Witek's questions

I have purchased a cheap virtual server (running with Ubuntu, with 4 virtual? CPUs and guaranteed 8GB RAM, SSD). I started Tomcat8 with my web application (with -Xmx4096m). The startup time is very, very slow. It is about 50 times slower, then on my notebook. I would like to know what the bottleneck is. Is it CPU? Is ist the disk?

top or htop show me about 1% CPU usage and 300MB mem usage. Since it is a virtual server I have no idea if these are reliable. How can I check if I use up all the CPU given to me?

--- update ---

After stopping all services and starting tomcat alone, things got faster. the problem was mysql/php/tt-rss. But I still have no idea how this happened. Since CPU was at 1% I think it was the SSD. But where and how could I have seen this?

I have created my own upstart script in /etc/init, which I can start and stop.

Now I want that service to be restarted when a file (/etc/my-app/restart-requested.txt) exists (or better is touched).

My solution with previous /etc/init.d/ service was a cron-job which regularily checked for the restart-file and called restart when the file existed.

Is there a better solution with upstart?

I got a MySQL DDL file ddl.sql which I would like to import. It starts like this:

--=20MySQL=20dump=2010.11=0A--=0A--=20Host:=20localhost=20=20=20=20=
Database:=20ww=0A--=20=
------------------------------------------------------=0A--=20Server=20=

I think it is a kind of quoted printable encoding. When I try to import this via mysql testdb < ddl.sql I get the following error:

ERROR 1064 (42000) at line 1: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '--=20MySQL=20dump=2010.11=0A--=0A--=20Host:=20localhost=20=20=20=20=Database:=2' at line 1

Is there a way MySQL can read this kind of files? Or do I have to convert it first? Any ideas how?

I am using the following command to delete old backup files:

find backups/ -name "bak_*.tbz" -mmin +4800 -exec rm -vf {} \;

The problem: When there are no new files, than all files are deleted. I would likke to keep the newest one in such case.

What is an elegant way to delete old files except the newest one?

From time to time connection to my server is very slow. This could be that someone is doing large uploads or downloads. Since I have a lot of software on my server I would like to find out, which process is responsible for the traffic.

Is there a simple command which lists processes which are currently doing network communication, sorted by the amout of traffic that was created in the last x seconds?

My system is running Ubuntu.

My Ubuntu 11.04 server on the internet has some strange behavior since a few days. It runs perfectly fine with some Java web applications. Then, suddenly it does not accept connections anymore. When I try to ssh or to http-connect my server I get no response, until I get timeout. But ping works perfectly. nmap also works:

Starting Nmap 5.21 ( http://nmap.org ) at 2011-08-29 10:52 CEST
Nmap scan report for ...
Host is up (0.020s latency).
Not shown: 994 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh
25/tcp   open  smtp
53/tcp   open  domain
443/tcp  open  https
3000/tcp open  ppp
3128/tcp open  squid-http

After reboot, everything works again for some hours.

What could this be? Or how to analyse this problem?

My Squid HTTP proxy works fine with authentication. Here is the config:

auth_param basic program /usr/lib/squid/pam_auth
auth_param basic children 5
auth_param basic realm test-proxy
auth_param basic credentialsttl 4 hours
auth_param basic casesensitive off

But I want that my locally running applications which use the proxy don't have to authenticate. How to disable authentication for requests from localhost?

My server causes too much traffic, so I have installed ntop to monitor it.

On the Summary -> Traffic page in the Global TCP/UDP Protocol Distribution table I can see the traffic is periodically caused by HTTP.

On the All Protocols -> Traffic page in the first row there is the traffic (94,4%). But the first column (Host) shows my own server. Why is this?

When clicking there, I can see that the traffic in the Host Traffic Stats table. It is all in the Tot. Traffic Rcvd column. Therefore I think, one of my applications ist periodically downloading something big, or a lot.

But how to find out, what was downloaded? What are the downloaded URLs or at least the hosts that caused the most traffic?

My file server (Ubuntu) on the internet runs OpenSSH, where users upload and download files using scp or WinSCP. At the same time, the server runs some web applications (http), which need higher priority.

Is there a way to give HTTP priority over SSH file transfer? If not, can I limit SSH bandwidth?

I have a Java web application (myapp.war) which I want do deploy to Tomcat, which is provided by Ubuntu (package tomcat6). This works by placing myapp.jar to the webapps direcotry. This works.

Now, my application has to store some data to local files. My idea was to write to the users home direcotry or to the current work direcotry. But on Ubuntu 10.04 the user is tomcat6, its home is /usr/lib/tomcat6/ and the current work directory is /var/lib/tomcat6/. And both belong to root. Therefore writing is impossible.

So where should a web application store its files?

On Ubuntu it is possible to have multiple JVMs at the same time. The default one is selected with update-alternatives. But this does not set the JAVA_HOME environment variable, due to a debian policy.

I am writing a launcher script (bash), which starts a java application. This java application needs the JAVA_HOME environment variable. So how to get the path of the JVM which is currently selected by update-alternatives?

On my ubuntu server I have an application MyApp which runs as a daemon with its own user myapp.

Then I have a web application MyPortal which runs in apace httpd as user www-data. This application serves a web page with a Redeploy MyApp button. When clicking this button I want to start the script redeploymyapp. This script stops the MyApp deamon, upgrades the application and starts the daemon again.

The problem is, that the redeploymyapp script needs to be executed by the user myapp, while MyPortal is running as www-data.

What is te best way to solve this problem?

I have a server certificate from CACert.org since two years. I have added CACert's root certificate to my browser. Everything worked fine, until my certificate expired. So I renewed my certificate on CACert.org and updated my .crt file on the server. But now I get sec_error_untrusted_issuer on the browser. But why? The issuer didn't change.

I have a hard disk containing a TrueCrypt volume on /dev/sdc. It is formated with NTFS. I am running Ubuntu 9.4.

To mount the volume I tried this:

 sudo truecrypt -t -k "" --protect-hidden=no /dev/sdc /mnt/data

After providing the correct password I get the following error:

Error: $LogFile indicates unclean shutdown (0, 0)
Failed to mount '/dev/mapper/truecrypt1': Operation not supported
Mount is denied because NTFS is marked to be in use. Choose one action:

Choice 1: If you have Windows then disconnect the external devices by
          clicking on the 'Safely Remove Hardware' icon in the Windows
          taskbar then shutdown Windows cleanly.

Choice 2: If you don't have Windows then you can use the 'force' option for
          your own responsibility. For example type on the command line:

            mount -t ntfs-3g /dev/mapper/truecrypt1 /mnt/data -o force

    Or add the option to the relevant row in the /etc/fstab file:

            /dev/mapper/truecrypt1 /mnt/data ntfs-3g force 0 0

I think, I need to pass the force mount-option somehow to the mount command. But how? The following does not work:

sudo truecrypt -t -k "" --protect-hidden=no --mount-options="-o force" /dev/sdc /mnt/data
Error: Unknown option: -o force