Alan Wylie's Web Site

Mon, 2018-09-03

About me: permalink
I'm a computer hacker (in the original meaning of the word), a caver, a fell-walker, and cyclist.

mail me at alan@wylie.me.uk

My PGP public key(s)

Note that sending unsolicited marketing e-mail to an individual in the UK is an offence under the Privacy and Electronic Communications (EC Directive) Regulations 2003 and that the collection and processing of personal information is regulated by the Data Protection Act.

alan

Fri, 2018-04-27

I started seeing repeated delivery failure messages from the Linux Kernel Mailing list: permalink

postfix/cleanup[20414]: 2819B22313: info: header Subject: Do You Need A Hand? from vger.kernel.org[209.132.180.67];
opendkim[7694]: too much header data

A quick Google suggested that this was because the header size was greater than the default of 65536 that OpenDKIM accepts. I tried increasing this to 262144, but this didn't help. I then set

On-Security            accept

in opendkim.conf. This caused the mail to be accepted. I then had a look inside the mail:

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sego.es; s=default;
<snip>

$ grep DKIM-Signature msg.5SAz | wc -l
1000

$ sed -n '1,/^$/p' msg.6SAz | wc -c
396117

What on earth are sego.es playing at?

Sun, 2018-03-11

If postfix isn't delivering mail and you have this message in your log file permalink

amavis: (!!)TROUBLE in pre_loop_hook: config: no rules were found!  Do you need to run 'sa-update'?

check the permissions on subdirectories under

/var/lib/spamassassin

e.g.

/var/lib/spamassassin/3.004001/

If root has a restrictive umask of 0077, then files need to be set world readable

chmod -R a+rX  /var/lib/spamassassin/3.004001/

Thu, 2018-03-01

"Opening '/proc/net/rpc/nfs4.nametoid/channel' failed: errno 2" permalink

If you get the above error, make sure that you have CONFIG_NFSD_V4 enabled in your kernel config.

Tue, 2018-02-27

How to load the co-ordinates of caves into OsmAnd permalink
OsmAnd is a free map app for Android.

To overlay the co-ordinates of caves:

* Use the Chrome browser
* visit http://www1.maths.leeds.ac.uk/~read/scuba/gps.html
* scroll down, then long click on a link to a GPX file.
* save to the Downloads directory

* In OsmAnd, tap on the three bars at the bottom left to open the menu
* "My places", "My Tracks", "Import"
* Tap on the icon for a file, it changes to a tick, then "Open"
* for subsequent imports, click on the "+" at the bottom left.

* Finally, on the "My tracks" page, tap on the three dots to the right of a file and "show on map".

Thu, 2018-01-11

After seeing Greg K-H's comments permalink
about old Long Term Support kernels, I updated a couple of servers from 4.4 to 4.14. I ran into a problem with named (BIND) failing to start.

kernel: mmap: named (6332): VmData 35500032 exceed data ulimit 2097152. Update limits or use boot option ignore_rlimit_data.

It seems that having the line

datasize 2M;

in named.conf is the cause. Just remove that line. It seems that it's commonly been copied for donkeys' years: I can first find it in a config from September 2003.

Thu, 2017-11-09

With systemd 235, playing "Black Mesa" in a systemd-nspawn container stopper working: permalink
Running glxinfo gave the error

libGL error: failed to open drm device: Operation not permitted

and strace showed:

open("/dev/dri/card0", O_RDWR|O_LARGEFILE|O_CLOEXEC) = -1 EPERM (Operation not permitted)

The fix is to add

--property='DeviceAllow=/dev/dri/card0 rw'

to the systemd-nspawn command line

Wed, 2017-10-04

Solved: pcap errors permalink

# iftop -i eth0
interface: eth0
pcap_open_live(eth0): eth0: socket: Address family not supported by protocol
# dmesg | tail
[595841.213279] iftop uses obsolete (PF_INET,SOCK_PACKET)

Make sure that CONFIG_PACKET and CONFIG_PACKET_DIAG are enabled in your kernel config

$ diff .config.old .config
3c3
< # Linux/x86 4.4.70 Kernel Configuration
---
> # Linux/x86 4.4.89 Kernel Configuration
635c635,636
< # CONFIG_PACKET is not set
---
> CONFIG_PACKET=m
> CONFIG_PACKET_DIAG=m
$

Tue, 2016-11-01

umount: /mnt/tmp: device is busy permalink

If you are trying to unmount a device, you get the error "device is busy", but lsof/fuser don't show any process holding the device open, it could be that a file on the device is associated with a loop device.

try

# losetup -a
/dev/loop/0: [0821]:25280514 (image) offset=55273881600
# losetup  -d /dev/loop0 
# umount /mnt/tmp

(updated, 2016-11-01)

dmsetup info | grep loop
dmsetup remove loop0p2
dmsetup remove loop0p3

may help too

Thu, 2016-03-03

More hints on unmounting a filesystem: permalink
(previously)

# ls -l /dev/mapper/
# dmsetup ls
# dmsetup info loop0p2
# dmsetup remove loop0p2
# losetup -a
# losetup -d loop0
# umount /mnt/tmp

Thu, 2016-02-04

Windows Security Applications (2007-12) permalink
(updated for Malwarebytes, 2016-02-04) When working with friend's PCs, here are some applications I install:

Secunia PSI Personal Software Inspector

soon be discontinued

(Added 2013-03-04) Filehippo Update Checker
(Added 2013-11-22) Colleagues also recommend Ninite
reviewed at The Register
Grisoft AVG free anti-virus
~~Lavasoft Ad-Aware~~ Not any more - see this article (2011-11-13)
Spybot-S&D
(added 2008-02-10) And one more link: Windows Sysinternals
(Added 2011-12-27) SANS ISC recommend MalwareBytes free anti-virus, OTOH: security issues,
(Added 2013-03-04) The UK government's advice

Tue, 2016-01-05

Hints on running a well-configured outgoing mail server. permalink

If you do not have a static IP address, use your ISP's mail relay (smarthost).
Make sure that there is a reverse DNS (PTR) record for your IP address. Make sure that it is not generic (e.g. wylie.me.uk, rather than client-12-34-56-78.adsl.example.org). You will need to contact your ISP to do this. (See RFC1912 section 2.1)
Make sure that doing a PTR lookup, then doing an A lookup on that domain name gives the original IP address, e.g.
```
$ host 82.68.155.89
89.155.68.82.in-addr.arpa domain name pointer wylie.me.uk.
$ host wylie.me.uk
wylie.me.uk has address 82.68.155.89
```
Get your ISP to SWIP your IP allocation, so that a whois lookup shows that it is allocated to you.
Make sure that your ISP has not listed your IP address as dynamic with any DNSBL, e.g. dul.dnsbl.sorbs.net. If necessary, get your ISP to contact the DNSBL maintainers and ask for your IP address to be delisted.
Make sure that your HELO/EHLO string is a FQDN (Fully Qualified Domain Name), e.g. "wylie.me.uk", rather than "NTSERVER", as required by RFC 2821 section 4.1.1.1

Further reading (This was originally written in 2006, some of these links may be out of date, I'm afraid):
SORBS
Spamhaus reverse DNS
Spamhaus Dynamic IP lists
Yahoo mail help
AOL Technical Standards for E-mail Delivery
AOL Reverse DNS
Messaging Anti-Abuse Working Group Sender Best Communications Practices

Sun, 2015-03-08

If you get errors trying to nfsmount your root partition during a PXE boot permalink

VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "nfs" or unknown-block(2,0): error -6
Please append a correct "root=" boot option; here are the available
partitions:
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)

try adding "nfsvers=3" to your kernel command line

LABEL alan
  KERNEL alan/bzImage
  APPEND root=/dev/nfs nfsroot=192.168.21.1:/work/netboot/alan/nfsroot,nfsvers=3 \
         ip=dhcp nfsrootdebug vga=0x323 netconsole=@192.168.21.201/,@192.168.21.2/

Thu, 2014-11-20

Gentoo, bash, xmalloc errors permalink
In Gentoo, after turning on the bash use-flag "mem-scramble", I got emerge errors for icu and nmap:


bash: xmalloc: shell.c:1596: cannot allocate 10 bytes (0 bytes allocated)

Fri, 2013-11-08

Just to try and g**gleb*mb it: permalink
Link to a friend's NHS Anti Smoking Campaign

Mon, 2013-02-18

Contact Me permalink

Please note that sending unsolicited marketing e-mail to an individual in the UK is an offence under Section 22 of the Privacy and Electronic Communications (EC Directive) Regulations 2003 http://www.legislation.gov.uk/uksi/2003/2426/regulation/22/made

If you are having difficulty e-mailing me, perhaps because of my anti-spam defenses, use this form (See also Hints on running a well-configured outgoing mail server )

A Panasonic Lumix DMC-TZ18 Camera

Contact me for the contents of the SD card and the return of the camera.

Sun, 2010-08-22

Lateral Cleft, Jingling Pot permalink
Photos