Showing posts with label Administration. Show all posts

Monday, 15 February 2016

Running an NTP server in a VM using KVM

The setup

Having physical server pA, running VMs using KVM. One of theVMs (vA) acts as an NTP server. pA gets the time from vA and vA gets it from the Internet.

It's not a great idea to run an NTP server in a VM, but in this case there was need for it.

The problem

NTP server gets frequently out of sync.

If you use nagios, you may get errors like this:

SERVICE ALERT: pA;ntpd;CRITICAL;SOFT;4;NTP CRITICAL: Offset unknown

Both for the physical server and other servers that fetch the time from vA.

The reason

There's some guessing involved here, but this should be pretty accurate:

VM vA needs to correct its clock every now and then by slowing down or speeding up things per ntpd/adjtimex. As expected, this creates a small discrepancy between vA and pA, as now the physical server gets out of sync and needs to correct its time using vA's reference time.

Once vA attempts to correct its time, again by slowing down or speeding up its clock, this has a direct effect on vA, as vA's clock is now affected by pA's ongoing adjustment. This happens because KVM by default uses kvmclock as its clock source (the source that ticks and not the source that returns the time of the day).

This action sometimes causes pA's ntpd to get even more out of sync and may even make it consider its peers inaccurate and become fully out of sync.

The problem gets even worse if you have two ntp servers (vA and vB) running on two different physical servers (pA and pB), because the amount of desync between the two is mostly random. Assuming that all your servers, including pA and pB, fetch the time from vA and vB, the discrepancy between them will make them mark at least one of them as wrong, as the stratum of vA and vB does not permit such difference between their clocks.

You can see the above by looking at the falsetick result in ntpq's associations:

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 33082  961a   yes   yes  none  sys.peer    sys_peer  1
  2 33083  911a   yes   yes  none falsetick    sys_peer  1

Overall, the problem is that the physical servers will try to fix their clocks, thus affecting the clocks of the NTP servers running in VMs under them.

The solution

The problem is with the VMs using the kvmclock source. You can see that using dmesg:

$ dmesg | grep clocksource
Switching to clocksource kvm-clock

The way to disable this is to pass the "no-kvmclock" parameter to the kernel of your VMs. This will not always work though. The reason is that the kernel (at least the CentOS kernels) will panic very early in the boot process as it will still try to initialize the kvmclock even if it's not going to use it, and will fail.

The solution is to pass two parameters to your VM kernels: "no-kvmclock no-kvmclock-vsyscall". The second one is a bit undocumented, but will do the trick.

After that you can verify it through dmesg:

$ dmesg | grep Switching
Switching to clocksource refined-jiffies
Switching to clocksource acpi_pm
Switching to clocksource tsc

Example

Below is the output of a server running in such an environment. In this case the first ntp server (vA) runs with the extra kernel parameters and the other (vB) runs without them. The clock of the physical servers (pA and pB) was slowed down by hand using adjtimex in order to test the effect of the physical server's clock on the VM clocks. As you can see, this server is still in sync with vA and has a very large offset with vB. Note that this server is not a VM under pA or pB.

$ ntpq -nc peers
     remote           refid      st t when poll reach delay   offset  jitter
==============================================================================
*10.93.XXX.XXX   216.218.254.202  2 u   81  256  377 0.433  -87.076  20.341
 10.93.XXX.XXX   216.218.254.202  2 u  290  512  377 0.673  11487.6 9868.84

I.e., what happened is that the first one, using the extra parameters, kept its clock accurate while the second did not.

Sunday, 28 September 2014

Multiple relay configuration based on sender address with sendmail

One of the needs that came up was to be able to use separate relay configurations based on the sender email address, using sendmail. The problem is that sendmail is missing support for most parts of that sentence.

At the end the solution involved a combination of sendmail, smarttable, procmail and msmtp

The idea is the following:

Use smarttable to implement sender based rules

Use the procmail mailer support to use procmail to deliver the emails

Use procmailrc to pipe messages to msmtp

Use msmtp to relay via external hosts

Sender based rules

In order to be able to have sender-based rules I used smarttable.m4 from here.

Download the smarttable.m4 and (assuming sendmail config is under /etc/mail) place it under /etc/mail/m4/. Normally it should be placed along the rest of the sendmail features (/usr/share/sendmail/cf/features) but I don't like polluting system dirs. Then use the following config in sendmail.mc:

dnl Change the _CF_DIR for a bit to load the feature from /etc/mail/m4
dnl then change it back
define(`_CF_DIR_OLD', _CF_DIR_)dnl
define(`_CF_DIR_', `/etc/mail/m4/')dnl
dnl This has to be a hash. I.e. not text.
FEATURE(`smarttable',`hash -o /etc/mail/smarttable')dnl
define(`_CF_DIR_', _CF_DIR_OLD)dnl

Then configure smarttable (/etc/mail/smarttable) like this:

test@test.com    procmail:/etc/mail/persource/test.test.com.procmailrc

You can add as many lines as you like, one for each sender. See smarttable's web page for more information on the supported sender formats. Dont' forget to generate the hashed version (smarttable.db)

Procmail config

Configure sendmail for procmail mailer like this:

define(`PROCMAIL_MAILER_ARGS', `procmail -Y -t -m $h $f $u')dnl
MAILER(`procmail')dnl

You have to override the default procmail parameters in order to add the -t switch. This way delivery errors will be interpreted as softfails, otherwise mails will be rejected on the first failure.

Create /etc/mail/persource and put the procmail configs in there (nice and tidy). In this example create /etc/mail/persources/test.test.com.procmailrc as follows:

:0w
|/usr/bin/msmtp -C /etc/mail/persource/test.test.com.msmtprc -a test@test.com -t

The 'w' flag is essential in order to feed failures back to sendmail.

Msmtp config

Create the msmtp config file (/etc/mail/persource/test.test.com.msmtprc) as follows:

defaults
syslog          on
# logfile /tmp/msmtp-test@test.com.log

account         test@test.com
host            smtp.gmail.com
from            test@test.com
user            test@test.com
password        xxx
auth            on
tls             on
tls_trust_file  /etc/ssl/certs/ca-certificates.crt

Your mileage may vary. They above is good for gmail accounts on a debian system.

Done

And that's it. Sending an email as test@test.com will cause sendmail to use smarttable. This will match the sender and use procmail with our config to deliver the email. Procmail will pipe the email to msmtp which will send the email via google's email servers.

Sunday, 30 September 2012

IPsec, Racoon, setkey, Linux, Mikrotik, tunnel, transport and everything

It took me more than 6 months in order to sort all issues, so here are the experiences. Most of the trouble was because I didn't knew or I didn't had things clear in my mind.

I wanted to have IPsec communication between a bunch of servers and a home network. I believe that this includes almost all (if not all) the possible scenarios of IPsec so it's more complicated than it sounds. For obvious reasons I'm presenting a simplified version here omitting all duplicates (i.e. multiple hosts with the same characteristics).

The network

We have the following nodes:

A network behind a DSL line (home network) (normal, home DSL line with non-static IP, with NAT)

A server (srv1) somewhere on the Internet with a static public IP address without NAT.

A server (srv2) in Amazon's EC2 which has an allocated public IP address but uses local IP addresses and thus has NAT. Also Amazon doesn't allow ESP and AH protocol to be carried by IP packets inside their network.

We also have the following systems:

Home network: A bunch of Linux boxes on a private network plus a mikrotik router

srv1 and srv2: Squeeze Debian Linux

The home network uses IP addresses from the network 10.1.0.0/16. A secondary prefix (10.5.0.0/16) is allocated for IPsec addressing only. All home nodes have addresses from the 10.1.0.0/16. Some nodes (including the servers) have addresses from 10.5.0.0/16.

Apart from the above there's a custom CA setup which publishes certificates for all nodes.

The problem

Setup IPsec so that:

srv1 and srv2 can communicate with their public IP addresses with IPsec only

boxes on the home network can communicate both with srv1 and srv2 using IPsec

The setup

Since there are more than one boxes on the home network, the home network needs to be connected with tunneled IPsec to srv1 and srv2. srv1 and srv2 need to be connected with transport mode between them in order to encrypt communication that uses their public IP addresses.

We have setup the DSL router to forward everything to the mikrotik box (routerboard). This is usually referred as DMZ. By doing that it's possible to avoid NAT in IPsec (i.e. UDP encapsulation).

The solution

Mikrotik

In short, Mikrotik's IPsec works quite well and is easy to setup assuming that everything is correct. It is however harder to debug than Racoon. Here's the setup:

Add an IP address from 10.5.0.0/16

Import the box's certificate to the certificate storage, both certificate and public key are needed

Import CA's and other boxes' certificates to the certificate storage. Make sure you use sensible names to be able to look them up later.

Create a new proposal as follows:
- Name: short (or pick something else)
- Lifetime: 00:10:00 - This is essential in older to allow quick recovery when the IP address changes or racoon is restarted.
- Pick your favorite values for everything else

Add two peers, one for each server:
- srv1 (static public IP, no NAT):
  - Address: The public IP of srv1
  - Port: 500
  - Auth method: rsa signature
  - Certificate: Pick the local certificate (mikrotik's)
  - Remote certificate: Pick the certificate of srv1
  - Exchange Mode: main
  - Select: Send Initial Contact
  - Nat Traversal: No
  - My ID User FQDN: Leave empty - isn't needed
  - Proposal check: Claim (remember not to use similar or stricter on remote end)
  - Generate policy: No
  - Lifetime: 08:00:00
  - DPD Interval/Max failures: I use 10/3 but it doesn't make a difference. See notes bellow
- srv2 (static IP, public IP, with NAT): Use the same settings as with srv1
  - I didn't use NAT but it may be worth testing it.

You need to add two policies per peer. One for each local source IP address range (10.1.0.0/16 and 10.5.0.0/16). So you will end up with 4 policies:
- Src Address: 10.1.0.0/16 or 10.5.0.0/16
- Dst Address: srv1's or srv2's public IP address
- Src/Dst Port: Empty
- Protocol: all (255)
- Action: Encrypt
- Level: Unique - very important
- IPsec protocols: ESP
- Tunnel: Yes
- SA Src address: 0.0.0.0
- SA Dst address: srv1's or srv2's IPsec IP address (i.e. allocated addresses from the 10.5.0.0/16)
- Proposal: short (or whatever name you picked for the proposal you created)

Create a script named "ping-servers" (System -> Scripts) as follows:

{
 :local servers
 :local locals

 :set servers {"10.5.1.11";"10.5.1.12"}
 :set locals {"10.1.1.1";"10.5.1.1"}

 foreach loc in=$locals do={
 foreach srv in=$servers do={
 put "ping $srv src-address=$loc count=1"
 ping $srv src-address=$loc count=1
 }
 }
}

servers is the list of server's addresses from the 10.5.0.0/16 network and locals are local addresses to the mikrotik box, one for each of the two networks.

Schedule the script to be executed every minute (System -> Scheduler). This will keep the policies active and also reactivate them if they go down.

srv1 (static public IP, no NAT)

Put the following in /etc/ipsec-tools.d/srv2.conf:

spdadd srv1public srv2public[500] udp -P out none;
spdadd srv2public srv1public[500] udp -P in none;
spdadd srv1public srv2public[4500] udp -P out none;
spdadd srv2public srv1public[4500] udp -P in none;
spdadd srv1public srv2public 50 -P out none;
spdadd srv2public srv1public 50 -P in none;
spdadd srv1public srv2public 51 -P out none;
spdadd srv2public srv1public 51 -P in none;

spdadd srv1public srv2public any -P out ipsec
        esp/transport/srv1public[4500]-srv2public[4500]/require ;

spdadd srv2public srv1public any -P in ipsec
        esp/transport/srv2public[4500]-srv1public[4500]/require ;

Put the following in /etc/ipsec-tools.d/srv2-priv.conf. Somehow it is required in order to establish the IPsec connection when it's triggered by srv2:

spdadd srv1public srv2private[500] udp -P out none;
spdadd srv2private srv1public[500] udp -P in none;
spdadd srv1public srv2private[4500] udp -P out none;
spdadd srv2private srv1public[4500] udp -P in none;
spdadd srv1public srv2private 50 -P out none;
spdadd srv2private srv1public 50 -P in none;
spdadd srv1public srv2private 51 -P out none;
spdadd srv2private srv1public 51 -P in none;

spdadd srv1public srv2private any -P out ipsec
        esp/transport/srv1public[4500]-srv2private[4500]/require ;

spdadd srv2private srv1public any -P in ipsec
        esp/transport/srv2private[4500]-srv1public[4500]/require ;

In the above, srv1public is the public static IP address of srv1, srv2public is the public static IP address of srv2 and srv2private is the private static IP address of srv2.

Setup racoon.conf's section for srv2 and home as follows. Obviously you need to change to match your parameters:

remote "srv2" {
 exchange_mode main,base;
 verify_identifier on;
 peers_identifier asn1dn "Common name of srv2's certificate";
 remote_address srv2public;
 verify_cert on;
 certificate_type x509 "srv1.crt" "srv1.key";
 ca_type x509 "cacert.pem";
 my_identifier asn1dn;
 lifetime time 24 hours;
 nat_traversal on;
 proposal {
  authentication_method rsasig;
  encryption_algorithm 3des;
  hash_algorithm md5;
  dh_group modp1024;
 }
 passive off;
 proposal_check obey;
 generate_policy off;
 dpd_delay 10;
 dpd_retry 10;
 dpd_maxfail 6;
 initial_contact on;
 ike_frag on;
}

Setup racoon.conf's section for the home network as follows:

remote "home" {
 exchange_mode main,base;
 verify_identifier on;
 peers_identifier asn1dn "Common name of mikrotik's certificate ";
 verify_cert on;
 certificate_type x509 "srv1.crt" "srv1.key";
 ca_type x509 "cacert.pem";
 my_identifier asn1dn;
 nat_traversal off;
 proposal {
  authentication_method rsasig;
  encryption_algorithm 3des;
  hash_algorithm md5;
  dh_group modp1024;Â Â Â Â Â  # Group 2
 }
 passive on;
 proposal_check obey;
 generate_policy unique;
 dpd_delay 10;
 dpd_retry 10;
 dpd_maxfail 6;
 initial_contact on;
 ike_frag on;
}

Notice the differences: passive should be onÂ for the home network since it's not possible to trigger that without remote address.

Notice the generate_policy. It must be "unique" and not "on". Otherwise only one policy per remote endpoint will be generated and will also cause problems when an SA becomes bad.

Setup the additional address to a loopback interface and not to a physical interface.

Add static routes for the two networks using the normal gateway and specifying the source IP address. Otherwise you will be using the tunnel with addresses that are not routed via the tunnel and are not protected by IPsec. Obviously this will prevent anything from working on top of IPsec. Surprisingly, this will work occasionally when the traffic is initiated by the remote end just because of the route cache. Your config can be added to the loopback interface as follows:
```
auto lo:1
iface lo:1 inet static
  addressÂ Â  Â  10.5.1.12
  netmaskÂ Â  Â  255.255.255.255
  up          ip route add 10.5.0.0/16 via <gw> src 10.5.1.12 || true
  up          ip route add 10.1.0.0/16 via <gw> src 10.5.1.12 || true
  down        ip route del 10.1.0.0/16 via <gw> src 10.5.1.12 || true
  down        ip route del 10.5.0.0/16 via <gw> src 10.5.1.12 || true
```
where 10.5.1.12 is the address from the 10.5.0.0/16 network for srv1 and gw is the normal gateway of the server.

srv2 (static private IP, static public IP, NAT)

Setup the /etc/ipsec-tools.d/*.conf files in a similar way to the srv1's. You will need an entry for both the private and the public address.

Setup racoon like srv1's except from nat. You will have to set nat_traversal to on for srv1 and the home network.

The Hints / Lessons learned

Either test DPD (Dead Peer Detection) or don't use it at all. It didn't work for me at all.

You need to activate the policies from the home network's side proactively for both the IPsec networks (10.1.0.0/16 and 10.5.0.0/16). Otherwise it will be impossible for the remote ends to connect to local hosts. This is easily done by setting up a ping to run every minute. You need one ping per source IP address using -I.

You need to exclude ISAKMP traffic (UDP ports 500 and 4500) from static IPsec policies or otherwise you will have problems since outgoing traffic will be encrypted and incoming traffic will be dropped if not encrypted, which causes huge issues when one end goes down and requires the IPsec SA to expire from both ends (or flushed) before working again.

If you have firewall rules make sure that you allow ISAKMP traffic and IPsec traffic (protocols 50 (esp) and 51 (ah))

If you get errors that say that a policy is not available then it is not available! I can't stress this enough. While trying to make IPsec to work your brain will enter a bad state and it will start making mistakes. It's extremely easy to confuse static IPsec rules. I've done all sorts of mistakes including (but not limited to): using the wrong direction (in/out), using the address of another server, using tunnel instead of transport (and vice versa), not including the port numbers for esp-udp (UDP encapsulation) mode, not using the .conf extensions for files under /etc/ipsec-tools.d/, etc. Here's an example of that:
```
Sep 27 15:02:04 srvX racoon: ERROR: no policy found: A.B.C.D/32[0] E.F.G.H/32[0] proto=any dir=in
Sep 27 15:02:04 srvX racoon: ERROR: failed to get proposal for responder.
Sep 27 15:02:04 srvX racoon: [I.J.K.L] ERROR: failed to pre-process ph2 packet (side: 1, status: 1).
```

When testing a connection from host A that has both the 10.1.1.1 and 10.5.1.1 addresses to host B with address 10.5.1.2 then you may not be able to ping from B to one of the A's addresses. That's because only one of the IPsec policies is activated. To activate both of them use -I parameter for ping:
```
v13@hostA$ ping -I 10.1.1.1 10.5.1.2
v13@hostA$ ping -I 10.5.1.1 10.5.1.2
```

Pay attention to routing. You need to use the proper source IP addresses.

Tuesday, 24 July 2012

rsync as root with rrsync and sudo

Here's how to rsync something to a remote host as root without allowing root logins and with directory restriction. I did that because I wanted to sync /srv across servers.

In general it will use rsync over ssh, sudo, rrsync and a remote non-root user. I assume that rsync will run from srv1 to srv2.

rrsync

First you will need the rrsync (or rrsync.pl) script ad the server side that's part of the rsync package. In Debian you can find it at /usr/share/doc/rsync/scripts/rrsync.gz. This script acts as the server side and will restrict the destination directory (a'la chroot).

In short the server side will run "rrsync /srv". Then the client side will do something like this:

[code light="true"]
# rsync /srv remote:/
[/code]

and / will be relative to /srv that was defined as a parameter to rrsync.

You can put rrsync under /usr/local/bin.

User on srv2

At the destination server we will need a user that will be used for the ssh session. So go and create a user named 'syncer' on srv2. I'd avoid a username of 'rsync' as it may be used for other reasons at some point.

sudo on srv2

The user on srv2 should be able to run rrsync with sudo and with the -E parameter. -E is required in order to pass the checks of the rrsync script which checks for SSH_ORIGINAL_COMMAND in the environment. Feel free to make this even more strict to allow only this environment variable if you like.

Sample sudoers entry (e.g. to be put in /etc/sudoers.d/syncer):

[code light="true"]
syncerÂ Â Â ALL=SETENV:NOPASSWD:/usr/local/bin/rrsync /srv
[/code]

Obviously we need the user to be able to run this without requiring a password. SETENV will allow for the -E parameter to sudo.

SSH config

Next step is to allow root@srv1 to ssh as syncer@srv2 using public key. If you don't have a key pair generated for root@srv1 then go ahead and create it:

[code light="true"]
# ssh-keygen
[/code]

Then copy the contents of /root/.ssh/id_rsa.pub and paste them in syncer@srv2's authorized_keys file which is most probably at /home/srv2/syncer/.ssh/authorized_keys. Create the directory and the file if they don't exist.

To make rrsync work and make things safer you need to use the command=".." parameter and you should use the from=".." parameter. So your authorized_keys file will look something like this:

[code light="true" wraplines="true"]
from="srv1",command="sudo -E /usr/local/bin/rrsync /srv" ssh-rsa AAAA......siW root@srv1
[/code]

Don't forget to ssh at least once from srv1 to srv2 by hand in order to accept srv2's key and let ssh have it in in known_hosts.

Try it

Finally you are done and you can do the rsync:

[code light="true"]
# rsync --rsh=ssh -a --delete /srv syncer@srv2:/
[/code]

Sunday, 25 March 2012

Linux Containers: Easy LXC

Linux containers (a.k.a. LXC) rock. It's the ultimate way of having multiple Linux boxes with minimal requirements.

Here's how I do it under Debian (and the script I'm using):

Requirements

This guide is for DebianÂ testing as of 25 March 2012. However it should work for other cases as well.

The procedure creates a minimal installation which can then be fully customized by hand or with puppet. The procedure installs Debian under Debian but should be easy to change for other distributions as well (especially Ubuntu).

Packages

You will need to install:

lxc - The linux containers package

bridge-utils - For bridging network interfaces

uml-utilities - For tun/tap interfaces

cdebootstrap - For the bootstrapping of the virtual machines

puppet (optional) - for managing multiple machines

Networking

I prefer networking between lxc installations to be separate from my normal network. It is trivial however to bridge with the outside network as well.

Add the following to /etc/network/interfaces:

[code]
auto virtlxc
iface virtlxc inet manual
tunctl_userÂ Â Â Â root
upÂ Â Â Â Â Â Â Â Â Â Â Â Â ip link set virtlxc up
downÂ Â Â Â Â Â Â Â Â Â Â ip link set virtlxc down

auto brvirt
iface brvirt inet static
bridge_portsÂ Â Â Â Â Â Â Â Â Â Â virtlxc
bridge_maxwaitÂ Â Â Â Â Â Â Â Â 0
bridge_stpÂ Â Â Â Â Â Â Â Â Â Â Â Â off
addressÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 10.3.1.1
netmaskÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 255.255.255.0
dns-searchÂ Â Â Â Â Â Â Â Â Â Â Â Â virt.local
[/code]

Then add the following to /etc/hosts:

[code]
10.3.1.1Â Â Â deb0 deb0.virt deb0.virt.local
10.3.1.11Â Â Â deb1 deb1.virt deb1.virt.local
10.3.1.12Â Â Â deb2 deb2.virt deb2.virt.local
10.3.1.13Â Â Â deb3 deb3.virt deb3.virt.local
10.3.1.14Â Â Â deb4 deb4.virt deb4.virt.local
[/code]

Add as many entries as you like. There should be one entry per virtual machine. It doesn't matter if you have more entries than virtual machines since you may use them in the future. The first (deb) entry is for the local machine.

Bring up the brvirt and virtlxc interfaces and keep reading (ifup virtlxc; ifup brvirt).

You may also want to run something like this to provide network access to the virtual machines (assuming that eth0 is the interface the connects you to the rest of the world):

[code]
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -I POSTROUTING -o eth0 -s 10.3.1.0/24 -j MASQUERADE
[/code]

Create the virtual machine

Get the following script and change the desired variables at the beginning as follows (assuming that you followed the network configuration):

SUITE: The Debian suite to use (e.g. squeeze)

MIRROR: A mirror to download debian from. If you use approx like me then you want to use the local machine (i.e. 10.3.1.1)

VIRTUSER: A username you want to have created in the virtual machine. After that you may ssh as that user.

LOCALUSERS: A space separated list of local users to get ssh public keys from and put then in VIRTUSER's authorized_keys file to allow ssh.

PUPPETMASTER: Leave it empty if you don't have a puppet master.

DNSSERVER: The DNS server to use. By default it is the local machine.

Each virtual machine should get a unique MAC address. The MAC addresses are auto-generated from the current y/m/d/H/M, so you should not create more than one virtual machines every minute. You're free to change this of course.

Now run the script at the end of the page and let it create a virtual machine:

[code]
./easylxc deb1
[/code]

The installation will happen under /var/lib/lxc (the default for lxc). You may visit that and fix things by hand if you (i.e.) manage to lock yourself out.

The virtual machine can be started with:

[code]
lxc-start -n deb4
- or -
lxc-start -n deb4 -d
[/code]

However, a bug/feature of rxvt will prevent that for succeeding. In that case you can run:

[code]
sudo lxc-start -n deb4
- or -
sudo lxc-start -n deb4 -d
[/code]

Inside the virtual machine you will be able to su to root by using "su" without password. You will be also able to ssh as root (using the same ssh keys).

Hints'n'tips

I strongly suggest using approx and changing the MIRROR variable as needed. It will speed the creation of many machines by orders of magnitude since there will be no network delays.

The script

[code lang="bash"]
#!/bin/bash

if [ -z "$1" ] ; then
echo "Pass the name of the machine as the first parameter"
exit 1
fi

# The name of the container to create. Also used as the hostname
NAME="$1"

# The name of the parent (local) machine without the domain
PARENTNAME="deb0"

# Distribution
SUITE="squeeze"

# The domain to be used by the virtual machines.
DOMAIN="virt.hell.gr"

# The network prefix (first 3 octets - it is assumed to be a /24 network)
NETPREFIX="10.3.1"

# Since we use approx, this is the approx server. If not, add a mirror.
MIRROR="http://ftp.debian.org/debian/"

# The gateway address for the virtual machine. This is most probably the
# address of the bridge interface.
GW="$NETPREFIX.1"

# The bridge interface to use for networking
BRIDGEIF="brvirt"

# The username of the user to create inside the container
VIRTUSER="v13"

# A list of local users that will have ssh access to the container
# They need to have a public key in the local machine
LOCALUSERS="v13 root"

# The puppet master. This must be the hostname of the master (not an IP addr).
# No puppet if this is empty.
PUPPETMASTER=""

# The DNS server to use.
DNSSERVER="$GW"

IPADDR2=$(getent hosts $NAME.$DOMAIN | awk '{print $1}')

if [ "x$IPADDR2" = "x169.254.1.1" ] ; then
IPADDR2=""
fi

if [ -z "$IPADDR2" ] ; then
echo "Could not resolve $NAME.$DOMAIN"
exit 1
fi

IPADDR="$IPADDR2/24"

MAC=$(date "+4a:%y:%m:%d:%H:%M")

lxc-stop -n $NAME
lxc-destroy -n $NAME

export SUITE
export MIRROR

R0=/var/lib/lxc/$NAME
R=$R0/rootfs

mkdir $R0 $R

# Install base system
echo cdebootstrap -f standard $SUITE $R $MIRROR
cdebootstrap -f standard $SUITE $R $MIRROR

CFG=$R0/config

# Create config file
cat << _KOKO > $CFG
# Auto-generated by: $*
# at $(date)

## Container
lxc.utsname = $NAME
lxc.rootfs = $R
lxc.tty = 6
lxc.pts = 1024

## Network
lxc.network.type = veth
lxc.network.hwaddr = $MAC
lxc.network.link = $BRIDGEIF
lxc.network.veth.pair = veth-$NAME

## Capabilities
lxc.cap.drop = mac_admin
lxc.cap.drop = mac_override
lxc.cap.drop = sys_admin
lxc.cap.drop = sys_module

## Devices
# Allow all device
lxc.cgroup.devices.allow = a
# Deny all device
lxc.cgroup.devices.deny = a
# Allow to mknod all devices (but not using them)
lxc.cgroup.devices.allow = c *:* m
lxc.cgroup.devices.allow = b *:* m

# /dev/console
lxc.cgroup.devices.allow = c 5:1 rwm
# /dev/fuse
lxc.cgroup.devices.allow = c 10:229 rwm
# /dev/null
lxc.cgroup.devices.allow = c 1:3 rwm
# /dev/ptmx
lxc.cgroup.devices.allow = c 5:2 rwm
# /dev/pts/*
lxc.cgroup.devices.allow = c 136:* rwm
# /dev/random
lxc.cgroup.devices.allow = c 1:8 rwm
# /dev/rtc
lxc.cgroup.devices.allow = c 254:0 rwm
# /dev/tty
lxc.cgroup.devices.allow = c 5:0 rwm
# /dev/urandom
lxc.cgroup.devices.allow = c 1:9 rwm
# /dev/zero
lxc.cgroup.devices.allow = c 1:5 rwm
# /dev/net/tun
lxc.cgroup.devices.allow = c 10:200 rwm

## Limits
#lxc.cgroup.cpu.shares = 1024
#lxc.cgroup.cpuset.cpus = 0
#lxc.cgroup.memory.limit_in_bytes = 256M
#lxc.cgroup.memory.memsw.limit_in_bytes = 1G

## Filesystem
lxc.mount.entry = proc $R/proc proc nodev,noexec,nosuid 0 0
lxc.mount.entry = sysfs $R/sys sysfs defaults,ro 0 0

_KOKO

# fix interfaces
T=$R/etc/network/interfaces
mv $T $T.orig
(
cat $T.orig \
| sed "s/^iface eth0.*$//"
echo "
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address $IPADDR2
netmask 255.255.255.0
gateway $GW
dns-nameservers $DNSSERVER
"
) > $T
rm $T.orig

# fix resolv.conf
T=$R/etc/resolv.conf
cat << _KOKO > $T
domain $DOMAIN
search $DOMAIN
nameserver $GW
_KOKO

# add info to hosts
T=$R/etc/hosts
echo "$IPADDR2 $NAME $NAME.$DOMAIN" >> $T
echo "$GW gw gw.$DOMAIN $PARENTNAME.$DOMAIN $PARENTNAME" >> $T

# set debian_chroot (for help)
echo "lxc-$NAME" >> $R/etc/debian_chroot

# create ttys
for i in $(seq 0 6) ; do
mknod $R/dev/tty$i c 4 $i
done

run()
{
echo chroot $R "$@"
LC_ALL=C chroot $R "$@"
}

run2()
{
ssh -o StrictHostKeyChecking=no $IPADDR2 "$@"
}

runmaster()
{
ssh -o StrictHostKeyChecking=no $PUPPETMASTER "$@"
}

# Install locales
run apt-get -y install locales

# disable init scripts
DISABLED="bootlogd bootlogs checkfs.sh checkroot.sh halt hostname.sh \
hwclockfirst.sh hwclock.sh module-init-tools mountall.sh \
mountdevsubfs.sh mountkernfs.sh mountnfs.sh mountoverflowtmp procps \
reboot stop-bootlogd stop-bootlogd-single udev umountfs umountnfs.sh \
umountroot"
for dis in $DISABLED ; do
run update-rc.d $dis disable
done

# disable rsyslog's kernel logging
run sed -i 's/^$.*imklog.*$$/#\1/' /etc/rsyslog.conf

# add user
run adduser --gecos $VIRTUSER --disabled-password $VIRTUSER
run adduser $VIRTUSER root

# fix sources.list
T=$R/etc/apt/sources.list
cat << _KOKO > $T
deb $MIRROR $SUITE main
_KOKO

# Install ssh
run apt-get update
run apt-get -y install openssh-server
run /etc/init.d/ssh stop

# Fix root and su
run passwd -l root
T=$R/etc/pam.d/su
mv $T $T.old
cat $T.old \
| sed 's/^# $.*pam_wheel.so trust$/\1/' \
> $T
rm $T.old

# Add ssh keys
T=$R/home/$VIRTUSER/.ssh/authorized_keys
T2=$R/root/.ssh/authorized_keys
mkdir $R/home/$VIRTUSER/.ssh $R/root/.ssh
for u in $LOCALUSERS ; do
H=$(getent passwd $u | cut -f 6 -d : )
cat $H/.ssh/id_rsa.pub >> $T
cat $H/.ssh/id_rsa.pub >> $T2
done
chown $VIRTUSER.$VIRTUSER $R/home/$VIRTUSER/.ssh $T
chown root.root $R/home/$VIRTUSER/.ssh $T2

# Start it
# Use sudo to bypass file descriptor problems
sudo lxc-start -n $NAME -d
sleep 1

if ! [ -z "$PUPPETMASTER" ] ; then
# Install packages
run2 apt-get -y install puppet

# Clear any existing certificate
runmaster puppet cert clean $NAME.$DOMAIN

# Fix puppet config
T=$R/etc/default/puppet
mv $T $T.old
cat $T.old \
| sed 's/START=no/START=yes/' \
| sed "s/DAEMON_OPTS=\"\"/DAEMON_OPTS=\"--server=$PUPPETMASTER --verbose\"/" \
> $T
rm -rf $T.old

run2 puppet agent --server=$PUPPETMASTER --no-daemonize --onetime

# sign the certificate
runmaster puppet cert --sign $NAME.$DOMAIN

run2 /etc/init.d/puppet start
fi

cat << _KOKO

LXC virtual box is ready!

Config file is at: $R0/config
Root fs is at: $R

Get a console with:
lxc-console -n $NAME

Stop it with:
lxc-stop -n $NAME

Start it with:
lxc-start -n $NAME -d

_KOKO
[/code]
Update: You can use the above code under the GPLv3 license.

#!/bin/bash

if [ -z "$1" ] ; then
echo "Pass the name of the machine as the first parameter"
exit 1
fi

# The name of the container to create. Also used as the hostname
NAME="$1"

# The name of the parent (local) machine without the domain
PARENTNAME="deb0"

# Distribution
SUITE="squeeze"

# The domain to be used by the virtual machines.
DOMAIN="virt.hell.gr"

# The network prefix (first 3 octets - it is assumed to be a /24 network)
NETPREFIX="10.3.1"

# Since we use approx, this is the approx server. If not, add a mirror.
MIRROR="http://ftp.debian.org/debian/"

# The gateway address for the virtual machine. This is most probably the
# address of the bridge interface.
GW="$NETPREFIX.1"

# The bridge interface to use for networking
BRIDGEIF="brvirt"

# The username of the user to create inside the container
VIRTUSER="v13"

# A list of local users that will have ssh access to the container
# They need to have a public key in the local machine
LOCALUSERS="v13 root"

# The puppet master. This must be the hostname of the master (not an IP addr).
# No puppet if this is empty.
PUPPETMASTER=""

IPADDR2=$(getent hosts $NAME.$DOMAIN | awk '{print $1}')

if [ "x$IPADDR2" = "x169.254.1.1" ] ; then
IPADDR2=""
fi

if [ -z "$IPADDR2" ] ; then
echo "Could not resolve $NAME.$DOMAIN"
exit 1
fi

IPADDR="$IPADDR2/24"

MAC=$(date "+4a:%y:%m:%d:%H:%M")

lxc-stop -n $NAME
lxc-destroy -n $NAME

export SUITE
export MIRROR

R0=/var/lib/lxc/$NAME
R=$R0/rootfs

mkdir $R0 $R

# Install base system
echo cdebootstrap -f standard $SUITE $R $MIRROR
cdebootstrap -f standard $SUITE $R $MIRROR

CFG=$R0/config

# Create config file
cat << _KOKO > $CFG
# Auto-generated by: $*
# at $(date)

## Container
lxc.utsnameÂ Â Â Â Â Â = $NAME
lxc.rootfsÂ Â Â Â Â Â = $R
lxc.ttyÂ Â Â Â Â Â Â Â Â = 6
lxc.ptsÂ Â Â Â Â Â Â Â Â = 1024

## Network
lxc.network.typeÂ Â Â = veth
lxc.network.hwaddrÂ Â Â = $MAC
lxc.network.linkÂ Â Â = $BRIDGEIF
lxc.network.veth.pairÂ Â Â = veth-$NAME

## Capabilities
lxc.cap.dropÂ Â Â Â Â Â = mac_admin
lxc.cap.dropÂ Â Â Â Â Â = mac_override
lxc.cap.dropÂ Â Â Â Â Â = sys_admin
lxc.cap.dropÂ Â Â Â Â Â = sys_module

## Devices
# Allow all device
lxc.cgroup.devices.allowÂ Â Â = a
# Deny all device
lxc.cgroup.devices.denyÂ Â Â Â Â Â = a
# Allow to mknod all devices (but not using them)
lxc.cgroup.devices.allowÂ Â Â = c *:* m
lxc.cgroup.devices.allowÂ Â Â = b *:* m

# /dev/console
lxc.cgroup.devices.allowÂ Â Â = c 5:1 rwm
# /dev/fuse
lxc.cgroup.devices.allowÂ Â Â = c 10:229 rwm
# /dev/null
lxc.cgroup.devices.allowÂ Â Â = c 1:3 rwm
# /dev/ptmx
lxc.cgroup.devices.allowÂ Â Â = c 5:2 rwm
# /dev/pts/*
lxc.cgroup.devices.allowÂ Â Â = c 136:* rwm
# /dev/random
lxc.cgroup.devices.allowÂ Â Â = c 1:8 rwm
# /dev/rtc
lxc.cgroup.devices.allowÂ Â Â = c 254:0 rwm
# /dev/tty
lxc.cgroup.devices.allowÂ Â Â = c 5:0 rwm
# /dev/urandom
lxc.cgroup.devices.allowÂ Â Â = c 1:9 rwm
# /dev/zero
lxc.cgroup.devices.allowÂ Â Â = c 1:5 rwm
# /dev/net/tun
lxc.cgroup.devices.allowÂ Â Â Â Â Â Â = c 10:200 rwm

## Limits
#lxc.cgroup.cpu.sharesÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 1024
#lxc.cgroup.cpuset.cpusÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 0
#lxc.cgroup.memory.limit_in_bytesÂ Â Â Â Â Â = 256M
#lxc.cgroup.memory.memsw.limit_in_bytes = 1G

## Filesystem
lxc.mount.entryÂ Â Â Â Â Â = proc $R/proc proc nodev,noexec,nosuid 0 0
lxc.mount.entryÂ Â Â Â Â Â = sysfs $R/sys sysfs defaults,ro 0 0

_KOKO

# fix interfaces
T=$R/etc/network/interfaces
mv $T $T.orig
(
cat $T.orig \
| sed "s/^iface eth0.*$//"
echo "
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
addressÂ Â Â Â Â Â Â Â Â $IPADDR2
netmaskÂ Â Â Â Â Â Â Â Â 255.255.255.0
gatewayÂ Â Â Â Â Â Â Â Â $GW
dns-nameserversÂ Â Â Â Â Â $GW
"
) > $T
rm $T.orig

# fix resolv.conf
T=$R/etc/resolv.conf
cat << _KOKO > $T
domain $DOMAIN
search $DOMAIN
nameserver $GW
_KOKO

# add info to hosts
T=$R/etc/hosts
echo "$IPADDR2 $NAME $NAME.$DOMAIN" >> $T
echo "$GW gw gw.$DOMAIN $PARENTNAME.$DOMAIN $PARENTNAME" >> $T

# set debian_chroot (for help)
echo "lxc-$NAME" >> $R/etc/debian_chroot

# create ttys
for i in $(seq 0 6) ; do
mknod $R/dev/tty$i c 4 $i
done

run()
{
echo chroot $R "$@"
LC_ALL=C chroot $R "$@"
}

run2()
{
ssh -o StrictHostKeyChecking=no $IPADDR2 "$@"
}

runmaster()
{
ssh -o StrictHostKeyChecking=no $PUPPETMASTER "$@"
}

# Install locales
run apt-get -y install locales

# disable init scripts
DISABLED="bootlogd bootlogs checkfs.sh checkroot.sh halt hostname.sh \
hwclockfirst.sh hwclock.sh module-init-tools mountall.sh \
mountdevsubfs.sh mountkernfs.sh mountnfs.sh mountoverflowtmp procps \
reboot stop-bootlogd stop-bootlogd-single udev umountfs umountnfs.sh \
umountroot"
for dis in $DISABLED ; do
run update-rc.d $dis disable
done

# disable rsyslog's kernel logging
run sed -i 's/^$.*imklog.*$$/#\1/' /etc/rsyslog.conf

# add user
run adduser --gecos $VIRTUSER --disabled-password $VIRTUSER
run adduser $VIRTUSER root

# fix sources.list
T=$R/etc/apt/sources.list
cat << _KOKO > $T
deb $MIRROR $SUITE main
_KOKO

# Install ssh
run apt-get update
run apt-get -y install openssh-server
run /etc/init.d/ssh stop

# Fix root and su
run passwd -l root
T=$R/etc/pam.d/su
mv $T $T.old
cat $T.old \
| sed 's/^# $.*pam_wheel.so trust$/\1/' \
> $T
rm $T.old

# Add ssh keys
T=$R/home/$VIRTUSER/.ssh/authorized_keys
T2=$R/root/.ssh/authorized_keys
mkdir $R/home/$VIRTUSER/.ssh $R/root/.ssh
for u in $LOCALUSERS ; do
H=$(getent passwd $u | cut -f 6 -d :)
cat $H/.ssh/id_rsa.pub >> $T
cat $H/.ssh/id_rsa.pub >> $T2
done
chown $VIRTUSER.$VIRTUSER $R/home/$VIRTUSER/.ssh $T
chown root.root $R/home/$VIRTUSER/.ssh $T2

# Start it
# Use sudo to bypass file descriptor problems
sudo lxc-start -n $NAME -d
sleep 1

if ! [ -z "$PUPPETMASTER" ] ; then
# Install packages
run2 apt-get -y install puppet

# Clear any existing certificate
runmaster puppet cert clean $NAME.$DOMAIN

# Fix puppet config
T=$R/etc/default/puppet
mv $T $T.old
cat $T.old \
| sed 's/START=no/START=yes/' \
| sed "s/DAEMON_OPTS=\"\"/DAEMON_OPTS=\"--server=$PUPPETMASTER --verbose\"/" \
> $T
rm -rf $T.old

run2 puppet agent --server=$PUPPETMASTER --no-daemonize --onetime

# sign the certificate
runmaster puppet cert --sign $NAME.$DOMAIN

run2 /etc/init.d/puppet start
fi

cat << _KOKO

LXC virtual box is ready!

Config file is at: $R0/config
Root fs is at: $R

Get a console with:
lxc-console -n $NAME

Stop it with:
lxc-stop -n $NAME

Start it with:
lxc-start -n $NAME -d

_KOKO

Monday, 2 January 2012

Big nfs_inode_cache

The story

Boxes with various kernel versions have weird free memory problems. After examining the memory usage it seems that processes don't add up to the actual memory that is being used.

Taking a look at /proc/meminfo we see something like this:

[code]
MemTotal:Â Â Â Â Â 8161544 kB
MemFree:Â Â Â Â Â Â Â 115676 kB
Buffers:Â Â Â Â Â Â Â Â Â 3900 kB
Cached:Â Â Â Â Â Â Â Â 200520 kB
SwapCached:Â Â Â Â Â 42336 kB
Active:Â Â Â Â Â Â Â Â 546824 kB
Inactive:Â Â Â Â Â Â 138336 kB
HighTotal:Â Â Â Â Â Â Â Â Â Â 0 kB
HighFree:Â Â Â Â Â Â Â Â Â Â Â 0 kB
LowTotal:Â Â Â Â Â 8161544 kB
LowFree:Â Â Â Â Â Â Â 115676 kB
SwapTotal:Â Â Â Â 2096472 kB
SwapFree:Â Â Â Â Â Â 547480 kB
Dirty:Â Â Â Â Â Â Â Â Â Â Â 1020 kB
Writeback:Â Â Â Â Â Â Â Â Â Â 0 kB
AnonPages:Â Â Â Â Â 453480 kB
Mapped:Â Â Â Â Â Â Â Â Â 66928 kB
Slab:Â Â Â Â Â Â Â Â Â 7250176 kB
PageTables:Â Â Â Â Â 75408 kB
...
[/code]

Notice that Slab is about 7.5GB, almost the whole memory (8GB) (!).

Slab is the kernel memory and we can see where it is allocated by examining /proc/slabinfo. Here's an excerpt:

[code]
# nameÂ Â Â Â Â Â Â Â Â Â Â <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> : tunables <limit> <batchcount> <sharedfactor> : slabdata <active_slabs> <num_slabs> <sharedavail>
nfs_direct_cacheÂ Â Â Â Â Â 0Â Â Â Â Â 0Â Â Â 136Â Â 28Â Â Â 1 : tunablesÂ 120Â Â 60Â Â Â 8 : slabdataÂ Â Â Â Â 0Â Â Â Â Â 0Â Â Â Â Â 0
nfs_write_dataÂ Â Â Â Â Â Â 62Â Â Â Â 63Â Â Â 832Â Â Â 9Â Â Â 2 : tunablesÂ Â 54Â Â 27Â Â Â 8 : slabdataÂ Â Â Â Â 7Â Â Â Â Â 7Â Â Â Â Â 0
nfs_read_dataÂ Â Â Â Â Â Â 215Â Â Â 297Â Â Â 832Â Â Â 9Â Â Â 2 : tunablesÂ Â 54Â Â 27Â Â Â 8 : slabdataÂ Â Â Â 33Â Â Â Â 33Â Â Â Â 54
nfs_inode_cacheÂ Â 5384386 5399040Â Â 1032Â Â Â 3Â Â Â 1 : tunablesÂ Â 24Â Â 12Â Â Â 8 : slabdata 1799680 1799680Â Â Â Â 40
nfs_pageÂ Â Â Â Â Â Â Â Â Â Â Â 534Â Â Â 750Â Â Â 128Â Â 30Â Â Â 1 : tunablesÂ 120Â Â 60Â Â Â 8 : slabdataÂ Â Â Â 25Â Â Â Â 25Â Â Â 264
rpc_buffersÂ Â Â Â Â Â Â Â Â Â Â 8Â Â Â Â Â 8Â Â 2048Â Â Â 2Â Â Â 1 : tunablesÂ Â 24Â Â 12Â Â Â 8 : slabdataÂ Â Â Â Â 4Â Â Â Â Â 4Â Â Â Â Â 0
...
[/code]

Notice the nfs_inode_cache which is 5.3M objects of 1032 bytes each, adding up to about 5.4GB.

The workaround

Looking a bit about this on the internet we see that this is most probably a bug. Fortunately there are two workaround: A slow and a fast one:

Slow workaround: Login to that box and run "sync". Then leave it alone for a couple of minutes while the nfs_inode_cache memory goes down and down. It make take a couple of minutes before starting going down and there may be pauses in the process. It can take more than an hour to free the memory.

Fast workaround: Login to that box and run:

[code]
# sync
# echo 2 > /proc/sys/vm/drop_caches
[/code]

I'm not sure why the first one works, but it looks like it is triggering a chain reaction that frees the memory.

Friday, 18 February 2011

pyzor problem after debian squeeze upgrade

After upgrading some servers to Debian squeeze, the following log was filling the logs:
[code]
Feb 18 12:49:38 aetos check[982]: pyzor: [19952] error: TERMINATED, signal 15 (000f)
[/code]

The problem was caused by wrong pyzor servers. Unfortunately, pyzor keeps a servers list in each home directory in file ~/.pyzor/servers. This is what this file used to have:
[code]
82.94.255.100:24441
[/code]

This file is created automatically (with a proper value) so it is safe to remove it. That's what it should have (for now):
[code]
public.pyzor.org:24441
[/code]

In order to get rid of the error message all users' files should be deleted:
[code]
find /home -name servers | grep pyzor/servers > /tmp/lst
# examine /tmp/lst by hand to verify that nothing bad is there
cd /home
cat /tmp/lst | xargs rm
[/code]

That's it. There should be no more "TERMINATED" messages.