Delete All Oracle User Objects

If you don't have system level access, and want to clean your oracle schema, the following sql will produce a series of drop statments, which can then be executed. Not all of them will execute - if you drop with cascade, dropping the PK_* indices will fail.

select 'drop '||object_type||' '|| object_name||  DECODE(OBJECT_TYPE,'TABLE',' CASCADE CONSTRAINTS;',';')from user_objects;

Confirm with:

select * from user_objects

Purge out the recyclebin if not needed:

purge recyclebin;

Resolve partial lvm logical volume

  1. Server rebooted during lvm snapshot and put volume group in inconsistent state.
    # vgs
      VG   #PV #LV #SN Attr   VSize   VFree
      vg0    1   3   0 wz--n- 229.66G 9.66G
      vg1    2   3   0 wz-pn- 279.46G 9.46G
    

    Note the "p" attribute in vg1 which put the group in partial mode.

  2. To resolve, I first vgreduce then re-created the volume group from a good known archive:

memcached on centos

Below is a summary of steps taken to get memcache support for php:

1. Install memcached and php-pear for pecl support to download and compile memcache for php.

    yum --enablerepo=epel install memcached php-pear
    pecl install memcache

2. Configure memcached (/etc/sysconfig/memcached) and start it up:

    chkconfig memcached on
    service memcached start

3. Create /etc/php.d/memcache.ini file with the below contents:

    extension=memcache.so

4. Reload apache and/or php-fpm processes:

    service httpd reload
    service php-fpm restart

5. Check with "php -i" or "phpinfo()" that memcache support is enabled.

6. Memcached listens to port 11211 by default. Status and stats:

    memcached-tool localhost:11211 display
    memcached-tool localhost:11211 stats

Adding utf-8 Byte Order Mark to file

#!/bin/bash
# add_bom.sh

FILE=$1

check() {
  if (( e = "$1" )); then
    echo "ERROR: $ACTION failed!!"
    exit $e
  else
    echo "INFO: $ACTION Success!!"
  fi
}

set_bom() {
    ACTION="Setting utf-8 BOM"
    # Detect if BOM already exists
    BOM=`sed -n '1{/^\xEF\xBB\xBF/p}' $FILE`
    if [ -z $BOM ]; then
        [ -f "$FILE" ] && /usr/bin/vim -e -s +"set bomb|set encoding=utf-8|wq" $FILE
        check $?
    fi
}

set_bom

To run, give the script the file name as argument:

sh ./add_bom.sh /path/to/file

Test the file via xxd, if the mark is present, the first line should output as below:

$ xxd </path/to/file
0000000: efbb bf...

OpenSSH SFTP chroot() with ChrootDirectory

(via www.debian-administration.org)

The upcoming version of OpenSSH (4.8p1 for the GNU/Linux port) features a new configuration option : ChrootDirectory. This has been made possible by a new SFTP subsystem statically linked to sshd.

sandboxed Python development environments with pythonbrew

(via suvashthapaliya.com)

As developers get started with a project, they prefer having total control over the development environment, as much as possible to perfectly match the deployment environment. The other strong requirement, especially in a team with mutiple developers would be to work on exactly replicated environments.

MySQL Database Restore

I've had to do mysql database restores based on lvm snapshot backups, one too many times... from damaging sql statements. So here is some notes from the last one for future reference:

* Prior to restore, make sure no writes are coming to the corresponding db schema.

* Restore the database schema from the daily archived snapshot:

service msyqld stop
mv /var/lib/mysql/db1 /var/lib/mysql/db1_old
cd /var/lib
tar -xzf /opt/bak/db/latest_db.tgz mysql/db1
tar -xvzf /opt/bak/db/latest_db.tgz mysql/snapshot.log
service mysqld start

Note: The above process is for database schema with MyISAM tables only, so just restoring the corresponding db folder was sufficient.

The snapshot.log file has the status of the master/slave replicated positions shown via "show master status\G" and "show slave status\G". Additionally, I also pipe in the file sizes of the mysql bin logs at the time the lvm snapshot was taken.

Once the database has been restored from the daily snapshot archive, begin restoring from the binary logs to bring the data up to date.

* Extract from bin log using position recorded in the snapshot.log file:

mysqlbinlog --database db1 --start-position=XXXXXX mysql-bin.[0-9]* >db1.sql

* Edit the db1.sql file and remove the unwanted transaction.

Note: If you do not have exact positions, you could playback the logs with an approximate start and end date in the below format:

--start-datetime="YYYY-MM-DD HH:MM:SS" --stop-datetime="YYYY-MM-DD HH:MM:SS"

* However, If duplicate error occurs, change "INSERT" to "INSERT IGNORE" or "REPLACE" to overwrite:

perl -pi -e 's/^INSERT /INSERT IGNORE /g' db1.sql

* Check to make sure that no other database schema is being used, if found you will have to remove those lines as well if playing back just a single schema:

grep -i "^use" db1.sql

* Run import:

mysql db1 <db1.sql

With that import, the datbase schema should be caught up and restored back to it's current state with the unwanted transaction/s removed.

Access VirtualBox Guest via Host

Go to VirtualBox Preferences and under "Network", add host-only network. This will add a new vboxnet0 interface, which comes up as "192.168.56.1/24"

In the Guest Settings, add the "Host-only" to a second "Network Adapter"

Once Guest boots up, assign a static IP to the second adapter.

For Debian based servers, edit /etc/network/interfaces and add the below, which should bring up the network upon reboot:

auto eth1
iface eth1 inet static
address 192.168.56.101
netmask 255.255.255.0

You should now be able to ping and ssh to the guest via the host server on the second interface.

Ensim Zone File Template

All bind templates are at "/usr/lib/opcenter/bind" location.

Modify "named_conf_zone.tmpl" file to allow for transfers adding in the IP addresses of secondary DNS.

Changing IP address of Ensim server

To change the IP address of an Ensim server, modify the following files replacing any instance of the old IP address with the new one:

/etc/hosts
/etc/resolv.conf
/etc/sysconfig/network
/etc/sysconfig/network-scripts/ifcfg-eth0
/etc/virtualhosting/namebased_ip_addrs
/etc/httpd/conf/httpd20_app.conf
/etc/virtualhosting/localnameserver
/etc/bind/options.conf.wp
/home/virtual/FILESYSTEMTEMPLATE/siteinfo/etc/resolv.conf

Reboot the server, then run the "NBDetectchanges"

/usr/local/bin/NBDetectchanges

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