A. Steps to create the logical volume..

List the current physical volumes. In this instance, were interested in a blank 20GB SATA – /dev/sdb. You can extend a logical volume by adding additional phyical volumes later.

fdisk -l
Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b5a0f

Device Boot Start End Blocks Id System
/dev/sda1 * 1 32 248832 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 32 2611 20719617 5 Extended
/dev/sda5 32 2611 20719616 8e Linux LVM

Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0×00000000

Format the entire disk as an LVM partition
fdisk /dev/sdb
n – new partition
p – primary
1 – partition number
Enter – First cylinder
Enter – last cylinder
t – change type
1 – our partition
8e – LVM
w – write

Do the same for any additional disks to be added to the volume group

Prepare the new partitions(s) for LVM:
pvcreate /dev/sdb1

Display the new physical volume:
pvdisplay

“/dev/sdb1″ is a new physical volume of “19.99 GiB”
— NEW Physical volume —
PV Name /dev/sdb1
VG Name
PV Size 19.99 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID 8dPHo4-Rztw-hOLJ-KW9M-hfjj-XwUJ-g3vyUr

Create a Volume Group
vgcreate wwwfiles /dev/sdb1

Display your Volume Group
vgscan
or
vgdisplay
— Volume group —
VG Name wwwfiles
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 1
Act PV 1
VG Size 19.99 GiB
PE Size 4.00 MiB
Total PE 5118
Alloc PE / Size 0 / 0
Free PE / Size 5118 / 19.99 GiB
VG UUID w6sdJY-9ehv-8XVE-7azw-WIQz-s9yD-XYyspc

Create a Logical Volume or two in the Group
lvcreate --name site1 --size 4G wwwfiles
lvcreate --name site2 --size 4G wwwfiles

Display the Logical Volumes
lvscan
or
lvdisplay
— Logical volume —
LV Name /dev/wwwfiles/site1
VG Name wwwfiles
LV UUID Lh2yxC-GjpH-RRzC-LG6r-m5h5-zK7A-7lvkYE
LV Write Access read/write
LV Status available
# open 0
LV Size 4.00 GiB
Current LE 1024
Segments 1
Allocation inherit
Read ahead sectors auto
– currently set to 256
Block device 251:3

— Logical volume —
LV Name /dev/wwwfiles/site2
VG Name wwwfiles
LV UUID KVfvbZ-ok5E-IINJ-mjAq-DSoj-7NrS-ojtADK
LV Write Access read/write
LV Status available
# open 0
LV Size 4.00 GiB
Current LE 1024
Segments 1
Allocation inherit
Read ahead sectors auto
– currently set to 256
Block device 251:4

We now need to add a filesystem to the Logical Volume:
mkfs.ext3 /dev/wwwfiles/site1

The Logical Volumes can now be mounted onto the system:
mkdir /var/www/site1
mount /dev/wwwfiles/site1 /var/www/site1
check df -h to make sure successful

To make the mount persistent, add a line to /etc/fstab:
/dev/wwwfiles/site1 /var/www/site1 ext3 rw,noatime 0 0

B. Enlarge a Logical Volume & filesystem

Unmount it:
umount /var/www/site1

Enlarge the Logical Volume:
lvextend -L5G /dev/wwwfiles/site1

Check the filesystem:
e2fsck -f /dev/wwwfiles/site1

Resize the filesystem:
resize2fs /dev/wwwfiles/site1

Remount & check successful:
mount /dev/wwwfiles/site1 /var/www/site1
df -h

C. Shrink a Logical Volume & filesystem

Unmount it:
umount /var/www/site1

Check the filesystem. Resizing is specified in blocks, so we need to calculate from this result, how many blocks to give it:
e2fsck -f /dev/wwwfiles/site1

Resize the filesystem:
resize2fs /dev/wwwfiles/site1 1048576

Shrink the Logical Volume:
lvreduce -L4G /dev/wwwfiles/site1

Remount:
mount /dev/wwwfiles/site1 /var/www/site1
check df -h to make sure successful

D. Adding another hard disk

Format the entire disk as an LVM partition:
fdisk /dev/sdc
n – new partition
p – primary
1 – partition number
Enter – First cylinder
Enter – last cylinder
t – change type
1 – our partition
8e – LVM
w – write

Prepare the new partitions(s) for LVM:
pvcreate /dev/sdc1

Add /dev/scc1 to our Volume Group:
vgextend wwwfiles /dev/sdc1

Check for the additional space with vgdisplay

E. Remove a disk

Move data off the disk to be removed:
pvmove /dev/sdb1 /dev/sdf1

Remove /dev/sdb1 from the Volume Group:
vgreduce wwwfiles /dev/sdb1

Verify with vgdisplay

Remove the Physical Volume:
pvremove /dev/sdb1

Verify with pvdisplay

*notes*

lvextend can be called in several ways
-L12G = sets to 12GB
-L+2G = adds an additional 2GB
-L+100%FREE = adds all of the remaining free space in the Volume Group

Enlarge a Logical Volume
lvextend -L5G /dev/wwwfiles/site1

Reduce a Logical Volume
lvreduce -L2G /dev/wwwfiles/site1

Delete a Logical Volume
lvremove /dev/wwwfiles/site1

Rename a Logical Volume
lvrename site1 site3

Delete a Volume Group
vgremove wwwfiles

Rename a Volume Group
vgrename wwwfiles files

Remove a physical volume
pvremove /dev/sdb1

2.11.1.24 – fixed IP of server1
2.11.1.25 – fixed IP of server2
2.11.1.30 – apache site1 (virtual IP)
2.11.1.31 – apache site2 (virtual IP)

Make sure both servers have a sensible hostname and ensure their hosts files relate to this:

etc/hosts
127.0.0.1 localhost
2.11.1.24 ubuntu-server-1.mydomain.com ubuntu-server-1
2.11.1.25 ubuntu-server-2.mydomain.com ubuntu-server-2

Set up SSH keys so that root can log onto each server. No passphrase is needed:

mkdir /root/.ssh
cd /root/.ssh
ssh-keygen -t rsa
chmod 600 id_rs*
scp id_rs* root@ubuntu-server-2:/root/.ssh
cat id_rsa.pub >> authorized_keys2
ssh root@ubuntu-server-2 "echo \`cat /root/.ssh/id_rsa.pub\` >> ~/.ssh/authorized_keys2"

Set up the fixed IP on each server in /etc/network/interfaces:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
address 2.11.1.24
netmask 255.0.0.0
gateway 2.3.1.18
broadcast 2.255.255.255
network 2.0.0.0

Restart networking and ensure connectivity is working:
/etc/init.d/networking restart

Install the HA stuff on both servers:
apt-get install heartbeat pacemaker

Install Apache on both servers and disable the startup scripts as pacemaker will be controlling the service:

apt-get install apache2
/etc/init.d/apache2 stop
chkconfig apache2 off

Add the virtual site IP’s to the apache configuration on both servers:

Listen 2.11.1.30:80
Listen 2.11.1.31:80

If you have a line “Listen 80″ without an IP, you will need to remove this.

Add the relevant virtualhost entries for your sites in /etc/apache2/sites-enabled on both servers

ServerAdmin webmaster@localhost
DocumentRoot /var/www



ServerAdmin webmaster@localhost
DocumentRoot /var/www2


This might be a good page to start with for testing:

<html><body><h1>Test</h1>
<p>This is the default web page for this server.</p>
<?
$hostname=`/bin/hostname`;
echo "Running on ".$hostname.$_SERVER['SERVER_NAME'];
?>
</body></html>

Add something like this to server1 and server2 /etc/heartbeat/ha.cf. The server its on will ignore its own IP:

logfile /var/log/ha-log
logfacility local0
udpport 694
keepalive 2
warntime 15
deadtime 12
initdead 30
ucast eth0 2.11.1.24
ucast eth0 2.11.1.25
node ubuntu-server-1 ubuntu-server-2
auto_failback on
respawn hacluster /usr/lib/heartbeat/ipfail
crm respawn

On both servers, edit /etc/ha.d/authkeys, add the following. Use a strong password/hash.
You can generate some MD5 by echo "lsdknfnlsd;skrwerkorkwprek" | openssl md5:

auth 1
1 md5 $1$shRyHw.b$hEMxuYID7wEsK1mvGq8

chmod 600 /etc/ha.d/authkeys

Start the heartbeat service on both servers. Make sure the log exists and check for errors:
/etc/init.d/heartbeat start

Install DRBD on both servers:

apt-get install drbd8-utils build-essential psmisc
chkconfig drbd off

vi /etc/drbd.d/r0.res with something like the following on both servers. Use a sensible shared key:

resource r0 {
protocol C;
syncer {
rate 4M;
}
startup {
wfc-timeout 15;
degr-wfc-timeout 60;
}
net {
cram-hmac-alg sha1;
shared-secret "RUBBERDUCK";
}
on ubuntu-server-1 {
device /dev/drbd0;
disk /dev/sdb;
address 2.11.1.24:7788;
meta-disk internal;
}
on ubuntu-server-2 {
device /dev/drbd0;
disk /dev/sdb;
address 2.11.1.25:7788;
meta-disk internal;
}
}

For further filesystems use r1.res r2.res etc. drbd0 becomes drbd1, also the port number must increment. 7788 becomes 7789. Probably a good idea to use a DRBD filesystem for the web app files, unless they are rarely updated, then rsync etc could be an option. In this example, I’m using a plain virtualbox emulated SATA disk. In reality using LVM might be a good idea.

Blank out the partition to be used for DRBD
dd if=/dev/zero of=/dev/sdb bs=1024k
drbdadm create-md r0

Do this again on the second server

/etc/init.d/drbd start

Run this on the primary server to sync the data (even though its currently empty)
drbdadm -- --overwrite-data-of-peer primary r0

It should take a little while, check progress with watch -n1 cat /proc/drbd

On the primary server, create an ext3 filesystem on the DRBD disk:

drbdadm primary r0
mkfs.ext3 /dev/drbd0

On both servers, install mysql

apt-get install mysql-server
service mysql stop
chkconfig mysql-server off

Mount MySQL data onto the DRBD disk on primary server:

mkdir /root/mysql_bak
cp -Ra /var/lib/mysql/* /root/mysql_bak/
rm -rf /var/lib/mysql/*
drbdadm primary r0
mount /dev/drbd0 /var/lib/mysql
cp -Ra /root/mysql_bak/* /var/lib/mysql/
chown mysql:mysql /var/lib/mysql
umount /var/lib/mysql
drbdadm secondary r0
ssh root@ubuntu-server-2 "rm -rf /var/lib/mysql/*"

Time to configure the resources:

crm configure edit

Replace the data with:

node $id="05a131a7-7f92-4442-be0f-73fa722f1bb4" ubuntu-server-1 \
attributes standby="off"
node $id="9d31841c-5537-4bc3-b2c2-bfa5021ef880" ubuntu-server-2
primitive apache2 lsb:apache2 \
op monitor interval="5s" \
meta target-role="Started"
primitive drbd_mysql ocf:linbit:drbd \
params drbd_resource="r0" \
op monitor interval="15s"
primitive fs_mysql ocf:heartbeat:Filesystem \
params device="/dev/drbd/by-res/r0" directory="/var/lib/mysql" fstype="ext3" \
op start interval="0" timeout="60" \
op stop interval="0" timeout="120"
primitive ip1 ocf:heartbeat:IPaddr2 \
params ip="2.11.1.30" nic="eth0:0"
primitive ip1arp ocf:heartbeat:SendArp \
params ip="2.11.1.30" nic="eth0:0"
primitive ip2 ocf:heartbeat:IPaddr2 \
params ip="2.11.1.31" nic="eth0:0"
primitive ip2arp ocf:heartbeat:SendArp \
params ip="2.11.1.31" nic="eth0:0"
primitive mysql ocf:heartbeat:mysql \
params binary="/usr/bin/mysqld_safe" config="/etc/mysql/my.cnf" user="mysql" group="mysql" log="/var/log/mysql.log" pid="/var/run/mysqld/mysqld.pid" datadir="/var/lib/mysql" socket="/var/run/mysqld/mysqld.sock" \
op monitor interval="30s" timeout="30s" \
op start interval="0" timeout="120" \
op stop interval="0" timeout="120"
group MySQLDB fs_mysql mysql \
meta target-role="Started"
group WebServices ip1 ip1arp ip2 ip2arp apache2 \
meta target-role="Started"
ms ms_drbd_mysql drbd_mysql \
meta master-max="1" master-node-max="1" clone-max="2" clone-node-max="1" notify="true"
location cli-prefer-MySQLDB MySQLDB 100: ubuntu-server-1
location cli-prefer-WebServices WebServices 100: ubuntu-server-1
colocation ip_with_arp inf: ip1 ip1arp ip2 ip2arp
colocation mysql_on_drbd inf: MySQLDB ms_drbd_mysql:Master
colocation web_with_ip inf: apache2 ip1 ip2
colocation web_with_mysql inf: apache2 MySQLDB
order arp_after_ip inf: ip1:start ip1arp:start ip2:start ip2arp:start
order fs-mysql-after-drbd inf: ms_drbd_mysql:promote fs_mysql:start
order mysql-after-fs-mysql inf: fs_mysql:start mysql:start
order web_after_ip inf: ip1arp:start ip2arp:start apache2:start
property $id="cib-bootstrap-options" \
dc-version="1.0.9-da7075976b5ff0bee71074385f8fd02f296ec8a3" \
cluster-infrastructure="Heartbeat" \
expected-quorum-votes="1" \
stonith-enabled="false" \
no-quorum-policy="ignore"
rsc_defaults $id="rsc-options" \
resource-stickiness="100"

Pay attention to the order. For example, you will want MySQL to start, after the MySQL filesystem has been mounted
Resource stickiness sets whether the resources should fail back if the primary server comes back online. 0 should fail back, whereas 100 should keep it on the secondary node, ready for a manual failback.
Location sets the preference server for the resource to run on
Colocation sets whether resources should always run on the same server.

Save the changes – this should automatically replicate to server2.

Things should now be up and running, run crm_mon to check status. It should look a little like:

============
Last updated: Thu Aug 25 11:38:59 2011
Stack: Heartbeat
Current DC: ubuntu-server-2 (9d31841c-5537-4bc3-b2c2-bfa5021ef880) – partition with quoru
m
Version: 1.0.9-da7075976b5ff0bee71074385f8fd02f296ec8a3
2 Nodes configured, 1 expected votes
3 Resources configured.
============

Online: [ ubuntu-server-2 ubuntu-server-1 ]

Resource Group: WebServices
ip1 (ocf::heartbeat:IPaddr2): Started ubuntu-server-1
ip1arp (ocf::heartbeat:SendArp): Started ubuntu-server-1
ip2 (ocf::heartbeat:IPaddr2): Started ubuntu-server-1
ip2arp (ocf::heartbeat:SendArp): Started ubuntu-server-1
apache2 (lsb:apache2): Started ubuntu-server-1
Resource Group: MySQLDB
fs_mysql (ocf::heartbeat:Filesystem): Started ubuntu-server-1
mysql (ocf::heartbeat:mysql): Started ubuntu-server-1
Master/Slave Set: ms_drbd_mysql
Masters: [ ubuntu-server-1 ]
Slaves: [ ubuntu-server-2 ]

You should now see your sites available at http://2.11.1.30 http://2.11.1.31

You should really consider using STONITH to ringfence a dodgy node. Stonith plugins exist for Dell DRAC / IBM RAS etc thesedays.

Some Useful commands:

crm – takes you into the crm console. This tab completes commands so is quite intuitive.
crm_mon – status monitoring
crm status – the same
crm configure edit – edit config
crm configure show – show config
crm (-F) resource move WebServices ubuntu-server-2 – force single resource/resourcegroup to another server
crm unmove Webservices – move resources back to primary

crm node standby ubuntu-server-1 – take node offline, resources will failover to other server
crm node online ubuntu-server-1 – bring node online
crm resource restart/start/stop apache2 – manage a resource (you cant use init scripts anymore!)

References:

http://library.linode.com/linux-ha/ip-failover-heartbeat-pacemaker-drbd-mysql-ubuntu-10.04

http://www.clusterlabs.org/wiki/Documentation#Howtos

The server packages to install are:
Ubuntu:
apt-get-install nfs-kernel-server nfs-common quota
RedHat:
yum install nfs-utils nfs-utils-lib quota

The client Packages are:
Ubuntu:
apt-get install nfs-common
RedHat:
yum install nfs-utils nfs-utils-lib

A few things to configure on the server:

/etc/hosts.allow
Any hosts listed here will be granted access to everything i.e
ALL: 2.11.1.2[4-5]
ALL: 192.168.1.*

or just NFS access:
portmap: 192.168.0.1 , 192.168.0.2
lockd: 192.168.0.1 , 192.168.0.2
rquotad: 192.168.0.1 , 192.168.0.2
mountd: 192.168.0.1 , 192.168.0.2
statd: 192.168.0.1 , 192.168.0.2

/etc/hosts.deny
Any hosts here will be denied access i.e
portmap: ALL
lockd:ALL
mountd:ALL
rquotad:ALL
statd:ALL
Doing an ALL: ALL would block other services such as SSH. Its a good idea to deny all hosts by default and explicitly list hosts in hosts.allow as any hosts not listed in allow or deny will be automatically allowed.

/etc/exports
Defines what will be shared and to who can be single IP, netgroup, CIDR, wildcard i.e
/home 192.168.0.1(rw) 192.168.0.2(rw)
/files *(rw,all_squash, subtree_check)
/home 192.168.0.0/255.255.255.0(rw)
/files *(rw,sync,no_subtree_check,anonuid=222,anongid=1001)

* = share to ALL allowed hosts
ro= read only
rw = read write
root_squash = (default) maps root requests to the anonymous user
no_root_squash = remote root user is root!
all_squash = all remote users become anonymous user
subtree_check / no_subtree_check = When subdirectories of filesystems are exported, the server must check that the tree is in the correct filesystem. Disabling has mild security implications but can improve performance.

If you make changes to exports later, run rpcinfo quota for NFS to re-read it.

Make sure the right services are running:
RedHat:
/etc/init.d/nfs start
/etc/init.d/portmap start

Ubuntu:
/etc/init.d/nfs-kernel-server start
/etc/init.d/portmap start

To connect from the client:

Make sure portmap is running:
/etc/init.d/portmap start

Add something like so to your /etc/fstab depending on your options
192.168.100.85:/home/myself /mnt/test nfs users,auto,rw 0 0
NAS:/files /files nfs users,auto,rw,sync,rsize=8192,timeo=14,wsize=8192,intr 0 0

mkdir /files
mount /files

Check the files have mounted correctly

*Notes*
NFS isn’t the most secure of things – run only over your local network/VPN/somewhere secure.
Firewalls:
Portmap – 111TCP/UDP
nfsd – 2049 TCP-UDP

statd,mountd,lockd,rquotad will generally float around the next available port from portmapper. You can bind to a specific port:

REDHAT
1. Find some free ports
2. Edit /etc/sysconfig/nfs
# NFS port numbers
STATD_PORT=10002
STATD_OUTGOING_PORT=10003
MOUNTD_PORT=10004
RQUOTAD_PORT=10005
LOCKD_UDPPORT=30001
LOCKD_TCPPORT=30001

UBUNTU
Edit /etc/default/nfs-common and add

STATDOPTS="--port 32765 --outgoing-port 32766"

Edit /etc/default/nfs-kernel-server and add

RPCMOUNTDOPTS="-p 32767"

Edit /etc/default/quota and add

RPCRQUOTADOPTS="-p 32769"

Create /etc/modprobe.d/local.conf with the contents

options lockd nlm_udpport=32768 nlm_tcpport=32768

Update /etc/services

# NFS ports as per the NFS-HOWTO
# http://www.tldp.org/HOWTO/NFS-HOWTO/security.html#FIREWALLS
# Listing here does not mean they will bind to these ports.
rpc.nfsd 2049/tcp # RPC nfsd
rpc.nfsd 2049/udp # RPC nfsd
rpc.statd-bc 32765/tcp # RPC statd broadcast
rpc.statd-bc 32765/udp # RPC statd broadcast
rpc.statd 32766/tcp # RPC statd listen
rpc.statd 32766/udp # RPC statd listen
rpc.mountd 32767/tcp # RPC mountd
rpc.mountd 32767/udp # RPC mountd
rcp.lockd 32768/tcp # RPC lockd/nlockmgr
rcp.lockd 32768/udp # RPC lockd/nlockmgr
rpc.quotad 32769/tcp # RPC quotad
rpc.quotad 32769/udp # RPC quotad

Update your firewall accordingly and restart NFS. You may find this doesnt work on your distro as some modules may be compiled in the kernel. rpcinfo -p will list the port numbers being used – do a google if its not going to plan!

You will probably want to make sure that the owner of the files on the fileserver and the user(s) accessing them exist on all systems and have the same UID’s.

Random error I had with NFSv4 was mounting with a UID and GID of 4294967294 even though the system UID’s matched up correctly. If you can live with v3 then just add -o vers=3 to your mount command. The better fix is:

edit /etc/idmapd.conf and set Domain on server and client to the “localdomain”

[General]
Domain = localdomain
[Translation]
Method = nsswitch
change the /etc/default/nfs-common file (on both your server and client): set NEED_IDMAPD= yes

start and enable idmapd service on both servers

# Allow outgoing traffic and disallow any passthroughs

iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

# Allow traffic already established to continue

iptables -A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT

# Allow web services

iptables -A INPUT -p tcp –dport ssh -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport domain -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport ftp -i eth0 -j ACCEPT
iptables -A INPUT -p udp –dport ftp -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport ftp-data -i eth0 -j ACCEPT
iptables -A INPUT -p udp –dport ftp-data -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 80 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 443 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 25 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 465 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 110 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 143 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 585 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 993 -i eth0 -j ACCEPT
iptables -A INPUT -p tcp –dport 995 -i eth0 -j ACCEPT

# Allow local loopback services

iptables -A INPUT -i lo -j ACCEPT

# Allow pings

iptables -I INPUT -p icmp –icmp-type destination-unreachable -j ACCEPT
iptables -I INPUT -p icmp –icmp-type source-quench -j ACCEPT
iptables -I INPUT -p icmp –icmp-type time-exceeded -j ACCEPT

get the current system time:
date

Schedule at to run a command 5 minutes from now:
at -m 13:50
service iptables stop
ctrl-d

Now, make those firewall changes that you need to, without worrying!

If all goes belly up, at will stop the firewall in 5 mins.

If all goes well, you can cancel the at command:
atq
atrm 2

/numptyness

Connectbot is a great SSH client for the Android. It is fully functional, supporting SSH keys and copy/paste etc.

For Windows RDP connections, I found PocketCloud to be the nicest to use free app, but at the time of writing there was a keyboard bug on Samsung handsets. Remote RDP Lite does the same thing in a less elegant way.

K-9 Mail + APG – The standard Android mail client isn’t too impressive. K-9 mail bring much more functionality and usability, whilst adding APG allows you to manage GPG/PGP encrypted emails.

net swiss tools – A small networking utility suite allowing you to quickly ping, check ports, traceroute etc.

andftp – A pretty decent FTP client that also support SCP, FTPS etc.

Generally I get my nagios monitoring alerts via email, but nagdroid is quite a cool little nagios monitoring app for the android. It’s not great looking, but runs as a service and pops up whenever there is an alert.

Basics:

Start screen:
screen

Create new screen window:
CTRL + A + C

Run a command in a new screen window:
CTRL + A + [command]

Flip to the nextscreen:
CTRL + A + N

Flip to the previous screen:
CTRL + A + P

Detach screen (send screen to the background and return to your shell)
CTRL + A + D

Show screen sessions:
screen -ls
There is a screen on:
21970.pts-0.ct-1565 (Detached)

Re-attach to a detatched screen:
screen -r [session]
screen -r 21970.pts-0.ct-1565 in this case

If your screen is still attached you must detatch it before being able to re-attach:
screen -d [session]

To Exit from screen back to your shell, just:
exit
[screen is terminating] will let you know your back.

To install the JDK

yum install -y jpackage-utils
wget http://cds.sun.com/is-bin/INTERSHOP.enfinity/WFS/CDS-CDS_Developer-Site/en_US/-/USD/VerifyItem-Start/jdk-6u14-linux-x64-rpm.bin?BundledLineItemUUID=KxWJ_hCuwSUAAAEvTWRZB8TT&OrderID=WeuJ_hCuedUAAAEvLGRZB8TT&ProductID=tPxIBe.oz2IAAAEhmh0zLjfT&FileName=/jdk-6u14-linux-x64-rpm.bin
chmod +x jdk-6u14-linux-i586-rpm.bin
./jdk-6u14-linux-i586-rpm.bin

To install the JRE

If you dont have a build environment yet, create one (non-root user!) For example:

yum install -y rpm-build gcc gcc-c++ redhat-rpm-config
useradd builder
su - builder
vi ~/.rpmmacros
add the following:
%_topdir /home//rpmbuild
%_tmppath %{_topdir}/tmp
mkdir -p ~/rpmbuild/{SOURCES,SRPMS,SPECS,RPMS,tmp,BUILD}
cd ~/rpmbuild/SOURCES
Download Sun JDK 1.6 update 14 jdk-6u14-linux-i586.bin or jdk-6u14-linux-x64.bin
wget http://cds.sun.com/is-bin/INTERSHOP.enfinity/WFS/CDS-CDS_Developer-Site/en_US/-/USD/VerifyItem-Start/jdk-6u14-linux-x64.bin?BundledLineItemUUID=cDCJ_hCudtMAAAEvQWRZB8TT&OrderID=WeuJ_hCuedUAAAEvLGRZB8TT&ProductID=tPxIBe.oz2IAAAEhmh0zLjfT&FileName=/jdk-6u14-linux-x64.bin


cd ~/rpmbuild/
Download the nosrc.rpm from jpackage
wget wget http://mirrors.dotsrc.org/jpackage/6.0/generic/SRPMS.non-free/java-1.6.0-sun-1.6.0.14-1jpp.nosrc.rpm

Rebuild the packages:
rpmbuild --rebuild java-1.6.0-sun-1.6.0.14-1jpp.nosrc.rpm

exit to root user

yum install jpackage-utils
Make sure you install the java and devel package, otherwise alternatives wont configure 1.6 properly
yum --nogpgcheck localinstall java-1.6.0-sun-1.6.0.14-1jpp.x86_64.rpm java-1.6.0-sun-devel-1.6.0.14-1jpp.x86_64.rpm

Select the new version of java to use:

alternatives --config java

Confirm that the correct version of java is running:

java --version

If its wrong, check the symlink for /usr/bin/java
Also check the $JAVA_HOME variable
Restart tomcat or whatever is using Java, to make sure its using the new JVM.

/etc/yum.conf add the line:
tsflags=repackage

/etc/rpm/macros add the line:
(create this file if it doesnt exist)
%_repackage_all_erasures 1

Once this has been enabled, any install/update/erase you do through yum or RPM will save the roll back information, allowing you to easily roll back the transaction should something bad happen.

Examples:

rpm -Uhv –rollback ’14:00′
rpm -Uhv –rollback ’9 hours ago’
rpm -Uhv –rollback ‘december 12′
rpm -Uhv –rollback ‘yesterday’

Anyway, to start with a simple one, I signed into my wordpress account today and noticed that the site stats weren’t working with the following error:

Your WordPress.com account, xxx is not authorized to view the stats of this blog.

Simple fix: wordpress.com stats now seem to be integrated with jetpack. Disable the stats plugin, then install the jetpack plugin. You will need a wordpress.com account if you haven’t got one already.