Jeg fikk feilmeldinger ala:

[    2.957523] steal-ctty[125]: segfault at 0 ip 00007fbce02c4160 sp
00007ffe4dde3830 error 4 in libc.so.6[7fbce021f000+148000]
[    2.957551] Code: 8b e8 74 36 04 00 0f 1f 40 00 55 48 89 e5 41 57 41 56 41 55 41
54 53 48 83 ec 48 64 48 8b 04 25 28 00 00 00 48 89 45 c8 31 c0 <80> 3f 00 0f 84
47 01 00 00 49 89 f4 be 2f 00 00 00 48 89 fb 49 89
Segmentation fault
cat: can't open '/var/log/reopen-console': No such file or directory
rm: can't remove '/var/log/reopen-console': No such file or directory
touch: /var/run/brltty-Xorg: No such file or directory

Tok ikke vare på mine eksakte feilmeldinger, men jeg fant mailingliste-tråden https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=932149 om problemet, og med løsningen.

Selv om Debian er ganske gjærrig på CPU- og minnebruk, så viste det seg at jeg måtte sette “memory=1024M” i Xen-konfigurasjonen til den nye virtuelle serveren. Det holdt ikke med 512M.

Jeg endte opp med å installere fra CDROM-image med kernel og initrd fra https://deb.debian.org/debian/dists/Debian12.1/main/installer-amd64/current/images/cdrom/xen/.
Og med følgende XEN-node-konfigurasjon i /etc/xen/vm_srv-2023-1:

name = "srv-DEBIAN"

kernel  = "/xen/install-media/Debian12.1-installer-amd64-cdrom-xen/vmlinuz"
ramdisk = "/xen/install-media/Debian12.1-installer-amd64-cdrom-xen/initrd.gz"
extra   = "debian-installer/exit/always_halt=true -- console=hvc0 xencons=tty"

vcpus  = 1
memory = 1024

vif = [ 'mac=00:11:22:33:44:55,bridge=xenbr0' ]

disk = [
    'file:/xen/install-media/debian-12.1.0-amd64-netinst.iso,xvdd:cdrom,r',
    'phy:/dev/vg-data/xen-srv-DEBIAN-root,xvda,w',
    'phy:/dev/vg-data/xen-srv-DEBIAN-swap,xvdb,w'
]

on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'

I tried to tune log levels and found some tools lacking, such as “flac” and “lame”, but none of them fixed my problem, and still no explanation in the log files.

But I found something in the logs that led me in the right direction:

[16-08-29 23:03:04.3358] Slim::Player::TranscodingHelper::enabledFormat (209) Checking to see if wav-flc-*-* is enabled
[16-08-29 23:03:04.3360] Slim::Player::TranscodingHelper::checkBin (250)    enabled
[16-08-29 23:03:04.3362] Slim::Player::TranscodingHelper::checkBin (252)   Found command: [flac] -cs --totally-silent --compression-level-0 $START$ $END$ -- $FILE$ | [sox] -q -t flac - -t flac -C 0 $RESAMPLE$ -
[16-08-29 23:03:04.3364] Slim::Player::TranscodingHelper::getConvertCommand2 (446) Matched: wav->flc via: [flac] -cs --totally-silent --compression-level-0 $START$ $END$ -- $FILE$ | [sox] -q -t flac - -t flac -C 0 $RESAMPLE$ -

I was missing the “sox” tool!
So, I installed “sox”, and now the media server is properly encoding WAV/PCM audio files to FLAC (or something).

Jul  1 23:11:56 lance imapd: LOGIN, user=knut-olav@hoven.ws, ip=[::ffff:AAA.BBB.CCC.DDD], port=[48700], protocol=IMAP
Jul  1 23:11:56 lance imapd: knut-olav@hoven.ws: Permission denied

The solution was pretty simple.

The /tmp folder had bad permissions. This server was only meant for hosting email services, so bad permissions on /tmp folder was actually not an issue earlier.

I guess the wrong permissions were caused by my custom XEN node setup using multiple partitions, including a partition just for /tmp.

Debugging was quite hard

Authentication was successful, as I got a different error message when authenticating with a known bad password.

I debugged it using strace. It wasn’t easy, as courier imap forks out child processes for each connection, which I had to strace as well.

# strace /usr/sbin/couriertcpd -address=0 -maxprocs=40 -maxperip=20 -nodnslookup -noidentlookup 143 /usr/lib/courier/courier/imaplogin /usr/bin/imapd Maildir

Connect to port 143 using telnet.
Log in using this command:

i login MY_EMAIL_USERNAME MY_PASSWORD

Then find the imap process PID. Look for a process running as user vmail:

$ ps axuw|grep imapd
#...
vmail      362  0.0  1.0   4616  1344 ?        S    01:46   0:00 /usr/bin/imapd /var/spool/mail/vmail/hoven.ws/knut-olav/Maildir/
#...

In this case, the PID is 362. Then attach strace to it using strace -p 362, as sudo.

From the telnet interface, I entered a couple of commands like these:

2 select "INBOX"
5 UID fetch 1:10 (UID RFC822.SIZE FLAGS BODY.PEEK[HEADER.FIELDS (From To Cc Bcc Subject Date Message-ID Priority X-Priority References Newsgroups In-Reply-To Content-Type)])

Then I found this somewhere down into the strace output:

open("/tmp/tmpfWsezjv", O_RDWR|O_CREAT|O_EXCL, 0600) = -1 EACCES (Permission denied)
write(2, "ERR: knut-olav@hoven.ws: Permiss"..., 43) = 43

Fixing the problem
chmod 1777 /tmp

As I wrote earier… a simple solution.