Re: Changing the name of a compressed file

[Aki Tuomi]

There is global mail_plugins variable, you just have to be careful not to 
overwrite it somewhere.

Aki

> On June 11, 2017 at 2:46 PM Peter West  wrote:
> 
> 
> It looks as though there is no global mail_plugins variable.  Is this the 
> case?  Or have I misunderstood how global variable are expressed?
> 
> P
> 
> > On 10 Jun 2017, at 9:10 pm, Peter West  wrote:
> > 
> > Ok, I added zlib to imap protocol.
> > 
> > protocol imap {
> >  …
> >  mail_plugins = $mail_plugins zlib
> > }
> > 
> > Now both imap and lmtp protocols have zlib plugin enabled, and both send 
> > and receive mail is compressed.
> > 
> > Peter
> > 
> >> On 10 Jun 2017, at 6:50 pm, Aki Tuomi  wrote:
> >> 
> >> Please check that you are not overwriting mail plugins for lmtp. Or post 
> >> your doveconf -n.
> >> 
> >> Aki
> >> 
> >>> On June 10, 2017 at 11:10 AM Peter West  wrote:
> >>> 
> >>> 
> >>> Not sure what you mean. I’m using lmtp to send messages to Dovecot from 
> >>> Postfix.
> >>> 
>  On 10 Jun 2017, at 6:08 pm, Aki Tuomi  wrote:
>  
>  What's your LDA?
>  
>  Aki
>  
> > On June 10, 2017 at 11:01 AM Peter West  wrote:
> > 
> > 
> > Thanks for that Aki.
> > 
> > Follow-up question.  I tried to initiate compression by adding
> > 
> > mail_plugins = $mail_plugins zlib
> > 
> > plugin {
> >  zlib_save_level = 6
> >  zlib_save = xz
> > }
> > 
> > 
> > to dovecot.conf.  I restarted dovecot and sent one message to the 
> > server, and one message from the server.  Neither was compressed.  I 
> > changed the save type to
> > 
> >  zlib_save = bz2
> > 
> > and repeated. This time the message received (in 
> > /var/vmail///cur) was not compressed, but the message 
> > in /var/vmail///.Sent/cur was bzip2 compressed.
> > 
> > Why is the received mail not being compressed?  Is this the point of 
> > the discussion about compressing old mails?
> > 
> > 
> >> On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
> >> 
> >> 
> >>> On June 10, 2017 at 5:58 AM Peter West  wrote:
> >>> 
> >>> 
> >>> Concerning Maildir, the wiki page on compression has this:
> >>> 
> >>> All mails must have ,S= in their filename where  contains 
> >>> the original uncompressed mail size, otherwise there will be problems 
> >>> with quota calculation as well as other potential random failures. 
> >>> Note that if the filename doesn’t contain the ,S= before 
> >>> compression, adding it afterwards changes the base filename and thus 
> >>> the message UID. The safest thing to do is simply to not compress 
> >>> such files.
> >>> 
> >>> Further down on the same page is this:
> >>> 
> >>> If the file does exist, rename() (mv) the compressed file over the 
> >>> original file.
> >>>   • Dovecot can now read the file, but to avoid compressing it 
> >>> again on the next run, you'll probably want to rename it again to 
> >>> include e.g. a "Z" flag in the file name to mark that it was 
> >>> compressed (e.g. 1223212411.M907959P17184.host,S=3271:2,SZ).
> >>> 
> >>> These comments seem to contradict each. Or is there a difference 
> >>> between adding the size specifier to the filename and adding a Z flag 
> >>> to the end of the file name?
> >>> 
> >>> --
> >>> Peter West
> >>> p...@pbw.id.au
> >>> And the great throng heard him gladly.
> >>> 
> >> 
> >> Keyword is 'base filename'. From the wiki, "The standard filename 
> >> definition is: ":2,".". Z is a flag.
> >> 
> >> Aki
> > 
> >>> 
> > 
>

Re: Changing the name of a compressed file

[Peter West]

It looks as though there is no global mail_plugins variable.  Is this the case? 
 Or have I misunderstood how global variable are expressed?

P

> On 10 Jun 2017, at 9:10 pm, Peter West  wrote:
> 
> Ok, I added zlib to imap protocol.
> 
> protocol imap {
>  …
>  mail_plugins = $mail_plugins zlib
> }
> 
> Now both imap and lmtp protocols have zlib plugin enabled, and both send and 
> receive mail is compressed.
> 
> Peter
> 
>> On 10 Jun 2017, at 6:50 pm, Aki Tuomi  wrote:
>> 
>> Please check that you are not overwriting mail plugins for lmtp. Or post 
>> your doveconf -n.
>> 
>> Aki
>> 
>>> On June 10, 2017 at 11:10 AM Peter West  wrote:
>>> 
>>> 
>>> Not sure what you mean. I’m using lmtp to send messages to Dovecot from 
>>> Postfix.
>>> 
 On 10 Jun 2017, at 6:08 pm, Aki Tuomi  wrote:
 
 What's your LDA?
 
 Aki
 
> On June 10, 2017 at 11:01 AM Peter West  wrote:
> 
> 
> Thanks for that Aki.
> 
> Follow-up question.  I tried to initiate compression by adding
> 
> mail_plugins = $mail_plugins zlib
> 
> plugin {
>  zlib_save_level = 6
>  zlib_save = xz
> }
> 
> 
> to dovecot.conf.  I restarted dovecot and sent one message to the server, 
> and one message from the server.  Neither was compressed.  I changed the 
> save type to
> 
>  zlib_save = bz2
> 
> and repeated. This time the message received (in 
> /var/vmail///cur) was not compressed, but the message in 
> /var/vmail///.Sent/cur was bzip2 compressed.
> 
> Why is the received mail not being compressed?  Is this the point of the 
> discussion about compressing old mails?
> 
> 
>> On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
>> 
>> 
>>> On June 10, 2017 at 5:58 AM Peter West  wrote:
>>> 
>>> 
>>> Concerning Maildir, the wiki page on compression has this:
>>> 
>>> All mails must have ,S= in their filename where  contains 
>>> the original uncompressed mail size, otherwise there will be problems 
>>> with quota calculation as well as other potential random failures. Note 
>>> that if the filename doesn’t contain the ,S= before compression, 
>>> adding it afterwards changes the base filename and thus the message 
>>> UID. The safest thing to do is simply to not compress such files.
>>> 
>>> Further down on the same page is this:
>>> 
>>> If the file does exist, rename() (mv) the compressed file over the 
>>> original file.
>>> • Dovecot can now read the file, but to avoid compressing it 
>>> again on the next run, you'll probably want to rename it again to 
>>> include e.g. a "Z" flag in the file name to mark that it was compressed 
>>> (e.g. 1223212411.M907959P17184.host,S=3271:2,SZ).
>>> 
>>> These comments seem to contradict each. Or is there a difference 
>>> between adding the size specifier to the filename and adding a Z flag 
>>> to the end of the file name?
>>> 
>>> --
>>> Peter West
>>> p...@pbw.id.au
>>> And the great throng heard him gladly.
>>> 
>> 
>> Keyword is 'base filename'. From the wiki, "The standard filename 
>> definition is: ":2,".". Z is a flag.
>> 
>> Aki
> 
>>> 
> 



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Re: Changing the name of a compressed file

[Peter West]

Ok, I added zlib to imap protocol.

protocol imap {
  …
  mail_plugins = $mail_plugins zlib
}

Now both imap and lmtp protocols have zlib plugin enabled, and both send and 
receive mail is compressed.

Peter

> On 10 Jun 2017, at 6:50 pm, Aki Tuomi  wrote:
> 
> Please check that you are not overwriting mail plugins for lmtp. Or post your 
> doveconf -n.
> 
> Aki
> 
>> On June 10, 2017 at 11:10 AM Peter West  wrote:
>> 
>> 
>> Not sure what you mean. I’m using lmtp to send messages to Dovecot from 
>> Postfix.
>> 
>>> On 10 Jun 2017, at 6:08 pm, Aki Tuomi  wrote:
>>> 
>>> What's your LDA?
>>> 
>>> Aki
>>> 
 On June 10, 2017 at 11:01 AM Peter West  wrote:
 
 
 Thanks for that Aki.
 
 Follow-up question.  I tried to initiate compression by adding
 
 mail_plugins = $mail_plugins zlib
 
 plugin {
   zlib_save_level = 6
   zlib_save = xz
 }
 
 
 to dovecot.conf.  I restarted dovecot and sent one message to the server, 
 and one message from the server.  Neither was compressed.  I changed the 
 save type to
 
   zlib_save = bz2
 
 and repeated. This time the message received (in 
 /var/vmail///cur) was not compressed, but the message in 
 /var/vmail///.Sent/cur was bzip2 compressed.
 
 Why is the received mail not being compressed?  Is this the point of the 
 discussion about compressing old mails?
 
 
> On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
> 
> 
>> On June 10, 2017 at 5:58 AM Peter West  wrote:
>> 
>> 
>> Concerning Maildir, the wiki page on compression has this:
>> 
>> All mails must have ,S= in their filename where  contains 
>> the original uncompressed mail size, otherwise there will be problems 
>> with quota calculation as well as other potential random failures. Note 
>> that if the filename doesn’t contain the ,S= before compression, 
>> adding it afterwards changes the base filename and thus the message UID. 
>> The safest thing to do is simply to not compress such files.
>> 
>> Further down on the same page is this:
>> 
>> If the file does exist, rename() (mv) the compressed file over the 
>> original file.
>>  • Dovecot can now read the file, but to avoid compressing it again on 
>> the next run, you'll probably want to rename it again to include e.g. a 
>> "Z" flag in the file name to mark that it was compressed (e.g. 
>> 1223212411.M907959P17184.host,S=3271:2,SZ).
>> 
>> These comments seem to contradict each. Or is there a difference between 
>> adding the size specifier to the filename and adding a Z flag to the end 
>> of the file name?
>> 
>> --
>> Peter West
>> p...@pbw.id.au
>> And the great throng heard him gladly.
>> 
> 
> Keyword is 'base filename'. From the wiki, "The standard filename 
> definition is: ":2,".". Z is a flag.
> 
> Aki
 
>> 



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Re: Changing the name of a compressed file

[Peter West]

Well spotted.

In my first attempt, the configuration I originally posted was at the end of my 
dovecot.conf file, and I was not including the conf.d configuration files. 
Preceding that was my lmtp protocol cong.

protocol lmtp {
  postmaster_address = postmaster
  # Space separated list of plugins to load (default is global mail_plugins).
  mail_plugins = $mail_plugins sieve
}

 
 mail_plugins = $mail_plugins zlib
 
 plugin {
   zlib_save_level = 6
   zlib_save = xz
 }
 


The doveconf -n associated with this is as follows:

01  # 2.2.22 (fe789d2): /etc/dovecot/dovecot.conf
02  # Pigeonhole version 0.4.13 (7b14904)
03  # OS: Linux 4.9.15-x86_64-linode81 x86_64 Ubuntu 16.04.2 LTS
04  auth_mechanisms = plain login
05  log_timestamp = "%Y-%m-%d %H:%M:%S "
06  mail_gid = vmail
07  mail_home = maildir:/var/vmail/%d/%n
08  mail_location = maildir:~/Maildir
09
10  mail_privileged_group = vmail
11  mail_uid = vmail
12  managesieve_notify_capability = mailto
13  managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric relational 
regex imap4flags copy include variables body enotify environment mailbox date 
ihave
14  namespace inbox {
15inbox = yes
16location =
17mailbox Archive {
18  auto = subscribe
19  special_use = \Archive
20}
21mailbox Drafts {
22  auto = subscribe
23  special_use = \Drafts
24}
25mailbox Sent {
26  auto = subscribe
27  special_use = \Sent
28}
29mailbox Spam {
30  auto = subscribe
31  special_use = \Junk
32}
33mailbox Trash {
34  auto = subscribe
35  special_use = \Trash
36}
37prefix =
38  }
39  passdb {
40args = /etc/dovecot/dovecot-sql.conf.ext
41driver = sql
42  }
43  plugin {
44sieve = ~/.dovecot.sieve
45sieve_dir = ~/sieve
46zlib_save = bz2
47zlib_save_level = 6
48  }
49  protocols = " imap lmtp sieve"
50  service auth {
51unix_listener /var/spool/postfix/private/dovecot-auth {
52  group = postfix
53  mode = 0660
54  user = postfix
55}
56user = root
57  }
58  service lmtp {
59unix_listener /var/spool/postfix/private/dovecot-lmtp {
60  group = postfix
61  mode = 0600
62  user = postfix
63}
64  }
65  ssl_ca = >>> mail_plugins = $mail_plugins zlib

The resulting doveconf -n is:

01  # 2.2.22 (fe789d2): /etc/dovecot/dovecot.conf
02  # Pigeonhole version 0.4.13 (7b14904)
03  # OS: Linux 4.9.15-x86_64-linode81 x86_64 Ubuntu 16.04.2 LTS
04  auth_mechanisms = plain login
05  log_timestamp = "%Y-%m-%d %H:%M:%S "
06  mail_gid = vmail
07  mail_home = maildir:/var/vmail/%d/%n
08  mail_location = maildir:~/Maildir
09  mail_plugins = " zlib"
10  mail_privileged_group = vmail
11  mail_uid = vmail
12  managesieve_notify_capability = mailto
13  managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric relational 
regex imap4flags copy include variables body enotify environment mailbox date 
ihave
14  namespace inbox {
15inbox = yes
16location =
17mailbox Archive {
18  auto = subscribe
19  special_use = \Archive
20}
21mailbox Drafts {
22  auto = subscribe
23  special_use = \Drafts
24}
25mailbox Sent {
26  auto = subscribe
27  special_use = \Sent
28}
29mailbox Spam {
30  auto = subscribe
31  special_use = \Junk
32}
33mailbox Trash {
34  auto = subscribe
35  special_use = \Trash
36}
37prefix =
38  }
39  passdb {
40args = /etc/dovecot/dovecot-sql.conf.ext
41driver = sql
42  }
43  plugin {
44sieve = ~/.dovecot.sieve
45sieve_dir = ~/sieve
46zlib_save = bz2
47zlib_save_level = 6
48  }
49  protocols = " imap lmtp sieve"
50  service auth {
51unix_listener /var/spool/postfix/private/dovecot-auth {
52  group = postfix
53  mode = 0660
54  user = postfix
55}
56user = root
57  }
58  service lmtp {
59unix_listener /var/spool/postfix/private/dovecot-lmtp {
60  group = postfix
61  mode = 0600
62  user = postfix
63}
64  }
65  ssl_ca = //cur are compressed;
sent messages in /var/vmail///.Sent/cur are not compressed.

I assume that I need both specifications.
--
Peter West
p...@pbw.id.au
And the great throng heard him gladly.


> On 10 Jun 2017, at 6:50 pm, Aki Tuomi  wrote:
> 
> Please check that you are not overwriting 

Re: Changing the name of a compressed file

[Aki Tuomi]

Please check that you are not overwriting mail plugins for lmtp. Or post your 
doveconf -n.

Aki

> On June 10, 2017 at 11:10 AM Peter West  wrote:
> 
> 
> Not sure what you mean. I’m using lmtp to send messages to Dovecot from 
> Postfix.
> 
> > On 10 Jun 2017, at 6:08 pm, Aki Tuomi  wrote:
> > 
> > What's your LDA?
> > 
> > Aki
> > 
> >> On June 10, 2017 at 11:01 AM Peter West  wrote:
> >> 
> >> 
> >> Thanks for that Aki.
> >> 
> >> Follow-up question.  I tried to initiate compression by adding
> >> 
> >> mail_plugins = $mail_plugins zlib
> >> 
> >> plugin {
> >>zlib_save_level = 6
> >>zlib_save = xz
> >> }
> >> 
> >> 
> >> to dovecot.conf.  I restarted dovecot and sent one message to the server, 
> >> and one message from the server.  Neither was compressed.  I changed the 
> >> save type to
> >> 
> >>zlib_save = bz2
> >> 
> >> and repeated. This time the message received (in 
> >> /var/vmail///cur) was not compressed, but the message in 
> >> /var/vmail///.Sent/cur was bzip2 compressed.
> >> 
> >> Why is the received mail not being compressed?  Is this the point of the 
> >> discussion about compressing old mails?
> >> 
> >> 
> >>> On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
> >>> 
> >>> 
>  On June 10, 2017 at 5:58 AM Peter West  wrote:
>  
>  
>  Concerning Maildir, the wiki page on compression has this:
>  
>  All mails must have ,S= in their filename where  contains 
>  the original uncompressed mail size, otherwise there will be problems 
>  with quota calculation as well as other potential random failures. Note 
>  that if the filename doesn’t contain the ,S= before compression, 
>  adding it afterwards changes the base filename and thus the message UID. 
>  The safest thing to do is simply to not compress such files.
>  
>  Further down on the same page is this:
>  
>  If the file does exist, rename() (mv) the compressed file over the 
>  original file.
>   • Dovecot can now read the file, but to avoid compressing it again on 
>  the next run, you'll probably want to rename it again to include e.g. a 
>  "Z" flag in the file name to mark that it was compressed (e.g. 
>  1223212411.M907959P17184.host,S=3271:2,SZ).
>  
>  These comments seem to contradict each. Or is there a difference between 
>  adding the size specifier to the filename and adding a Z flag to the end 
>  of the file name?
>  
>  --
>  Peter West
>  p...@pbw.id.au
>  And the great throng heard him gladly.
>  
> >>> 
> >>> Keyword is 'base filename'. From the wiki, "The standard filename 
> >>> definition is: ":2,".". Z is a flag.
> >>> 
> >>> Aki
> >> 
>

Re: Changing the name of a compressed file

[Peter West]

Not sure what you mean. I’m using lmtp to send messages to Dovecot from Postfix.

> On 10 Jun 2017, at 6:08 pm, Aki Tuomi  wrote:
> 
> What's your LDA?
> 
> Aki
> 
>> On June 10, 2017 at 11:01 AM Peter West  wrote:
>> 
>> 
>> Thanks for that Aki.
>> 
>> Follow-up question.  I tried to initiate compression by adding
>> 
>> mail_plugins = $mail_plugins zlib
>> 
>> plugin {
>>zlib_save_level = 6
>>zlib_save = xz
>> }
>> 
>> 
>> to dovecot.conf.  I restarted dovecot and sent one message to the server, 
>> and one message from the server.  Neither was compressed.  I changed the 
>> save type to
>> 
>>zlib_save = bz2
>> 
>> and repeated. This time the message received (in 
>> /var/vmail///cur) was not compressed, but the message in 
>> /var/vmail///.Sent/cur was bzip2 compressed.
>> 
>> Why is the received mail not being compressed?  Is this the point of the 
>> discussion about compressing old mails?
>> 
>> 
>>> On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
>>> 
>>> 
 On June 10, 2017 at 5:58 AM Peter West  wrote:
 
 
 Concerning Maildir, the wiki page on compression has this:
 
 All mails must have ,S= in their filename where  contains the 
 original uncompressed mail size, otherwise there will be problems with 
 quota calculation as well as other potential random failures. Note that if 
 the filename doesn’t contain the ,S= before compression, adding it 
 afterwards changes the base filename and thus the message UID. The safest 
 thing to do is simply to not compress such files.
 
 Further down on the same page is this:
 
 If the file does exist, rename() (mv) the compressed file over the 
 original file.
• Dovecot can now read the file, but to avoid compressing it again on 
 the next run, you'll probably want to rename it again to include e.g. a 
 "Z" flag in the file name to mark that it was compressed (e.g. 
 1223212411.M907959P17184.host,S=3271:2,SZ).
 
 These comments seem to contradict each. Or is there a difference between 
 adding the size specifier to the filename and adding a Z flag to the end 
 of the file name?
 
 --
 Peter West
 p...@pbw.id.au
 And the great throng heard him gladly.
 
>>> 
>>> Keyword is 'base filename'. From the wiki, "The standard filename 
>>> definition is: ":2,".". Z is a flag.
>>> 
>>> Aki
>> 



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Re: Changing the name of a compressed file

[Aki Tuomi]

What's your LDA?

Aki

> On June 10, 2017 at 11:01 AM Peter West  wrote:
> 
> 
> Thanks for that Aki.
> 
> Follow-up question.  I tried to initiate compression by adding
> 
> mail_plugins = $mail_plugins zlib
> 
> plugin {
> zlib_save_level = 6
> zlib_save = xz
> }
> 
> 
> to dovecot.conf.  I restarted dovecot and sent one message to the server, and 
> one message from the server.  Neither was compressed.  I changed the save 
> type to
> 
> zlib_save = bz2
> 
> and repeated. This time the message received (in 
> /var/vmail///cur) was not compressed, but the message in 
> /var/vmail///.Sent/cur was bzip2 compressed.
> 
> Why is the received mail not being compressed?  Is this the point of the 
> discussion about compressing old mails?
> 
> 
> > On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
> > 
> > 
> >> On June 10, 2017 at 5:58 AM Peter West  wrote:
> >> 
> >> 
> >> Concerning Maildir, the wiki page on compression has this:
> >> 
> >> All mails must have ,S= in their filename where  contains the 
> >> original uncompressed mail size, otherwise there will be problems with 
> >> quota calculation as well as other potential random failures. Note that if 
> >> the filename doesn’t contain the ,S= before compression, adding it 
> >> afterwards changes the base filename and thus the message UID. The safest 
> >> thing to do is simply to not compress such files.
> >> 
> >> Further down on the same page is this:
> >> 
> >> If the file does exist, rename() (mv) the compressed file over the 
> >> original file.
> >>• Dovecot can now read the file, but to avoid compressing it again on 
> >> the next run, you'll probably want to rename it again to include e.g. a 
> >> "Z" flag in the file name to mark that it was compressed (e.g. 
> >> 1223212411.M907959P17184.host,S=3271:2,SZ).
> >> 
> >> These comments seem to contradict each. Or is there a difference between 
> >> adding the size specifier to the filename and adding a Z flag to the end 
> >> of the file name?
> >> 
> >> --
> >> Peter West
> >> p...@pbw.id.au
> >> And the great throng heard him gladly.
> >> 
> > 
> > Keyword is 'base filename'. From the wiki, "The standard filename 
> > definition is: ":2,".". Z is a flag.
> > 
> > Aki
>

Re: Changing the name of a compressed file

[Peter West]

Thanks for that Aki.

Follow-up question.  I tried to initiate compression by adding

mail_plugins = $mail_plugins zlib

plugin {
zlib_save_level = 6
zlib_save = xz
}


to dovecot.conf.  I restarted dovecot and sent one message to the server, and 
one message from the server.  Neither was compressed.  I changed the save type 
to

zlib_save = bz2

and repeated. This time the message received (in 
/var/vmail///cur) was not compressed, but the message in 
/var/vmail///.Sent/cur was bzip2 compressed.

Why is the received mail not being compressed?  Is this the point of the 
discussion about compressing old mails?


> On 10 Jun 2017, at 4:43 pm, Aki Tuomi  wrote:
> 
> 
>> On June 10, 2017 at 5:58 AM Peter West  wrote:
>> 
>> 
>> Concerning Maildir, the wiki page on compression has this:
>> 
>> All mails must have ,S= in their filename where  contains the 
>> original uncompressed mail size, otherwise there will be problems with quota 
>> calculation as well as other potential random failures. Note that if the 
>> filename doesn’t contain the ,S= before compression, adding it 
>> afterwards changes the base filename and thus the message UID. The safest 
>> thing to do is simply to not compress such files.
>> 
>> Further down on the same page is this:
>> 
>> If the file does exist, rename() (mv) the compressed file over the original 
>> file.
>>  • Dovecot can now read the file, but to avoid compressing it again on 
>> the next run, you'll probably want to rename it again to include e.g. a "Z" 
>> flag in the file name to mark that it was compressed (e.g. 
>> 1223212411.M907959P17184.host,S=3271:2,SZ).
>> 
>> These comments seem to contradict each. Or is there a difference between 
>> adding the size specifier to the filename and adding a Z flag to the end of 
>> the file name?
>> 
>> --
>> Peter West
>> p...@pbw.id.au
>> And the great throng heard him gladly.
>> 
> 
> Keyword is 'base filename'. From the wiki, "The standard filename definition 
> is: ":2,".". Z is a flag.
> 
> Aki



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Re: Changing the name of a compressed file

[Aki Tuomi]

> On June 10, 2017 at 5:58 AM Peter West  wrote:
> 
> 
> Concerning Maildir, the wiki page on compression has this:
> 
> All mails must have ,S= in their filename where  contains the 
> original uncompressed mail size, otherwise there will be problems with quota 
> calculation as well as other potential random failures. Note that if the 
> filename doesn’t contain the ,S= before compression, adding it 
> afterwards changes the base filename and thus the message UID. The safest 
> thing to do is simply to not compress such files.
> 
> Further down on the same page is this:
> 
> If the file does exist, rename() (mv) the compressed file over the original 
> file.
>   • Dovecot can now read the file, but to avoid compressing it again on 
> the next run, you'll probably want to rename it again to include e.g. a "Z" 
> flag in the file name to mark that it was compressed (e.g. 
> 1223212411.M907959P17184.host,S=3271:2,SZ).
> 
> These comments seem to contradict each. Or is there a difference between 
> adding the size specifier to the filename and adding a Z flag to the end of 
> the file name?
> 
> --
> Peter West
> p...@pbw.id.au
> And the great throng heard him gladly.
>

Keyword is 'base filename'. From the wiki, "The standard filename definition 
is: ":2,".". Z is a flag.

Aki

Changing the name of a compressed file

[Peter West]

Concerning Maildir, the wiki page on compression has this:

All mails must have ,S= in their filename where  contains the 
original uncompressed mail size, otherwise there will be problems with quota 
calculation as well as other potential random failures. Note that if the 
filename doesn’t contain the ,S= before compression, adding it afterwards 
changes the base filename and thus the message UID. The safest thing to do is 
simply to not compress such files.

Further down on the same page is this:

If the file does exist, rename() (mv) the compressed file over the original 
file.
• Dovecot can now read the file, but to avoid compressing it again on 
the next run, you'll probably want to rename it again to include e.g. a "Z" 
flag in the file name to mark that it was compressed (e.g. 
1223212411.M907959P17184.host,S=3271:2,SZ).

These comments seem to contradict each. Or is there a difference between adding 
the size specifier to the filename and adding a Z flag to the end of the file 
name?

--
Peter West
p...@pbw.id.au
And the great throng heard him gladly.



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