Problem about initdb

After many trials, I do not yet understand the problem that occurs me
when I execute "initdb -l /usr/lib/pgsql -r post -d" on my system.
I report the output below:

Running with debug mode on.
initdb: using /usr/lib/pgsql/local1_template1.bki.source as input to
create the template database.
initdb: using /usr/lib/pgsql/global1.bki.source as input to create the
global classes.
initdb: using /usr/lib/pgsql/pg_hba.conf.sample as the host-based
authentication control file.

We are initializing the database system with username costa (uid=10103).
This user will own all the files and must also own the server process.

Creating template database in post/base/template1
Running: postgres -boot -C -F -Dpost -d template1
<proname name>
<proowner int4>
<prolang oid>
<proisinh bool>
<proistrusted bool>
<proiscachable bool>
<pronargs int2>
<proretset bool>
<prorettype oid>
<proargtypes oid8>
<probyte_pct int4>
<properbyte_cpu int4>
<propercall_cpu int4>
<prooutin_ratio int4>
<prosrc text>
<probin bytea>

> creating bootstrap relation
bootstrap relation created ok
> Commit End
tuple 1242<Inserting value: 'boolin'
Typ == NULL, typeindex = 3 idx = 0
boolin End InsertValue
Inserting value: '10103'
Typ == NULL, typeindex = 7 idx = 1
10103 End InsertValue
Inserting value: '11'
Typ == NULL, typeindex = 10 idx = 2
11 End InsertValue
Inserting value: 'f'
Typ == NULL, typeindex = 0 idx = 3
f End InsertValue
Inserting value: 't'
Typ == NULL, typeindex = 0 idx = 4
t End InsertValue
Inserting value: 'f'
Typ == NULL, typeindex = 0 idx = 5
f End InsertValue
Inserting value: '1'
Typ == NULL, typeindex = 5 idx = 6
1 End InsertValue
Inserting value: 'f'
Typ == NULL, typeindex = 0 idx = 7
f End InsertValue
Inserting value: '16'
Typ == NULL, typeindex = 10 idx = 8
16 End InsertValue
Inserting value: '0'
Typ == NULL, typeindex = 14 idx = 9
0 0 0 0 0 0 0 0 End InsertValue
Inserting value: '100'
Typ == NULL, typeindex = 7 idx = 10
100 End InsertValue
Inserting value: '0'
Typ == NULL, typeindex = 7 idx = 11
0 End InsertValue
Inserting value: '0'
Typ == NULL, typeindex = 7 idx = 12
0 End InsertValue
Inserting value: '100'
Typ == NULL, typeindex = 7 idx = 13
100 End InsertValue
Inserting value: 'foo'
Typ == NULL, typeindex = 9 idx = 14
foo End InsertValue
Inserting value: 'bar'
Typ == NULL, typeindex = 1 idx = 15
bar End InsertValue
Insert Begin
InsertOneTuple oid 1242, 16 attrs
ERROR:  cannot read block 0 of pg_variable
ERROR:  cannot read block 0 of pg_variable
initdb: could not create template database
initdb: cleaning up by wiping out post/base/template1


I hope that someone can help me.
Thanks.

Roberto Costa (costa@ensta.fr)