Simple setting of MySQL server for user's prefix

Few MySQL commands that I need:

• connect to database
  mysql --user=root mysql -p
• create db user 'paja' for connecting to localhost and also from outside
  CREATE USER 'paja'@'localhost' IDENTIFIED BY 'paja-password';
  CREATE USER 'paja'@'%' IDENTIFIED BY 'paja-password'; 
• grant privileges to create databases with prefix 'paja_'
  GRANT ALL PRIVILEGES ON `paja\_%` . * TO 'paja'@'localhost';
  GRANT ALL PRIVILEGES ON `paja\_%` . * TO 'paja'@'%';
• modify /etc/mysql/my.cnf by comment line
  bind-address           = 127.0.0.1
  that makes MySQL server listening only on localhost
• test connection from localhost and from different host
  mysql --user=paja -h localhost -p
  mysql --user=paja -h myhost.address -p

See http://dev.mysql.com/doc/refman/5.1/en/adding-users.html and http://stackoverflow.com/questions/2950054/let-mysql-users-create-databases-but-allow-access-to-only-their-own-databases

Perl modules

You have already met this
Can't locate PerlIO/gzip.pm in @INC (@INC contains: /etc/perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl .) at ...
because sometimes you have to install perl modules in non-standard folders (e.g. you are not root at the machine). How to solve it?

There is guide how to install perl module to specified folder
http://modperlbook.org/html/3-9-1-Installing-Perl-Modules-into-a-Nonstandard-Directory.html
In few steps:

• download modle from http://www.cpan.org/
• run

perl Makefile.PL PREFIX=/your/folder
make
make install

• export variable PERL5LIB to /your/folder/lib/perl/5.10.1

Now it should work.

To see what is in your @INC, run

perl -V
To test your module run
perl -Mmodule_name -e ''

disk information and format

It is quote common that you need information about disk. There are many commands (sometimes distribution depended) that can do that. Try following:

lshw -class disk
smartctl -i /dev/sda
hdparm -i /dev/sda
hwinfo --disk
ls /dev/disk/by-id
cat /proc/partitions

cat /proc/mdstat




To add new disk you just need

fdisk -l

parted /dev/sdb

(parted) mklabel GPT                                                      

(parted) mkpart primary 0% 100%                                           

(parted) quit

mkfs.ext4 /dev/sdb1

tune2fs -m 0 /dev/sdb1

Add line to /etc/fstab

identify problem

If something does not work first look at logs :
cat /var/log/syslog
dmesg

But there are not only these logs (see /var/log folder).

For hardware identify what was determined :
lsusb
lspci
lshal
lshw

There you easily find vendor or identification for hardware.

For software (run by command) try:
strace command


or use verbose output of command, often by:
command --verbose



For open files, see:
lsof

Mentioned utilities have many options, so try arguments. Use keywords from previous outputs to feed goog..

playing with linear raid and ext4

The goal is to create linear raid with ext4 array from 4 disks. Than add 5. disk and verify data.

Create linear raid from 4 disks
$ sudo mdadm -v --create /dev/md0 -l linear -n 4 /dev/sdb /dev/sdc /dev/sdd /dev/sde

Make ext4fs
$ sudo mkfs.ext4 /dev/md0

Mount array
$ sudo mkdir array
$ sudo mount /dev/md0 /media/array

Information about array
$ sudo mdadm --detail /dev/md0
$ cat /proc/mdstat

Set the system recognize the raid after the reboot
$ sudo echo 'DEVICES /dev/sdb /dev/sdc /dev/sdd /dev/sde' >> /etc/mdadm/mdadm.conf
$ sudo mdadm --detail --scan >> /etc/mdadm.conf

Upload test data, make md5 checksum
$ cd /media/array/
$ wget http://cdimage.debian.org/debian-cd/5.0.7/amd64/iso-cd/debian-507-amd64-netinst.iso
$ md5sum debian-507-amd64-netinst.iso
971ddace926fc3f7765f595da5cce223 debian-507-amd64-netinst.iso

Add 5. disk and resize filesystem
$ mdadm --grow --add /dev/md0 /dev/sdf
$ sudo resize2fs /dev/md0

Add device at /etc/mdadm/mdadm.conf and rescan (change list line)

Compare checksum
$ md5sum debian-507-amd64-netinst.iso
971ddace926fc3f7765f595da5cce223 debian-507-amd64-netinst.iso

Checksums are the same.

Add line to /etc/fstab and test reboot.

Sometimes there are problems with assemble, look in

cat /proc/mdstat


if there are not some dummy traits from one disk, that you can stop by

mdadm --stop /dev/md_d0


See also wiki

esxi managing from console

See also: Robert Chase page

It is easy to use console of ESXi server and do some managing from it.


Get all virtual machines
vim-cmd vmsvc/getallvms

Power off/on/reboot virtual machine with id 368
vim-cmd vmsvc/power.off 368
vim-cmd vmsvc/power.on 368
vim-cmd vmsvc/power.reboot 368

Get information about virtual machine with id 368
vim-cmd vmsvc/get.summary 368

Delete all snapshots
vim-cmd vmsvc/snapshot.removeall 368

Refresh datastore
esxcfg-nas -r

Delete and add nfs datastore back
esxcfg-nas -d back
esxcfg-nas -a back --host IPADDRESS --share DIRECTORY

Running processes
esxtop

Console screen
dcui

apache2 modules

List of loaded modules:
apache2ctl -t -D DUMP_MODULES

List of compiled modules:
apache2 -l

Apache2 version:
apache2 -v

Disable module:
a2dismod module_name

Enable module:
a2enmod module_name