern = ${sys:ls.logs}/logstash-${sys:ls.log.format}-%d{yyyy-MM-dd}.log.gz
appender.rolling.policies.type = Policies
appender.rolling.policies.time.type = TimeBasedTriggeringPolicy
appender.rolling.policies.time.interval = 1
appender.rolling.policies.time.modulate = true
appender.rolling.strategy.type = DefaultRolloverStrategy
appender.rolling.strategy.action.type = Delete
appender.rolling.strategy.action.basePath = ${sys:ls.logs}
appender.rolling.strategy.action.condition.type = IfLastModified
appender.rolling.strategy.action.condition.age = 7D
appender.rolling.strategy.action.pathConditions.type = IfFileName
appender.rolling.strategy.action.pathConditions.glob = logstash-${sys:ls.log.format}-*
appender.rolling.layout.type = PatternLayout
appender.rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c] %-.10000m%n

appender.json_rolling.type = RollingFile
appender.json_rolling.name = json_rolling
appender.json_rolling.fileName = ${sys:ls.logs}/logstash-${sys:ls.log.format}.log
appender.json_rolling.filePattern = ${sys:ls.logs}/logstash-${sys:ls.log.format}-%d{yyyy-MM-dd}.log
appender.json_rolling.policies.type = Policies
appender.json_rolling.policies.time.type = TimeBasedTriggeringPolicy
appender.json_rolling.policies.time.interval = 1
appender.json_rolling.policies.time.modulate = true
appender.json_rolling.layout.type = JSONLayout
appender.json_rolling.layout.compact = true
appender.json_rolling.layout.eventEol = true

rootLogger.level = ${sys:ls.log.level}
rootLogger.appenderRef.rolling.ref = ${sys:ls.log.format}_rolling

According to the Apache Log4j 2 documentation for RollingFileAppender:

If the file pattern ends with ".gz", ".zip", ".bz2", ".deflate", ".pack200", or ".xz" the resulting archive will be compressed using the compression scheme that matches the suffix.

We have set our filePattern to:

${sys:ls.logs}/logstash-${sys:ls.log.format}-%d{yyyy-MM-dd}.log.gz

but are finding that the rolled over logs are labelled with the .gz extensions, but are in fact, not compressed, e.g.:

root@server:~# file /var/log/logstash/logstash-plain-2019-01-17.log.gz 
/var/log/logstash/logstash-plain-2019-01-17.log.gz: ASCII text

We have gzip installed. What have we missed? Any help would be appreciated.

I am going through a tutorial on recovering from a database failure and in the tutorial, a failure on the host of the primary database is simulated with:

kill -9 <>

I know that the kill command is used to send a signal to a process, and that 9 represents the SIGKILL signal that terminates a process, but what does the <> argument stand for?

I have read the manual pages for the kill command but still cannot figure out why and what for <> is used.

I'm just going through the logs and noticed that the system run:

test -x /etc/cron.daily/popularity-contest && /etc/cron.daily/popularity-contest --crond

as part of the daily cron jobs. I understand what this does/did except, what does the --crond flag at the end of the command do and why/when is this syntax used?

This question is not a duplicate. Please read it before you mark it as such.

Is it possible to assign nicknames or aliases to users on a Linux sever and SSH into the server using the nicknames? I am thinking something along the lines of the aliases for various commands that get added to the .bashrc or the .bash_aliases file, e.g.:

alias grep='grep --color=auto'

For example, if there is a requirement (business rule) to set up users on the server with their full name, e.g., john_smith instead of just their first name (john) but we want to nickname john_smith fruitloops and we want John to be able to:

ssh john_smith@ip_address

as well as:

ssh fruitloops@ip_address

If it is possible, where would the mapping between a user and their nickname be set up? Would the user fruitloops also need to exists on the sever?

This question is about setting up an alias for a user, not a host.