Alan Wylie's Web Site

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
< # Linux/x86 4.4.70 Kernel Configuration
> # Linux/x86 4.4.89 Kernel Configuration
< # CONFIG_PACKET is not set

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.


# 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
# 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:

Tue, 2016-01-05

Hints on running a well-configured outgoing mail server. permalink
  1. If you do not have a static IP address, use your ISP's mail relay (smarthost).

  2. Make sure that there is a reverse DNS (PTR) record for your IP address. Make sure that it is not generic (e.g., rather than 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 domain name pointer
    $ host has address

  3. Get your ISP to SWIP your IP allocation, so that a whois lookup shows that it is allocated to you.

  4. Make sure that your ISP has not listed your IP address as dynamic with any DNSBL, e.g. If necessary, get your ISP to contact the DNSBL maintainers and ask for your IP address to be delisted.

  5. Make sure that your HELO/EHLO string is a FQDN (Fully Qualified Domain Name), e.g. "", rather than "NTSERVER", as required by RFC 2821 section
Further reading (This was originally written in 2006, some of these links may be out of date, I'm afraid):
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
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=,nfsvers=3 \
         ip=dhcp nfsrootdebug vga=0x323 netconsole=@,@

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, 2013-03-18

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

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.


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

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 )

Please enter the text "spammers are scum" in this field:

Your Name:

Your Email:

Your Message:

Wed, 2012-12-19

Xmas links permalink
UWFRA SARDA BPC Gaping Gill Titan Titan Titan Titan

Sat, 2011-12-24

Captain Brown's Experience on board the barque Robert Hine permalink
My brother David has scanned in and OCR'd a pamphlet my Great^2 Grandfather published entitled Captain Brown's Experience on board the barque Robert Hine

Thu, 2011-11-10

Found, at the summit of Puig des Tossals Verts, Mallorca, on Wednesday 9th November 2011. permalink

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

Thu, 2010-05-06

Confusing Apache error message permalink

If you get the following error message:

[crit] [client] (13)Permission denied: /foo/bar/.htaccess pcfg_openfile: unable to check htaccess file, ensure it is readable, referer:

check that the permissions on the directory enable the web server user to read/access it, to fix it do something like:

find <dir> -type d | xargs chown <apache user>
find <dir> -type d | xargs chmod u+rx

Fri, 2010-02-26

I'm looking for a job. permalink

(Updated April 2010)
I've found a new job.

Sun, 2010-01-31

Links permalink

Weather maps

Some organisations I belong to:
The Vibram Mountaineering Club
The Karabiner Mountaineering Club
The Astronomy Centre

My excellent ISP: Zen Internet

A very nice Bed and Breakfast in Coniston:
Oaklands Guest House

And some of my favourite websites:
SANS - Internet Storm Center
The Register
Linux Weekly News
National Secular Society

The Spamhaus Project

ROCK Linux
Gentoo Linux

Abstruse Goose
User Friendly
The Joy of Tech
Irregular Webcomic!
Questionable Content
Something Positive
Full Frontal Nerdity

Astronomy Picture of the Day

Tue, 2010-01-05

Unsolicited Bulk Commercial e-mail from Janglemail / Blurbjangle permalink

Full story here