pg_resetxlog says file system is read only?

#postgresql freenode channel directed me to write the hackers list

I have backup files. Version I believe is 7.4.

pg server stopped - short log file is pasted at end of this email

PANIC re checkpoint record seems to indicate running pg_resetxlog

Ran pg_restxlog with -n successfully and it appeared to have numbers
to work with. Then

su postgres
crunch-a:/var/log/postgresql$ /usr/lib/postgresql/bin/pg_resetxlog
/mnt/pgdata/postgres/data
The database server was not shut down cleanly.
Resetting the transaction log may cause data to be lost.
If you want to proceed anyway, use -f to force reset.

crunch-a:/var/log/postgresql$ /usr/lib/postgresql/bin/pg_resetxlog -f
/mnt/pgdata/postgres/data
pg_resetxlog: could not open file
"/mnt/pgdata/postgres/data/pg_xlog/000000AF00000003": Read-only file
system

crunch-a:/var/log/postgresql$ ls -l
/mnt/pgdata/postgres/data/pg_xlog/000000AF00000003
ls: /mnt/pgdata/postgres/data/pg_xlog/000000AF00000003: No such file
or directory

Here is the output of pg_resetxlog -n:

pg_control values:

pg_control version number:            72
Catalog version number:               200310211
Current log file ID:                  175
Next log file segment:                2
Latest checkpoint's StartUpID:        60
Latest checkpoint's NextXID:          193187533
Latest checkpoint's NextOID:          17127133
Database block size:                  8192
Blocks per segment of large relation: 131072
Maximum length of identifiers:        64
Maximum number of function arguments: 32
Date/time type storage:               64-bit integers
Maximum length of locale name:        128
LC_COLLATE:                           C
LC_CTYPE:                             C

Disk does not appear to be full:
df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1             35001508   4130476  29093040  13% /
tmpfs                   518252         0    518252   0% /dev/shm
/dev/sdb1             70557052  17567256  49405700  27% /mnt/pgdata
/dev/sdc1              8744304    393792   7906320   5% /mnt/pglogs
65.221.104.253:/bak  344620624 264253272  80022736  77% /mnt/bak


Complete log (its very short) from time where pg server quit running:

2005-08-03 08:38:27 [32119] LOG:  could not create IPv6 socket:
Address family not supported by protocol
2005-08-03 08:38:27 [32127] LOG:  database system was interrupted at
2005-08-03 03:56:54 EDT
2005-08-03 08:38:27 [32127] LOG:  could not open file
"/var/lib/postgres/data/pg_xlog/000000AF00000001" (log file 175,
segment 1): No such file or directory
2005-08-03 08:38:27 [32127] LOG:  invalid primary checkpoint record
2005-08-03 08:38:27 [32127] LOG:  could not open file
"/var/lib/postgres/data/pg_xlog/000000AF00000001" (log file 175,
segment 1): No such file or directory
2005-08-03 08:38:27 [32127] LOG:  invalid secondary checkpoint record
2005-08-03 08:38:27 [32127] PANIC:  could not locate a valid checkpoint record
2005-08-03 08:38:27 [32119] LOG:  startup process (PID 32127) was
terminated by signal 6
2005-08-03 08:38:27 [32119] LOG:  aborting startup due to startup
process failure
2005-08-03 10:08:50 [10168] LOG:  could not create IPv6 socket:
Address family not supported by protocol
2005-08-03 10:08:50 [10173] LOG:  database system was shut down at
2005-08-03 10:05:42 EDT
2005-08-03 10:08:50 [10173] LOG:  could not open file
"/var/lib/postgres/data/pg_xlog/000000AF00000003" (log file 175,
segment 3): No such file or directory
2005-08-03 10:08:50 [10173] LOG:  invalid primary checkpoint record
2005-08-03 10:08:50 [10173] LOG:  invalid secondary checkpoint link in
control file
2005-08-03 10:08:50 [10173] PANIC:  could not locate a valid checkpoint record
2005-08-03 10:08:50 [10168] LOG:  startup process (PID 10173) was
terminated by signal 6
2005-08-03 10:08:50 [10168] LOG:  aborting startup due to startup
process failure