Sometimes it is needed to extend the size of the disk which is used by VirtualBox.

To do this, you have to extend physical size of the disk image file. For example if you have disk file named WindowsC.vdi with 25 GB of size and you want to make it 50 GB, locate the image file and run the following command:

$ VBoxManage modifyhd Win7.vdi --resize 50000

If you got an error like this:

VBoxManage: error: Cannot register the hard disk 'WindowsC.vdi' {114b110c-65bd-4088-b3e1-7770bf39675d} because a hard disk 'WindowsC.vdi' with UUID {114b110c-65bd-4088-b3e1-7770bf39675d} already exists

you have to give disk image parameter by its uuid value which shown in error message:

$ VBoxManage modifyhd 114b110c-65bd-4088-b3e1-7770bf39675d --resize 50000
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%

After that, you have to start your virtual machine and extend the partition on that disk and resize the filesystem. This procedure depends on the operating system and filesystem in use.

In GUI by Debian User about 1 month ago 0 Comment

Java Network Launching Protocol (JNLP) files describes how to launch Java Web Start applications.

To execute a jnlp file, you need javaws binary which you can install with:

$ sudo apt-get install icedtea-netx

After that, it is simple to execute a jnlp file like that:

$ javaws filename.jnlp

You can also install icedtea-plugin package to integrate with web browser:

$ sudo apt-get install icedtea-plugin

Please note that, this plugin uses NPAPI and Google Chrome dropped support for NPAPI starting from version 35 on Linux and Mac. It will be dropped on Windows versions too. You need to run in console for this case.

See also: Javaws trusted.certs error fix

Tags: jnlp java chrome
In Database by Uğur Engin about 1 month ago 0 Comment

MySQL 5.5.8-linux2.6 setup problems in RHEL6.x/CentOS6.x distributions and quick fixes:

Problem 1:

/etc/init.d/mysql: line 256: my_print_defaults: command not found

Solution:

find /usr/local/mysql -name "my_print_defaults"
cp my_print_defaults /usr/bin/

Problem 2:

Couldn't find MySQL server (./bin/mysqld_safe)

Solution:

Open /usr/local/mysql/support-files/mysql.server script file then replace the line 

"basedir="

to

"basedir=/usr/local/mysql"

Tags: mysql 5.5.8
In Kernel by Murat Demirten 2 months ago 0 Comment

There are some cases in which you couldn't reboot a Linux system with reboot command or alternatives. If you have this problem and you don't have physical access to server, it is also possible to simulate pressing hardware reset button with the help of sysrq support in kernel.

To reboot the system through this magic interface, you need to activate sysrq first because it is disabled by default on all modern Linux distributions:

echo 1 > /proc/sys/kernel/sysrq

After that you can send b trigger to reboot system immediately like that:

echo b > /proc/sysrq-trigger

Please note that, rebooting with this method results to some data being lost. So, this method must be used only if there are no other chance to reboot system.

In Shell by Murat Demirten 2 months ago 0 Comment

Sometimes you may want to send binary data to a TCP or UDP connection. You can send text data to a TCP port with telnet command but it doesn't work for binary streams. There are some other alternatives which you can use like netcat or socat but it is also possible to send any data from TCP or UDP with just using bash shell's internal functionality. For example to send text data to 192.168.2.5's port 80 you can use:

$ echo "GET / HTTP/1.0" > /dev/tcp/192.168.2.5/80

or to send 160 bytes of a binary data to port 9000:

$ dd if=binary.dat bs=160 count=1 > /dev/tcp/192.168.2.5/9000

it is also possible to use udp too:

$ dd if=binary.dat bs=160 count=1 > /dev/udp/192.168.2.5/9000

Please note that, there is no /dev/tcp or /dev/udp folder exists in the system, this redirection mechanism is a feature of the bash shell itself.

In Networking by Debian User 2 months ago 0 Comment

If you're using vsftpd with chroot local user option and write enable like this:

write_enable=YES
chroot_local_user=YES

and you're getting following error when you log-in through ftp:

500 OOPS: vsftpd: refusing to run with writable root inside chroot()

you can fix the problem with adding following line to /etc/vsftpd.conf and restart the vsftpd service:

allow_writeable_chroot=YES

Tags: vsftpd chroot
In Database by Debian User 2 months ago 0 Comment

In a MySQL master-slave replication setup, if relay log files corrupted on the slave server's filesystem replication status becomes as:

  • Slave_IO_Running    => Yes
  • Slave_SQL_Running => No
  • Last_SQL_Errno       => 1594

If you have the same problem you can fix the replication with following steps:

  1. Check the slave status output and save the values of Relay_Master_Log_File and Exec_Master_Log_Pos variables:

    > SHOW SLAVE STATUS\G
    ...
      Relay_Master_Log_File: mysql-bin.000278
        Exec_Master_Log_Pos: 58392316
    ...

  2. After that stop the slave node:

    > STOP SLAVE;

  3. Reset replication (removes all the binlogs after the replication stop point)

    > RESET SLAVE;

  4. Change the master_log_file and master_log_pos variables of current replication setup with the values you save on first step like that:

    > CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000278', MASTER_LOG_POS=58392316;

  5. Start the replication again:

    > START SLAVE;

Everything should be ok.

In Database by Debian User 3 months ago 0 Comment

When you want to start multiple MySQL instance on the same server or you already have some other services which also heavily depends on asynchronous io framework in Linux, you may get following error on MySQL startup:

InnoDB: Warning: io_setup() failed with EAGAIN

There are two ways to fix this problem.

First solution is you can disable native asynchronous io support in InnoDB storage engine with putting following configuration in [mysqld] section of your my.cnf file:

innodb_use_native_aio = 0

But you will also loose some performance because of the aio disabled.

Second solution is, you can increase the maximum number of asynchronous request limit in kernel. Most distributions use default value of 65536 which you can see with following command:

cat /proc/sys/fs/aio-max-nr

You can set this number to 500000 or even more with:

echo 500000 > /proc/sys/fs/aio-max-nr

or it is better to make changes permanent with adding following lines to /etc/sysctl.conf or /etc/sysctl.d/XXX.conf file:

fs.aio-max-nr = 500000

Tags: mysql aio innodb
In Tools by Turker Sezer 3 months ago 0 Comment

Rygel is the one of the most popular DLNA softwares on Linux. It is a home media solution that allows you to easily share audio, video and pictures to other devices.

Rygel configuration is very simple except two tricky points. If you can't see all folders which you shared, follow instructions below.

Before we start to share our media files over network using rygel, we have to edit few lines in config file. Rygel config file is in ~/.config/rygel.conf path.

  • Select Folders to Share

We will list all folder names which we want to share as semicolon-seperated in uris parameter in [MediaExport] section. We don't need to escape special characters or spaces.

[MediaExport]
...
...
uris=/mnt/D/sample-folder/NEW;/mnt/D/sample folder/Videos;

  • Disable Tracker Plugin
Rygel disables MediaExport plugin which we use to share user-selected folders if Tracker plugin is enabled. So you can see only default pictures, videos and music folders as shared instead of user-defined folders. To disable Tracker plugin, we will change enabled parameter in [Tracker] section as False.

[Tracker]
enabled=false

Now we can run rygel command, and access all shared folders from other devices.

If you have a delay about 10-15 seconds when mounting shared NFS folders, check logfiles (/var/log/syslog, /var/log/messages) for a log like this:

RPC: AUTH_GSS upcall timed out

If you can see similar logs, your nfs mounts delayed by the Kerberos authentication on server side. If your NFS server in a network which needs Kerberos authentication, you have to set NEED_GSSD=yes in /etc/default/nfs-common file. After reboot, mount delays will be disappear.

But, most of the time you're not in a Kerberos enabled network or you don't need Kerberos authentication mechanism in your NFS server. If so, you have to blacklist rpcsec_gss_krb5 Linux kernel module. To do this create a file named /etc/modprobe.d/blacklist-nfs-gss.conf and add following line into that file:

blacklist rpcsec_gss_krb5

After reboot, you can mount without any delays.

Tags: nfs rpc