Carmen's questions

I have this setup where several applications are going through the load balancer (HAproxy) and accessing the MySQL database.

Several applications -> HAproxy -> MySQL database

I would like to know which specific application is accessing the database. When I did a show processlist on the database, it shows the IP of the HAproxy (of course). Then I tried to do lsof on haproxy and mysql database but it didn't help me (or I just don't know to interpret the results properly). And finally I checked the haproxy logs but it didn't show anything.

Thanks.

I have this logrotate config and I am running on Ubuntu 10.04.

/var/log/mysql/mysql-slow.log {
    daily
    rotate 3
    compress
    notifempty
    missingok
    create 660 mysql adm
    postrotate 
    if test -x /usr/bin/mysqladmin && \
       /usr/bin/mysqladmin  ping &>/dev/null
    then
       /usr/bin/mysqladmin  flush-logs
    fi
endscript

}

I put this in /etc/logrotate.d yesterday and today the log was not rotated.

Below are the things that I have done:

1. I verified that the log is indeed in /var/log/mysql/mysql-slow.log
2. mysqladmin lines work fine when run as root
3. mysql is able to write to the mysql-slow.log

When I did this:

$ logrotate -d -f mysql-slow

reading config file mysql-slow
reading config info for /var/log/mysql/mysql-slow.log 

Handling 1 logs

rotating pattern: /var/log/mysql/mysql-slow.log  forced from command line (3 rotations)
empty log files are not rotated, old logs are removed
considering log /var/log/mysql/mysql-slow.log

log needs rotating
rotating log /var/log/mysql/mysql-slow.log, log->rotateCount is 3
dateext suffix '-20120329'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
renaming /var/log/mysql/mysql-slow.log.3.gz to /var/log/mysql/mysql-slow.log.4.gz     (rotatecount 3, logstart 1, i 3), 
renaming /var/log/mysql/mysql-slow.log.2.gz to /var/log/mysql/mysql-slow.log.3.gz (rotatecount 3, logstart 1, i 2), 
renaming /var/log/mysql/mysql-slow.log.1.gz to /var/log/mysql/mysql-slow.log.2.gz (rotatecount 3, logstart 1, i 1), 
renaming /var/log/mysql/mysql-slow.log.0.gz to /var/log/mysql/mysql-slow.log.1.gz (rotatecount 3, logstart 1, i 0), 
renaming /var/log/mysql/mysql-slow.log to /var/log/mysql/mysql-slow.log.1
creating new /var/log/mysql/mysql-slow.log mode = 0660 uid = 20004 gid = 4
running postrotate script
running script (multiple) with arg /var/log/mysql/mysql-slow.log : " 
    if test -x /usr/bin/mysqladmin && \
       /usr/bin/mysqladmin &>/dev/null
    then
       /usr/bin/mysqladmin flush-logs
    fi
"
compressing log with: /bin/gzip
removing old log /var/log/mysql/mysql-slow.log.4.gz

1. Where is the log that shows that logrotate was successful? I want to see if there is anything that would say that there was a problem.
2. Any ideas on why the logrotate is not working?

I have two central rsyslog server accepting UDP logs from multiple client machines.

Both are configured exactly the same.

For some reason, the 1st server doesn't get the logs from the client machines on time. I mean it will get it but delayed for about an hour or so.

The 2nd server gets the logs from the client machines on time.

As far as I can tell, there are no other process running on both servers and the loads are almost the same.

I know UDP is unreliable but I cannot figure why the 1st server is getting the logs but delayed but the 2nd server is getting it on time.

I have a central server where I stored all the private ssh keys to the different machines that I want to ssh to. Currently, only sysadmins have access to this 'central' server.

Given the above scenario, I like to ask the following questions:

1. How do you protect your private ssh keys? I read about ssh-agent but I am not sure how to use it or if it can be used in this situation.
2. If a sysadmin leaves and he copies all the private ssh keys, then he has access to all the servers. How do you deal with this situation?

I'm running a RedHat 5.5 and I was wondering how I can identify a port to a process.

This is the output of netstat and I'm trying to find the process associated with port 35670:

$ netstat -tulnp
tcp        0      0 0.0.0.0:35670               0.0.0.0:*                   LISTEN      -

I tried the following to get the associated process to this port, but to no avail:

$ lsof -nl | grep TCP
$ fuser 35670/tcp

This finally worked for me.

$ rpcinfo -p
100021    3   tcp  35670  nlockmgr

Without doing the command above, how would you have detected that port 35670 is associated with nlockmgr.

The weird thing is nlockmgr does not show up when I do this:

$ ps aux

On server A, I want to issue the following commands to Server B through ssh.

service network stop
sleep 5
service network start

The problem is because I issued a network 'stop', then my current ssh connection is lost as well. Therefore I cannot execute the succeeding commands (sleep 5 and service network start). Note that I cannot use (service network restart).

Does anyone have a workaround / solution for this?

When I run something like:

$ konsole -e "sleep 30"

I get this message

Konsole is unable to open a PTY (pseudo teletype). It is likely that this is due to an incorrect configuration of the PTY devices. Konsole needs to have read/write access to the PTY devices.

But if I try to run this:

$ gnome-terminal -e "sleep 30"

Then it is fine, and it does not throw any error.

How can I change the read/write access of the Konsole to the PTY devices?

Here is the scenario: On the source server, we added a new disk arrays since the old disk arrays where running out of space. So, I copied the contents from the old disk arrays to the new disk arrays using "cp". Then I unmounted the old disk arrays and mounted the new arrays while preserving the partition names.

On the next day, our rsync process ran and for some reason it did not just copied the incremental / different files but it seems to be going through the whole files and... I am not sure what it is doing, there is huge CPU usage by the process and not a lot of IO usage. So, I guess it is doing some checksum process to compare the data between the source and destination but not copying the files?

Anyway, has anyone seen this rsync behavior before? And what triggered this behavior? Is it because I "cp" the files and therefore the files are different? Is there a file where rsync keeps a list of files that it has scanned before so that it knows it will just copy the incremental files?

I have a very basic and newbie question. I was told that we have a "Gigabit Network". So, I ran a quick scp test by copying a file to another machine and the transfer rate is only 35MB/sec.

Shouldn't the transfer rate be near the 1GB/sec?

Also, is there a command line that will tell me that I have a "Gigabit network"? Eg. will ifconfig tell me that?

Here's my scenario: my host is a Windows XP, and I have a guest OS of Ubuntu 8.04. I'm using VirtualBox for this.

I have successfully configured my DNS server in my Ubuntu OS. And if I do the following commands, all of them will give me the corresponding IP address of my DNS server.

dig example.com nslookup ns1.example.com host ns1.example.com

But when I try to ping my DNS server from the host (Windows XP), it says it cannot find the DNS server. Also, if I try to ping my DNS server from another PC, it does not seem to find the DNS server as well.