Marek Mahut » howto

How to disable USB Disk STANDBY mode

marek — Tue, 03 Mar 2009 19:06:34 +0000

Recently I bought an external USB Disk Seagate FreeAgent XTreme, but after some idle time, it spanned down. Take me a while to find out how to disable this standby mode. First install sdparm.

If you want to start the drive in standby:

sdparm –command=start /dev/sdb

To clean standby mode flag:

sdparm –clear STANDBY -6 /dev/sdb && sdparm -a /dev/sdb

How to fix wrong dns serial number?

marek — Tue, 06 Jan 2009 14:57:07 +0000

Did it ever happen to you by mistake to add one additional digit into dns serial number? Ooops! Now, how to fix it?

Increase the serial number to (2^31) – (correct serial number) and reload named. For example 2^31-2009010602 = 138473046. As DNS serial numbers are signed integers, this make server thinks that it’s a negative number.
Set the serial number to 0 and reload.
Set the correct serial number and reload.
Voila!

Multiple host names in a single kerberos key tab

marek — Wed, 19 Nov 2008 12:33:55 +0000

If you are using clustered service with kerberos, you may want to merge hostnames keytab files to one for simple distribution.

Create host and service principals.

kadmin:  addprinc -randkey host/node1.corp.intranet.lan
kadmin:  addprinc -randkey host/node2.corp.intranet.lan
kadmin:  addprinc -randkey host/node3.corp.intranet.lan
kadmin:  addprinc -randkey host/node4.corp.intranet.lan
kadmin:  addprinc -randkey host/node5.corp.intranet.lan
kadmin:  addprinc -randkey host/node6.corp.intranet.lan
kadmin:  addprinc -randkey host/node7.corp.intranet.lan
kadmin:  addprinc -randkey host/node8.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node1.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node2.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node3.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node4.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node5.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node6.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node7.corp.intranet.lan
kadmin:  addprinc -randkey HTTP/node8.corp.intranet.lan

Save them to only one file (cluster.keytab).

kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node1.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node2.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node3.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node4.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node5.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node6.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node7.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab host/node8.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node1.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node2.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node3.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node4.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node5.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node6.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node7.corp.intranet.lan
kadmin:  ktadd -k /etc/httpd/cluster.keytab HTTP/node8.corp.intranet.lan

As alternative, you can use command ktutil if you already have a bunch of keytab files.

ktutil:  rkt /etc/krb5/node1.corp.intranet.lan.keytab
ktutil:  rkt /etc/krb5/node2.corp.intranet.lan.keytab
ktutil:  rkt /etc/krb5/node3.corp.intranet.lan.keytab
ktutil:  rkt /etc/krb5/node4.corp.intranet.lan.keytab
ktutil:  rkt /etc/krb5/node5.corp.intranet.lan.keytab
ktutil:  rkt /etc/krb5/node6.corp.intranet.lan.keytab
ktutil:  rkt /etc/krb5/node7.corp.intranet.lan.keytab
ktutil:  wkt /etc/cluster.keytab

Voila.

Fedora infrastructure Puppet training

marek — Sat, 20 Sep 2008 08:34:29 +0000

Mike McGrath, the Fedora infrastructure lead, made an awesome presentation on puppet and how to use it. Slides and audio record are posted at http://mmcgrath.fedorapeople.org/puppet/.

Sysadmin’s monday blues: clean your RPMs

marek — Mon, 14 Jul 2008 20:50:42 +0000

From time to time, I need to clean my disk from useless stuff I’ve installed over time. It’s just amazing how much of packages I can install during debugging and configuring every day. If I’m short of disk space, I start first by reviewing biggest packages on my system:

[mmahut@mmahut repo]$ rpm -qa --queryformat '%10{size} %{name}-%{version}\n' | sort -k1,1nr | head 317673868 fgfs-base-0.9.11 215271762 openoffice.org-core-2.3.0 133572466 frysk-0.4 120848879 fpc-2.2.0 89947314 glibc-common-2.7 80722817 java-1.7.0-icedtea-1.7.0.0 65310309 emacs-common-22.1 61516077 googleearth-4.2.198.2451 61036768 inkscape-0.46 60173188 tetex-fonts-3.0 [mmahut@mmahut repo]$

Another useful program is package-cleanup from package yum-utils. You can use it to list duplicates, orphans or problematic packages as well as old kernel packages.

[mmahut@mmahut ~]$ package-cleanup --orphans | head Setting up yum cinelerra-2.1-0.14.svn20071111.kwizart.fc8.i386 desktop-file-utils-0.15-2.fc8.i386 NetworkManager-0.7.0-0.6.7.svn3370.fc8.i386 bind-utils-9.5.0-27.rc1.fc8.i386 PackageKit-libs-0.1.5-0.351.20071126git.fc7.hughsie.i386 redmode-1.0-1.fc8.i386 kurso-3.0-1.fc8.i386 x11vnc-0.9.3-2.fc8.i386 popt-debuginfo-1.13-1.fc8.i386 [mmahut@mmahut ~]$

I’ve cleaned up 200MB today, great success!

How to hold a binocular

marek — Sun, 13 Apr 2008 08:12:08 +0000

I’ve found a very nice link explaining how to hold a binocular for sky observation. My preferable is number 3, but I’ve never tried fourth variant. You can also learn something about binocular mounts on that page.

How to make crypted /home under Fedora with lusk?

marek — Sat, 01 Dec 2007 18:39:15 +0000

There are tons of articles like this one on the internets, thus I’m just writing this down as my personal note. First let’s check for the package.

[root@mmahut ~]# rpm -qa cryptsetup-luks cryptsetup-luks-1.0.5-7.fc8 [root@mmahut ~]#

After un-mounting /and backing up :)/ our home directory, we need to erase everything on it.

[root@mmahut ~]# shred -n 5 -v /dev/vg00/lvhome shred: /dev/vg00/lvhome: pass 1/5 (random)... shred: /dev/vg00/lvhome: pass 1/5 (random)...13MiB/4.0GiB 0% shred: /dev/vg00/lvhome: pass 1/5 (random)...28MiB/4.0GiB 0% shred: /dev/vg00/lvhome: pass 1/5 (random)...43MiB/4.0GiB 1%

Don’t leave any chance.

[root@mmahut ~]# dd if=/dev/urandom of=/dev/vg00/lvhome bs=1024 478301+0 records in 478300+0 records out 489779200 bytes (490 MB) copied, 160.087 s, 3.1 MB/s [root@mmahut ~]#

Now, we can create a lusk head on your partition.

[root@mmahut ~]# cryptsetup luksFormat -c aes-cbc-essiv:sha256 -s 256 -y /dev/vg00/lvhome WARNING! ======== This will overwrite data on /dev/vg00/lvhome irrevocably. Are you sure? (Type uppercase yes): YES Enter LUKS passphrase: Verify passphrase: Command successful. [root@mmahut ~]#

We can check if we are able to de-crypt it.

[root@mmahut ~]# cryptsetup luksOpen /dev/vg00/lvhome home Enter LUKS passphrase: key slot 0 unlocked. Command successful. [root@mmahut ~]#

This will create new device file with name /dev/mapper/home, our decrypted media. You can safely create new file system on it now.

[root@mmahut ~]# mke2fs -j /dev/mapper/home mke2fs 1.40.2 (12-Jul-2007) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) ...

Migrate your data back and one last thing, don’t forget to change your fstab entry.

[root@mmahut ~]# grep home /etc/fstab #/dev/vg00/lvhome /home ext3 defaults 0 0 /dev/mapper/home /home ext3 defaults 0 0 [root@mmahut ~]# grep home /etc/crypttab home /dev/vg00/lvhome none [root@mmahut ~]#

htop – an interactive process viewer

marek — Tue, 11 Sep 2007 16:51:25 +0000

I’ve found an interesting tool, it’s an interactive process viewer called htop. Try it out, it’s very nice.

Linux Terminal Performance Comparison

marek — Thu, 06 Sep 2007 13:17:16 +0000

Martin Ankerl compares on his blog the performance of several linux terminals.

I’m happy user of gnome-terminal :)

The ext3cow File System

marek — Thu, 06 Sep 2007 13:05:26 +0000

While looking for more information about ext4 filesystem, I found an interesting patch named ext3cow. It is a versioning file system based on ext3. And how it works?

[root@storm ~]# echo "Beee" > ~/kac [root@storm ~]# snapshot Snapshot on .: 1062987103 [root@storm ~]# echo "Meeeee" > ~/kac [root@storm ~]# cat ~/kac@10629871034 Beee [root@storm ~]# ~/kac Meeeee [root@storm ~]#

Unfortunately, due to performance and storage overhead, consider it only as toy and not as production solution.