Tugriceri Web Notes

Linux

Dovecot Error

by on Dec.26, 2007, under Mail

imap-login: imap-login: error while loading shared libraries: libsepol.so.1: failed to map segment from shared object: Cannot allocate memory

64 bitlik bir sistem üzerinde dovecot ta imap ile ssl i aktif ettiğim zaman üstteki uyarıyı alıyordum.  Problemin çözümü için /etc/dovecot.conf dosyası içerisinden;

“login_process_size = 32” olan değeri “login_process_size = 64” olarak değiştirmek yeterli.

Dovecot.conf içerisindeki açıklama ;

# Set max. process size in megabytes. If you don’t use
# login_process_per_connection you might need to grow this.

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Fetchmail example

by on Dec.24, 2007, under Mail

Example .fetchmailrc file ;

[root@mail Maildir]# cat /root/.fetchmailrc

defaults
    fetchall
    keep
set no bouncemail

poll 127.0.0.1 protocol IMAP
    user efsaneuser@superdomain.com there with password xxxxx is efsane.user@superdomain.com here
    smtphost 192.168.0.10
———————————————–
if you want to fetch old mails with subfolders, you can try this settings.

[root@mail Maildir]# cat /root/fet.sh

for gonder in “INBOX.Ocak” “INBOX.Subat” “INBOX.Mart” “INBOX.Nisan” “INBOX.Mayis” “INBOX.Haziran” “INBOX.Temmuz” “INBOX.Agustos” “INBOX.Eylul” “INBOX.Kasim” “INBOX.Aralik”
do
fetchmail -r $gonder
done

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Qmail time stamps

by on Nov.19, 2007, under Mail

tai64nlocal Qmail log larındaki TAI64N timestamp değerlerini okunabilir formata çevirmektedir.

Örnek olarak ;

[root@mail smtp]# echo “@4000000037c219bf2ef02e94” | tai64nlocal
1999-08-24 07:04:05.787492500

cat @4000000047414fa33437fd14.s | tai64nlocal

şeklindede kullanılabilir.

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smtp-auth test with telnet

by on Sep.16, 2007, under Linux

$wget http://www.infocopter.com/know-how/bin/mimencode
$mv mimencode /bin
$chmod 755 /bin/mimencode

$ echo “user@domain.com\0user@domain.com\0password” | mimencode
dXNlckBkb21haW4uY29tXDB1c2VyQGRvbWFpbi5jb21cMHBhc3N3b3JkCg==

$telnet localhost 25

auth plain dXNlckBkb21haW4uY29tXDB1c2VyQGRvbWFpbi5jb21cMHBhc3N3b3JkCg==

235 ok, go ahead (#2.0.0)

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Qmail finding configuration problems

by on Sep.15, 2007, under Linux

Life with qmail

It sometimes helps to run a service manually in order to find configuration problems. For example, if your qmail-smtpd/log service isn’t running, do:

cd /service/qmail-smtpd/log
svc -d .
./run
if no errors, enter a line of text and press ENTER
if still no errors, enter CTRL-D (end of file)

At this point, you should be able to identify the problem and fix it. Once that’s done, return to the service’s directory, if necessary, and do:

svc -u .

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File Systems form Gentoo page

by on Sep.13, 2007, under Linux

Gentoo Linux Documentation — Preparing the Disks

Filesystems?The Linux kernel supports various filesystems. We’ll explain ext2, ext3, ReiserFS, XFS and JFS as these are the most commonly used filesystems on Linux systems.

ext2 is the tried and true Linux filesystem but doesn’t have metadata journaling, which means that routine ext2 filesystem checks at startup time can be quite time-consuming. There is now quite a selection of newer-generation journaled filesystems that can be checked for consistency very quickly and are thus generally preferred over their non-journaled counterparts. Journaled filesystems prevent long delays when you boot your system and your filesystem happens to be in an inconsistent state.

ext3 is the journaled version of the ext2 filesystem, providing metadata journaling for fast recovery in addition to other enhanced journaling modes like full data and ordered data journaling. It uses an HTree index that enables high performance in almost all situations. In short, ext3 is a very good and reliable filesystem.

ReiserFS is a B+tree-based filesystem that has very good overall performance and greatly outperforms both ext2 and ext3 when dealing with small files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales extremely well and has metadata journaling. ReiserFS is solid and usable as both general-purpose filesystem and for extreme cases such as the creation of large filesystems, very large files and directories containing tens of thousands of small files.

XFS is a filesystem with metadata journaling which comes with a robust feature-set and is optimized for scalability. We only recommend using this filesystem on Linux systems with high-end SCSI and/or fibre channel storage and an uninterruptible power supply. Because XFS aggressively caches in-transit data in RAM, improperly designed programs (those that don’t take proper precautions when writing files to disk and there are quite a few of them) can lose a good deal of data if the system goes down unexpectedly.

JFS is IBM’s high-performance journaling filesystem. It has recently become production-ready and there hasn’t been a sufficient track record to comment positively nor negatively on its general stability at this point.

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Gentoo Telnet

by on Sep.12, 2007, under Linux

emerge telnet-bsd

Pro-Linux Sicherheitsservice: Gentoo – telnet-bsd

The telnet-bsd telnet client is vulnerable to two buffer overflows, which could allow a malicious telnet server operator to execute arbitrary code.

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proc mounts etc mtab

by on Sep.12, 2007, under Linux

live cd src# grub-install /dev/hda
df: warning:cannot read table of mounted filesystems:no such file or directory
df: warning:cannot read table of mounted filesystems:no such file or directory
could not find device /boot: not found or not a block device

chroot olduktan sonra;

live cd src#  grep -v rootfs /proc/mounts > /etc/mtab


Komutu çalıştırılmalı.

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Proc dev mount and chroot

by on Sep.12, 2007, under Linux

srv# mount -t proc none /mnt/gentoo/proc
srv# mount -o bind /dev /mnt/gentoo/dev
srv# chroot
/mnt/gentoo /bin/bash
srv# env-update && source /etc/profile

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Authenticating E-Mail

by on Sep.11, 2007, under Spam

http://www.ietf.org/rfc/rfc4406.txt

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iptables ile Port Knocking

by on Sep.11, 2007, under Linux

               $IPTABLES -A INPUT -p tcp –dport 22   -m recent –rcheck
–seconds 60 –name SSH          -j ACCEPT
                $IPTABLES -A INPUT
-p tcp –dport 21   -m recent –rcheck –seconds 60 –name SSH          -j
ACCEPT
                $IPTABLES -A INPUT -p tcp –dport 1599 -m
recent –name SSH –remove -j DROP
               
$IPTABLES -A INPUT -p tcp –dport 1600 -m recent –name
SSH –set    -j DROP
                $IPTABLES -A INPUT -p tcp –dport 1601
-m recent –name SSH –remove -j DROP

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RPM-PGP-KEY import

by on Sep.11, 2007, under Linux

RPM-PGP-KEY import 

 rpm –import /usr/share/doc/rpm-4.4.2/RPM-PGP-KEY

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Mysql user priv.

by on Sep.11, 2007, under Mysql

mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'localhost'
-> IDENTIFIED BY 'some_pass' WITH GRANT OPTION;

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