2004.11_Charly's Column-Synchronizing Mail Accounts with Imapsync.pdf

Charly’s column

SYSADMIN

Mail Mover

If you need to set up a new mail server, use the handy imapsync tool to

migrate the contents of any existing IMAP mailboxes. imapsync synchronizes

the new and old mail servers, preserving mailbox settings so users won’t

notice the change. BY CHARLY KÜHNAST

a mail migration. Unfortunately, per-

fection is rarely the case in

production environments. One problem

is that migration routines tend to reset

read/unread flags, leaving the user with

an inbox where everything is tagged as

“new.” The Perl script imapsync [1]

solves this problem by synchronizing

IMAP accounts between servers.

committing anything to disk. Assuming I

am happy with the results of the simula-

tion, I can run the command without the

--dry option to perform the actual migra-

tion.

The preceding command creates a

security risk by directly passing my pass-

words (0r1and0 and 10nd0n) to

imapsync. A user logged on to the

machine could type ps auxwww and

grab the passwords off the process list. A

better solution is to store my passwords

in a file with restrictive permissions

( chmod 400 filename). I could then use

the following command:

Practicalities

I have a tired old mail server with an IP

address of 10.0.0.5 and a new mail

server with the address 10.0.0.10. My

username on the old machine is charly ,

and my username on the new machine is

ckuehnast . I will begin by simulating a

mail migration using imapsync’s --dry--

option:

Incidentally, the author of imapsync

also has another useful tool called

Pop2imap [2]. Pop2imap migrates POP3

accounts to IMAP servers. According to

the official description of the tool,

“Pop2imap is a tool for incremental POP

to IMAP transfer from one mailbox to

another.” Like imapsync, Pop2imap

reduces the amount of data transferred

across the network by only copying mes-

sages that are not present on both

servers. If you are accustomed to run-

ning imapsync, you should have no

trouble at all migrating your POP3

accounts using Pop2imap.

imapsync --dry --host1 10.0.0.5 U

--user1 charly --passfile1 U

/etc/charly-pass --host2 U

10.0.0.10 --user2 ckuehnast U

--passfile2 /etc/ckuehnast-pass

imapsync --dry --host1 10.0.0.5 U

--user1 charly --password1 U

0r1and0 -- host2 10.0.0.10 U

--user2 ckuehnast --password2 U

10nd0n

Unfortunately, imapsync must still trans-

mit the password as clear text in order to

log on to the target server. imapsync

does not support IMAP via SSL, and this

puts admins at a disadvantage against

sniffers.

■

INFO

The --dry option tells imapsync to exe-

cutes all the steps without actually

[1] imapsync: http://www.linux-france.org/

prj/imapsync/

[2] Pop2imap: http://www.linux-france.org/

prj/pop2imap/

Clever Boy

imapsync does not simply transfer the

whole IMAP account. Instead, it inspects

the target server to see if any mail is in

the account. If so, imapsync performs a

differential migration to synchronize the

accounts. If an interruption occurs dur-

ing the transfer, the tool simply restarts

and picks up from where it left off.

If you are sure you will not need the

messages on the old server in future, you

can pass the --delete parameter to imap-

sync. --delete removes the messages from

the source server after the migration.

SYSADMIN

Admin Workshop ................... 58

A good place to start with troubleshooting

is the system process list. This month we

look at the processes running on a typical

Linux workstation soon after startup.

PHP Security ............................ 62

PHP is safer than an ordinary CGI script, but

safer may not be safe enough. We’ll show

you how to build security into your PHP-

based Web pages.

Charly Kühnast is a

Unix System Manager

at the data- center in

Moers, near

Germany’s famous

River Rhine. His tasks

include ensuring fire-

wall security and availability and

taking care of the DMZ (demilitarized

zone).

www.linux-magazine.com November 2004

The Sysadmin’s Daily Grind: imapsync

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