[dm-crypt] boot timeout and fsck.ext3

[dm-crypt] boot timeout and fsck.ext3

[Rainer Maier]

Hi all,
since my system is now working again, I have 2 more problems.

1. When Linux starts it requires a password for the encrypted 
partitions. How do I set the timeout value ?
I know there is an easy way to do it, but I did not find it any more.

2. When the system starts, it requests a fsck.ext3 check.
How is that done on luks ?

Best regards
Rainer

Re: [dm-crypt] boot timeout and fsck.ext3

[Jonas Meurer]

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hello,

On 13/08/2009 Rainer Maier wrote:
> since my system is now working again, I have 2 more problems.
> 
> 1. When Linux starts it requires a password for the encrypted
> partitions. How do I set the timeout value ?
> I know there is an easy way to do it, but I did not find it any more.

no, unfortunately there's no easy way to do it any longer. the timeout
option always had major drawbacks, such as fsck on boot failing in case
the dm-crypt device wasn't setup due to timeout. thus we completely
kicked the timeout option from cryptdisks in debian.

the way to go if you don't have physical access to your machine, is
adding the 'noauto' option in /etc/cryptdisks and decrypting the device
manually later with 'cryptdisks_start <device>'.

another option would be to use dropbear (small ssh server) within
initramfs to ssh into the machine while booting, and enter the
passphrase there. see debian bug #465902 [1] for more information.

> 2. When the system starts, it requests a fsck.ext3 check.
> How is that done on luks ?

fsck is run for the devices in /etc/fstab. you don't have the source
device of your encrypted partition in /etc/fstab, but rather the
decrypted target device. and that one contains the filesystem (i.e.
ext3). thus fsck runs a filesystem check on your decrypted filesystem,
just like it does for unencrypted partitions.
if the device doesn't exist (i.e. because cryptdisks init script failed)
then fsck fails on boot and an emergency shell is started. that's the
reason why we kicked timeout support from cryptdisks initscript in
debian (see above).

greetings,
 jonas

[1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=465902

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Re: [dm-crypt] boot timeout and fsck.ext3

[Rainer Maier]

Hi,
on my Debian installation I attached the noauto in /etc/crypttab:
tresor  /dev/sda2       none    luks,check=ext2,retry=5,timeout=5,noauto

and in fstab I only left:
/dev/mapper/tresor  /tresor         auto    defaults                   0       0
# /dev/sda2           /tresor         ext3    defaults,errors=remount-ro 0

Since only the /dev/sdb system is encrypted and not the /dev/hda or /dev/sda 
everything starts ok.

When I then use cryptdisks_start is seems equal to:
cryptsetup luksOpen /dev/sda2 tresor
but I have to mount the system manually:
mount /dev/mapper/tresor /tresor

Is that behaviour normal or do I have to change some settings to make
cryptdisks_start even mount the disks ?

Best regards
Rainer

Jonas Meurer schrieb:
> hello,
> 
> On 13/08/2009 Rainer Maier wrote:
>> since my system is now working again, I have 2 more problems.
>>
>> 1. When Linux starts it requires a password for the encrypted
>> partitions. How do I set the timeout value ?
>> I know there is an easy way to do it, but I did not find it any more.
> 
> no, unfortunately there's no easy way to do it any longer. the timeout
> option always had major drawbacks, such as fsck on boot failing in case
> the dm-crypt device wasn't setup due to timeout. thus we completely
> kicked the timeout option from cryptdisks in debian.
> 
> the way to go if you don't have physical access to your machine, is
> adding the 'noauto' option in /etc/cryptdisks and decrypting the device
> manually later with 'cryptdisks_start <device>'.
> 
> another option would be to use dropbear (small ssh server) within
> initramfs to ssh into the machine while booting, and enter the
> passphrase there. see debian bug #465902 [1] for more information.
> 
>> 2. When the system starts, it requests a fsck.ext3 check.
>> How is that done on luks ?
> 
> fsck is run for the devices in /etc/fstab. you don't have the source
> device of your encrypted partition in /etc/fstab, but rather the
> decrypted target device. and that one contains the filesystem (i.e.
> ext3). thus fsck runs a filesystem check on your decrypted filesystem,
> just like it does for unencrypted partitions.
> if the device doesn't exist (i.e. because cryptdisks init script failed)
> then fsck fails on boot and an emergency shell is started. that's the
> reason why we kicked timeout support from cryptdisks initscript in
> debian (see above).
> 
> greetings,
>  jonas
> 
> [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=465902
> 
> 
> ------------------------------------------------------------------------
> 
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> dm-crypt mailing list
> dm-crypt@saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt

Re: [dm-crypt] boot timeout and fsck.ext3

[Jonas Meurer]

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On 15/08/2009 Rainer Maier wrote:
> Hi,
> on my Debian installation I attached the noauto in /etc/crypttab:
> tresor  /dev/sda2       none    luks,check=ext2,retry=5,timeout=5,noauto
> 
> and in fstab I only left:
> /dev/mapper/tresor  /tresor         auto    defaults                   0       0
> # /dev/sda2           /tresor         ext3    defaults,errors=remount-ro 0
> 
> Since only the /dev/sdb system is encrypted and not the /dev/hda or
> /dev/sda everything starts ok.
> 
> When I then use cryptdisks_start is seems equal to:
> cryptsetup luksOpen /dev/sda2 tresor
> but I have to mount the system manually:
> mount /dev/mapper/tresor /tresor
> 
> Is that behaviour normal or do I have to change some settings to make
> cryptdisks_start even mount the disks ?

no, this is normal behaviour.

greetings,
 jonas

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Re: [dm-crypt] boot timeout and fsck.ext3

[Rainer Maier]

Hi Arno,
since only /dev/sdb is encrypted and /dev/hda and /dev/sda are not encrypted,
the system should have started just without this mount.

Regarding fsck.ext3, I usually left it to Linux when it started.
Would you have some hint how to do it manually ?
I.e. the steps to be performed or a page where I find a description.

Best regards
Rainer


Arno Wagner schrieb:
> On Thu, Aug 13, 2009 at 01:57:01PM +0200, Rainer Maier wrote:
>> Hi all,
>> since my system is now working again, I have 2 more problems.
>>
>> 1. When Linux starts it requires a password for the encrypted  
>> partitions. How do I set the timeout value ?
>> I know there is an easy way to do it, but I did not find it any more.
> 
> What do you want it to do if the timeout expires?
> Is this so the system can come up unattended?
> 
>> 2. When the system starts, it requests a fsck.ext3 check.
>> How is that done on luks ?
> 
> On the decrypted raw device.
> 
> Arno