Posts Tagged ‘haproxy’

Linux: logrotate fix log file permissions on newly created logs after rotation

Monday, July 5th, 2021

fix logrotate permission issues of newly logrotated files, howto chown chmod logrotate linux logo

If you have to administer a bunch of Web or Application servers you will definetely end up with some machines that has some logrotate misconfiguration.

Perhaps the most common one sysadmin faces is when you have rotated webserver, proxy, mail server logs that gets gzipped with a date timestamp of the rotation and a brand new files is created by logrotate. Such a thing could be seen on various Linux distributions and even a more corporate prodcution ready Linux – es like CentOS and Fedora occasionally end up with issues caused by improperly created user / group permissions (usually root:root) of logrotate. 

The wrong permissions of usually normally logging to file by a service, happens when the log file will get filled (or matches some thresholds) configured by logrotate respective config, the log rotate mechanism will rename this file gzip / bzip it depending on how it is prepared to behave and opens a new one, however the newly produced log file will not have the read write permission which are necessery for the respective service because the service is not running as administrator (root), lets say there is a haproxy daemon running with user / group haproxy, haproxy, like it happeed today on one of our legacy CentOS 6.5 servers.

The sad result is /var/log/haproxy.log or whatever log file stays empty forever even though the service is normally working and you end up blind not seeing what's going on …

To solve the empty file due to logrotate dumping the original file permissions to a wrong one due to misconfiguration or a lack of special configuration it is as easy as setting up the logrotated file to write down the new rotated file to a specic user, this is done with a one line addition of code with a syntax like:

create mode owner group

Below is extract from logrotate man page (man logrotate)

Immediately after rotation (before the postrotate script is run) the log file is created (with the same name as the log file just rotated). mode specifies the mode for the log file in octal (the same as chmod(2)), owner specifies the user name who will own the log file, and group specifies the group the log file will belong to. Any of the log file attributes may be omitted, in which case those attributes for the new file will use the same values as the original log file for the omitted attributes. This option can be disabled using the nocreate option.

 Lets say you have following /etc/logrotate.d/haproxy configuration that is instructing logrotate to do the rotation and this will create empty file with root:root after rotate:

root@haproxy2:/etc/logrotate.d# cat haproxy

/var/log/haproxy.log {
    daily
    rotate 52
    missingok
    notifempty
    compress
    delaycompress
    postrotate
        /usr/lib/rsyslog/rsyslog-rotate
    endscript
}

To make /var/log/haproxy.log be owned by haproxy user and group and chmod to certain owner permissions hence, do add inside the block something like: 

 

/var/log/haproxy.log {
….
        create 664 user group
….
}


i.e. :

/var/log/haproxy.log {
….
        create 644 haproxy hapoxy
….
}

To test the configuration do a logrotate config dry run do:

root@haproxy2:/etc/logrotate.d# logrotate -v -d -f /etc/logrotate.d/haproxy
WARNING: logrotate in debug mode does nothing except printing debug messages!  Consider using verbose mode (-v) instead if this is not what you want.

reading config file /etc/logrotate.d/haproxy
Reading state from file: /var/lib/logrotate/status
Allocating hash table for state file, size 64 entries
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state
Creating new state

 

Handling 1 logs

rotating pattern: /var/log/haproxy.log  forced from command line (52 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/haproxy.log
  Now: 2021-07-05 21:51
  Last rotated at 2021-07-05 00:00
  log needs rotating
rotating log /var/log/haproxy.log, log->rotateCount is 52
dateext suffix '-20210705'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
compressing log with: /bin/gzip

renaming /var/log/haproxy.log.8.gz to /var/log/haproxy.log.9.gz (rotatecount 52, logstart 1, i 8),
renaming /var/log/haproxy.log.7.gz to /var/log/haproxy.log.8.gz (rotatecount 52, logstart 1, i 7),
renaming /var/log/haproxy.log.6.gz to /var/log/haproxy.log.7.gz (rotatecount 52, logstart 1, i 6),
renaming /var/log/haproxy.log.5.gz to /var/log/haproxy.log.6.gz (rotatecount 52, logstart 1, i 5),
renaming /var/log/haproxy.log.4.gz to /var/log/haproxy.log.5.gz (rotatecount 52, logstart 1, i 4),
renaming /var/log/haproxy.log.3.gz to /var/log/haproxy.log.4.gz (rotatecount 52, logstart 1, i 3),
renaming /var/log/haproxy.log.2.gz to /var/log/haproxy.log.3.gz (rotatecount 52, logstart 1, i 2),
renaming /var/log/haproxy.log.1.gz to /var/log/haproxy.log.2.gz (rotatecount 52, logstart 1, i 1),
renaming /var/log/haproxy.log.0.gz to /var/log/haproxy.log.1.gz (rotatecount 52, logstart 1, i 0),
log /var/log/haproxy.log.53.gz doesn't exist — won't try to dispose of it
renaming /var/log/haproxy.log to /var/log/haproxy.log.1
creating new /var/log/haproxy.log mode = 0644 uid = 106 gid = 112
running postrotate script
running script with arg /var/log/haproxy.log: "
        /usr/lib/rsyslog/rsyslog-rotate
"

 

 

root@haproxy2:/etc/logrotate.d# grep -Ei '106|112' /etc/passwd
haproxy:x:106:112::/var/lib/haproxy:/usr/sbin/nologin

You do it for any other service respectively by editting whatever /etc/logrotate.d/file, lets say postfix's /var/log/maillog should be owned with 644 by postfix:postfix.
 

# cat /etc/logrotate/postfix
/var/log/maillog {
….
        create 664 postfix postfix
….
}

Stop haproxy log requests to /var/log/messages / Disable haproxy double logging

Friday, June 25th, 2021

haproxy-logo

On a CentOS Linux release 7.9.2009 (Core) I've running haproxies on two KVM virtual machines that are configured in a High Avaialability cluster with Corosync and Pacemaker, the machines are inherited from another admin (I did not install the servers hardware) and OS but have been received the system for support.
The old sysadmins seems to not care much about the system so they've left the haprxoy with Double logging one time under separate configured log in /var/log/haproxy/haproxyprod.log and each Haproxy TCP mode flown request has been double logged to /var/log/messages as well. As you can guess this shouldn't be so because we're wasting Hard drive space so to fix that I had to stop haproxy doble logging to /var/log/messages.

The logging is done under a separate local pointer local6 the /etc/haproxy/haproxyprod.cfg goes as follows:
 

[root@haproxy01 ~]# cat /etc/haproxy/haproxyprod.cfg

global
    # log <address> [len ] [max level [min level]]
    log 127.0.0.1 local6 debug

 

The logging is handled by rsyslog via the local6, so obviously to keep out the logging from /var/log/messages
The logging to the separate log file configuration in rsyslog is as follows:

local6.*                                                /var/log/haproxy/haproxyprod.log

It turned to be really easy to prevent haproxy get its requests log to /var/log/messages all I had to change is under /etc/rsyslogd.conf

local6.none config has to be placed for /var/log/messages the full line configuration in /etc/rsyslog.conf that stopped double logging is:

# Don't log private authentication messages!
*.info;mail.none;authpriv.none;cron.none;local5.none;local6.none                /var/log/messages