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MySQL

MySQL: unattended Percona Server 5.7 installation

Percona Server 5.7 needs slightly different answers passed to debconf-set-selections to allow unattended / silent installation:

MySQL

MySQL: split whole database dump into separate databases

If you have dumped all MySQL databases into one file (mysqldump --all-databases), you may have issues restoring a single database from that file. You can use awk to split the whole database dump into separate databases. * first save this script * and then run it against all_dbs.sql file:

MySQL

MySQL: Converting all tables in all databases from MyISAM to InnoDB

With MySQL, for most use cases, InnoDB is a much better database engine than MyISAM. If you have plenty of databases with tables in MyISAM format which you'd like to convert to InnoDB, here is a bash script which will do it. The script only converts MyISAM tables, and will

MySQL

MySQL: connecting to different ports on localhost

If you want to use mysql command to connect to MySQL server running on localhost, but on nonstandard port (not 3306), you may notice that whatever port you specify, it will connect you to the default MySQL server running on port 3306: This is because if you specify "-h localhost"

MySQL

MySQL: changing ROW FORMAT to DYNAMIC or COMPRESSED

f you've changed your database properties to use innodb_large_prefix = 1 and innodb_file_format = Barracuda in my.cnf as below: you may want to convert all your existing tables to use DYNAMIC or COMPRESSED ROW_FORMAT. For a single table, you need to run the following: To convert

MySQL

MySQL: avoiding "Waiting for table metadata lock" when executing "ALTER TABLE"

If you're running a busy database, the chances are that a ALTER TABLE statement executed will not really work, you will end up with MySQL processlist full of "Waiting for table metadata lock" - including your original ALTER TABLE statement, MySQL processlimit will be reached, and your website/system will

PostgreSQL

PostgreSQL: create a user with password and assign it to a database

To create a database user in PostgreSQL, do: Then, to create a database and assign our user to it: To verify - try connect using a wrong password: This is connecting with a good password:

Nginx

Nginx: 413 Request Entity Too Large

If you're seeing HTTP 413 "Request Entity Too Large" errors in your nginx logs, most likely this is caused by file uploads larger than allowed by nginx. To change it, add a larger client_max_body_size value to your nginx config. By default, the value is 1 megabyte. To

Embedded

Running Debian on Thecus n5200

It's rather easy to install any Linux of your choice on Thecus n5200 or n5200 Pro: it's a normal, x86-based PC! By default, Thecus ships n5200 with a 64 MB flash disk, and 256 MB RAM. The easiest way to install a full-flavoured Linux is to: * open your Thecus n5200

Embedded

Running Debian on Thecus n4100

Installation Installing is very similar to installing Debian on Thecus n2100 - see http://david.thg.se/n2100/. You will need a serial port, and a tftp server. Note that there is no Debian installer for Thecus n4100, so n2100 installation instructions from cyrius.com will not work. alternative installation

Embedded

Running Debian on Freecom FSG-3

Freecom FSG-3 is a small device with these specs: * Intel IXP425/IXP422 (ARM) CPU, running at 266 MHz * 64 MB RAM * 1 - WAN port and 3 - LAN ports * 4 USB ports * 1 eSATA port * HDD, ranging from 80 GB to 500 GB (depending on model) If the original

Embedded

Running Debian on ASUS WL-500W

This initial page is based on Running_Debian_on_ASUS_WL-500G_deluxe. Please bear in mind this page is under construction and depends also on other enthousiasts who contribute to make this page in final stage. It would be nice to see detailed instructions to get the wireless to work

Embedded

Running Debian on ASUS WL-500G deluxe:Additional hardware

Go back to the main "Running Debian on ASUS..." page. USB cameras Philips pwc webcams WL-500gP works with Philips webcams using pwc module. I did transcode a live stream using vlc and it worked fine. Wireless So far, it is not possible to use Broadcom mini-PCI. I tried two alternatives,

Embedded

Running Debian on ASUS WL-500G deluxe

You can run Debian (mipsel port) on ASUS WL-500g Deluxe, ASUS WL-500g Premium, ASUS WL-700gE, Linksys WRTSL54GS (and probably on similar, mipsel-based routers). See also a separate page for running Debian on ASUS WL-500W. ASUS WL-500g Deluxe is a small router with 200 MHz CPU, 32 MB RAM, 5 ethernet

Short tips and fixes

“Error: queue file write error” with Postfix and Amavis

If you’re using Postfix and Amavis, you may be seeing “Error: queue file write error”, especially with larger than usually email rates. Here is what you can do to get rid of them. If you’re getting too many of such messages: In main.cf, try adding: The default

Short tips and fixes

Viewing Linux console screens

If you want to see what's displayed on a certain Linux console screen remotely (i.e., you've left some programs running, or want to see the output of some program you started before etc.), log in to the machine you want and do: To see the first console (ctrl+atl+

Short tips and fixes

Using openssl instead of telnet to test HTTPS, POP3S connections

SSL is being used more often than plain text connections, so the usual testing with telnet may not work anymore. Fortunately, it's possible to use openssl command to test webservers, POP3S/IMAPS/SMTPS mailserver, FTPS servers etc. which use SSL. Testing HTTPS Testing SSMTP / SMTPS Or, to test TLS on

Short tips and fixes

Unprivileged lxc containers and open file limit problem

If you’re running unprivileged lxc containers, you will notice that some software fail to install or start. For example, you may have this kind of problem on Ubuntu, when trying to install mongo: The problem is the following line in /etc/init/mongod.conf: Because it’s an unprivileged

Short tips and fixes

Stale NFS handle

Ever rebooted your NFS server, just to find out that your NFS clients can’t access it any more, with an error message “Stale NFS file handle”? If this happened to you and you have your NFS server’s exports on a LVM volume, this means that you didn’t

Short tips and fixes

SSH exit codes

ssh from OpenSSH exits with the exit status of the remote command or with 255 if an error occurred. ssh2 on z/OS uses these exit codes:

Short tips and fixes

Source port routing

Sometimes, you may want some services (i.e. web) to be routed through a different interface. Here is a quick setup with some common problems. Assumptions: * 10.4.0.1 – your additional gateway, through which you only want to route web traffic (TCP port 80), * 10.4.0.2 – server

Short tips and fixes

Simple filesystem read/write tracing with /proc/sys/vm/block dump

Ever wondered what is hammering your disk so now and then, but couldn’t figure out with top / htop / iotop and similar? Annoying, but constant 100-200 kB/s writes? Or, simply blktrace was an overkill (or not supported by the kernel)? To debug, try this one (setting block_dump to

Short tips and fixes

Simple file sharing with Samba 4

A simple smb.conf for a read-only share in Samba 4 can look like below: You can mount it on Linux with: See also simple file sharing with Samba 3.

Short tips and fixes

Shell: finding the biggest file on the server

Finding the largest files (size) on the server:

Short tips and fixes

Scripting qemu / kvm monitor

There are some tasks in qemu / kvm monitor which could be scripted (i.e. like changing VNC password on demand). Here is how to do it with netcat and minicom. Using netcat (nc) Use this option: Then you can do: You can also use nc -U to access the unix