You want to set the default timezone for MySQL using my.cnf configuration file. But MySQL unable to start and the error log says:
Fatal error: Illegal or unknown default time zone 'NAMED_TIMEZONE'
Do not use named timezone unless you had timezone data populated on your mysql database. Instead use an offset relative to the UTC e.g: '+07:00' or '-04:00'.
Default Xenserver 6.2 root partition is 4GiB that's very small. So I want to separate the /tmp and swap to other partition in this case a LVM volume. The bad news is LVM volumes does not activate on boot. So entries in /etc/fstab which relies on LVM would fail and the boot process got stuck since the system would try to do some file system checking on every partition listed.
/etc/rc.sysinit around line 487 to 489. Take a look into these lines:
#if [ -x /sbin/lvm.static ]; then # action $"Setting up Logical Volume Management:" /sbin/lvm.static vgchange -a y --ignorelockingfailure #fiThat's the problem, the lines which activate the LVM volume is commented. That's why we ended up with the problem. Now just uncomment those lines and save the file. But make sure you made a copy of it. Reboot the server and all LVM volumes should be detected on boot. Here's an example of my XenServer custom partition scheme:
LABEL=root-mterkkri / ext3 defaults 1 1 #/var/swap/swap.001 swap swap defaults 0 0 none /dev/pts devpts defaults 0 0 none /dev/shm tmpfs defaults 0 0 none /proc proc defaults 0 0 none /sys sysfs defaults 0 0 /opt/xensource/packages/iso/XenCenter.iso /var/xen/xc-install iso9660 loop,ro 0 0 /dev/mapper/VG--XEN01-Dom0--TMP /tmp ext2 defaults,noexec,nosuid,nodev 1 2 /dev/mapper/VG--XEN01-Dom0--SWAP swap swap defaults 0 0 /tmp /var/tmp none rw,noexec,nosuid,nodev,bind 1 2
Without having to use usb-modeswitch switching the USB modem can be done easily. In this example I use USB CDMA modem with vendor ID 201e and product ID 1023 (when detected as CD-ROM storage) and product ID 1022 (when detected as USB modem or USB storage).
dmesg and lsusb commands. Make sure running these commands as root.
The Wifi ad-hoc network configuration that will be created for this task are composed from the following devices:
The more recent driver for TP-Link TL-WN723N can be found on https://github.com/lwfinger/rtl8188eu. This new driver address problem for kernel 3.8+. Do not forget to copy the firmware file rtl8188eufw.bin to /lib/firmware/rtlwifi/. Failed to do so, you might can not bring the device up.
I just bought a nano wireless adapter from TP-Link, the TL-WN723N. But my Xubuntu 12.04 did not recognize it, well that sucks. But thanks to this guy he made the driver for it: https://github.com/gleb-chipiga/rtl8188eu.
$ mkdir -p /tmp/tp-link && cd /tmp/tp-link $ git clone https://github.com/gleb-chipiga/rtl8188eu $ cd rtl8188eu $ make $ CURRENT_KERNEL=$( uname -r ) $ sudo cp 8188eu.ko /lib/modules/$CURRENT_KERNEL/kernel/drivers/net/wireless/ $ sudo depmod -a $ sudo modprobe 8188eu $ ip link showThe wireless adapter should be detected, no need to reboot.
To remove leading and trailing whitespace from a subset of strings in a shell we can use sed.
$ echo ' #FOO# ' | sed -e 's/\s*$//' -e 's/^\s*//' #FOO#
# Function to trim leading and trailing spaces
trim() {
# Accept input from argument or STDIN
# So you can do both:
# $ echo ' #FOO# ' | trim
# or
# $ trim ' #FOO# '
local STRING=$( [ ! -z "$1" ] && echo $1 || cat ; )
echo "$STRING" | sed -e 's/^\s*//' -e 's/\s*$//'
}
Now it can be used to trim a string both from argument or standard input.
$ echo ' #FOO# ' | trim #FOO# $ trim ' #FOO# ' #FOO#
Getting network interface name using IP address could be accomplished by issuing:
$ ip addr show | grep "192.168.1.2" | awk '{print $7}'
or another alternative:
ifconfig | grep -B 1 "192.168.1.2" | head -n1 | awk '{print $1}'
Both command would output the name of interface such as eth0, eth1, etc.
I have LVM partition reside on my external hard drive which connected trough USB. Here's the output before I unplug the device.
$ pvs PV VG Fmt Attr PSize PFree /dev/maxtor1-40g lvm2 a- 37.27g 37.27g /dev/sde5 XENVG lvm2 a- 125.78g 121.78gWhen I unplug and plug the device I always got I/O error like this:
$ pvs /dev/dm-0: read failed after 0 of 4096 at 0: Input/output error /dev/dm-0: read failed after 0 of 4096 at 4294901760: Input/output error /dev/dm-0: read failed after 0 of 4096 at 4294959104: Input/output error /dev/dm-0: read failed after 0 of 4096 at 4096: Input/output error PV VG Fmt Attr PSize PFree /dev/maxtor1-40g lvm2 a- 37.27g 37.27g /dev/sdd5 XENVG lvm2 a- 125.78g 121.78gWell that sucks since it would become unmountable. The LVM still pointing to the old /dev/sde5 that's why the error comes.
To prevent device name changes from time to time i.e: /dev/sdc to /dev/sdd and so on a corresponding udev rules need to be created. The first step to dive into udev configuration is getting information from the device.
When having multiple gateway it is very useful know which route is used by particular address. So we can know if the routing is work as expected. For this task we can use ip route get command.
ip route get 8.8.8.8
8.8.8.8 via 192.168.42.129 dev usb0 src 192.168.42.243
cache
If you want backup entire partition the dd is a very handy tool. It let you create a snapshot of the partition and quickly restore it if you need to. No need to worry about timestamps, ownership, permissions, links, etc.
I'm pretty shocked Windows comes with built-in quiet powerful command line tools for port forwarding. The name is netsh. Let say we want to redirect all incoming traffic to IP 1.2.3.4 port 80 to IP 1.2.3.4 port 8080.
prompt> netsh interface portproxy add v4tov4 listenport=80 listenaddress=1.2.3.4 connectport=8080 connectaddress=1.2.3.4
I came into situation where I need to pass some string to Pen Editor instance. The problem is the string is already encoded to HTML entities by PHP's htmlentities(). So, when I have value like This is <strong>strong</strong> element. The Pen editor instance convert it into:
Instead of this:
The solution is pretty dead simple just inject the string into textarea element and call the value property to get the content instead of innerHTML.
function decodeHtml(html){
var txt = document.createElement("textarea");
txt.innerHTML = html;
return txt.value;
}
If your string already came from textarea like in my case then you don't event need to create a single function.
What I want to achieve is like picture below.
h2.bottom {
display: table-cell;
vertical-align: bottom;
height: 60px; /* it's better to make it static */
line-height: 30px;
width: 400px; /* only as example */
}
Some devices like USB modem get stuck when it failed to connect and just hang up forever when trying to dial a number. The solution is unplug and plug it again, weird but it works. But seriously, that is not "a geek way". Rather than plug/unplug we could do it via shell to send the device "on" or "off" signal.
lsusb. Here's example of output in my system, make to sure run as root.
$ lsusb Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 04f2:b290 Chicony Electronics Co., Ltd Bus 001 Device 009: ID 0cf3:3005 Atheros Communications, Inc. AR3011 Bluetooth Bus 002 Device 018: ID 201e:1022 <-- WE WANT TO SEND SIGNAL TO THIS DEVICE Bus 002 Device 016: ID 03f0:ae07 Hewlett-Packard Bus 002 Device 012: ID 0458:00ee KYE Systems Corp. (Mouse Systems)
Simulating the health of services can be pain if we should install and turn them on/off the real services such HTTP Server, SSH Server, FTP, etc one-by-one on each VM. In this experiment I just faking 2 services which are: HTTP and SSH. Based on this simple topology we would end up with:
This should be applicable to real world (physical devices) not just virtualized environment. The topology is simple:
+----------------------------+
| The Host |
| -------- |
| Router |
+----------------------------+
| |
+-----+ +-----+
192.168.1.1 | br0 | | br1 | 192.168.1.9
+-----+ +-----+
| |
Mask: 192.168.1.0/29 | | Mask: 192.168.1.8/29
+--------------+ +----------+
| | |
| | |
+--------------+ | +---------------+
| VM 1 | +----+ | VM 3 |
| 192.168.1.2 | | | 192.168.1.10 |
+--------------+ | +---------------+
+--------------+
| VM 2 |
| 192.168.1.3 |
+--------------+
Suppose I already have rules for iptables like this:
$ iptables -L FORWARD -n -v --line-numbers Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) num pkts bytes target prot opt in out source destination 1 228 13794 ACCEPT all -- vmbr0 ppp0 192.168.1.10 0.0.0.0/0 2 337 28308 DROP all -- vmbr0 ppp0 0.0.0.0/0 0.0.0.0/0I want to insert my new rule between them (number 1 and 2). Here's how to do it:
$ iptables -I FORWARD 2 -i vmbr0 -o ppp0 -s 192.168.1.11 -j ACCEPTiptables insertion rules sounds something like "Insert it before number {X}". So in my case I need to put it before number 2 (-I FORWARD 2). Take a look to the result.
$ iptables -L FORWARD -n -v --line-numbers Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) num pkts bytes target prot opt in out source destination 1 228 13794 ACCEPT all -- vmbr0 ppp0 192.168.1.10 0.0.0.0/0 2 0 0 ACCEPT all -- vmbr0 ppp0 192.168.1.11 0.0.0.0/0 3 342 28728 DROP all -- vmbr0 ppp0 0.0.0.0/0 0.0.0.0/0
Two user space tools used for creating bridge networking in linux are tunctl and brctl. tunctl used for simulating the network or link layer device and brctl for configuring them.
tunctl -t vtap01 -u myuser ip link set up dev vtap01 # or ifconfig vtap01 up
brctl addbr vbr01 brctl addif vbr01 vtap01
ip link set up dev vbr01 ip addr add 192.168.1.1/30 dev vbr01 ip route add 192.168.1.0/30 dev vbr01or it could be written as:
ifconfig vbr01 up ifconfig vbr01 192.168.1.1 netmask 255.255.255.252 route add -net 192.168.1.0 netmask 255.255.255.252 dev vbr01The host at 192.168.1.2 should be able to ping host 192.168.1.1 (via bridge).
To test a generated ssh private/public key-pair without having to connect to a SSH server we can use ssh-keygen. Here's the example:
# ssh-keygen -y -f /location/of/the/private-keyReferences
Make sure running the iptables command as root. Example below shows how to block traffic coming from IP 1.2.3.4.
# iptables -I INPUT -s 1.2.3.4 -j DROPTurn on some logging on those rule, we insert it at line two. Assuming the first iptables command was the at line one.
# iptables -I INPUT 2 -s 1.2.3.4 -j LOG --log-prefix "Dropped an As*hole"References