pg_dumpall: could not connect to database: FATAL

good morning Expert DBAs,
I created a script to do backup and I have faced the error of 

Performing globals backup:pg_dumpall: could not connect to database "template1":FATAL: Ident authentication failed for user "postgres" fro globals backup.  As same as performing schema-only backups and full backup.
Performing schema-only backup:psql:FATAL: Ident authentication failed for user "postgres"the following databases were matched for schema-only backup:
performing full backup:psql:FATAL: Ident authentication failed for user "postgres"

I can run pg_dumpall > postgresdump.sql as postgres user os but couldn't run from script even the script declared BACKUP_USER=postgres

If I take the syntax, -h "$HOSTNAME" -U "$USERNAME" out and the backup script working fine 
# vi pg_backup.config##############################
## POSTGRESQL BACKUP CONFIG ##
##############################
 
# Optional system user to run backups as. If the user the script is running as doesn't match this
# the script terminates. Leave blank to skip check.
BACKUP_USER=
 
# Optional hostname to adhere to pg_hba policies. Will default to "localhost" if none specified.
HOSTNAME="hostname"
 
# Optional username to connect to database as. Will default to "postgres" if none specified.
USERNAME="postgres"
 
# This dir will be created if it doesn't exist. This must be writable by the user the script is
# running as.
BACKUP_DIR=/home/backups/database/postgresql/
 
# List of strings to match against in database name, separated by space or comma, for which we only
# wish to keep a backup of the schema, not the data. Any database names which contain any of these
# values will be considered candidates. (e.g. "system_log" will match "dev_system_log_2010-01")
SCHEMA_ONLY_LIST=""
 
# Will produce a custom-format backup if set to "yes"
ENABLE_CUSTOM_BACKUPS=yes
 
# Will produce a gzipped plain-format backup if set to "yes"
ENABLE_PLAIN_BACKUPS=yes
 
# Will produce gzipped sql file containing the cluster globals, like users and passwords, if set to "yes"
ENABLE_GLOBALS_BACKUPS=yes
 
 
#### SETTINGS FOR ROTATED BACKUPS ####
 
# Which day to take the weekly backup from (1-7 = Monday-Sunday)
DAY_OF_WEEK_TO_KEEP=5
 
# Number of days to keep daily backups
DAYS_TO_KEEP=7
 
# How many weeks to keep weekly backups
WEEKS_TO_KEEP=5
 
######################################
#vi pg_backup.sh#!/bin/bash###########################
####### LOAD CONFIG #######
###########################
 
while [ $# -gt 0 ]; do
case $1 in
-c)
if [ -r "$2" ]; then
source "$2"
shift 2
else
${ECHO} "Unreadable config file \"$2\"" 1>&2
exit 1
fi
;;
*)
${ECHO} "Unknown Option \"$1\"" 1>&2
exit 2
;;
esac
done
 
if [ $# = 0 ]; then
SCRIPTPATH=$(cd ${0%/*} && pwd -P)
source $SCRIPTPATH/pg_backup.config
fi;
 
###########################
#### PRE-BACKUP CHECKS ####
###########################
 
# Make sure we're running as the required backup user
if [ "$BACKUP_USER" != "" -a "$(id -un)" != "$BACKUP_USER" ]; then
echo "This script must be run as $BACKUP_USER. Exiting." 1>&2
exit 1;
fi;
 
 
###########################
### INITIALISE DEFAULTS ###
###########################
 
if [ ! $HOSTNAME ]; then
HOSTNAME="localhost"
fi;
 
if [ ! $USERNAME ]; then
USERNAME="postgres"
fi;
 
 
###########################
#### START THE BACKUPS ####
###########################
 
 
FINAL_BACKUP_DIR=$BACKUP_DIR"`date +\%Y-\%m-\%d`/"
 
echo "Making backup directory in $FINAL_BACKUP_DIR"
 
if ! mkdir -p $FINAL_BACKUP_DIR; then
echo "Cannot create backup directory in $FINAL_BACKUP_DIR. Go and fix it!" 1>&2
exit 1;
fi;
 
 
#######################
### GLOBALS BACKUPS ###
#######################
 
echo -e "\n\nPerforming globals backup"
echo -e "--------------------------------------------\n"
 
if [ $ENABLE_GLOBALS_BACKUPS = "yes" ]
then
echo "Globals backup"
 
if ! pg_dumpall -g -h "$HOSTNAME" -U "$USERNAME" | gzip > $FINAL_BACKUP_DIR"globals".sql.gz.in_progress; then
echo "[!!ERROR!!] Failed to produce globals backup" 1>&2
else
mv $FINAL_BACKUP_DIR"globals".sql.gz.in_progress $FINAL_BACKUP_DIR"globals".sql.gz
fi
else
echo "None"
fi
 
 
###########################
### SCHEMA-ONLY BACKUPS ###
###########################
 
for SCHEMA_ONLY_DB in ${SCHEMA_ONLY_LIST//,/ }
do
SCHEMA_ONLY_CLAUSE="$SCHEMA_ONLY_CLAUSE or datname ~ '$SCHEMA_ONLY_DB'"
done
 
SCHEMA_ONLY_QUERY="select datname from pg_database where false $SCHEMA_ONLY_CLAUSE order by datname;"
 
echo -e "\n\nPerforming schema-only backups"
echo -e "--------------------------------------------\n"
 
SCHEMA_ONLY_DB_LIST=`psql -h "$HOSTNAME" -U "$USERNAME" -At -c "$SCHEMA_ONLY_QUERY" postgres`
 
echo -e "The following databases were matched for schema-only backup:\n${SCHEMA_ONLY_DB_LIST}\n"
 
for DATABASE in $SCHEMA_ONLY_DB_LIST
do
echo "Schema-only backup of $DATABASE"
 
if ! pg_dump -Fp -s -h "$HOSTNAME" -U "$USERNAME" "$DATABASE" | gzip > $FINAL_BACKUP_DIR"$DATABASE"_SCHEMA.sql.gz.in_progress; then
echo "[!!ERROR!!] Failed to backup database schema of $DATABASE" 1>&2
else
mv $FINAL_BACKUP_DIR"$DATABASE"_SCHEMA.sql.gz.in_progress $FINAL_BACKUP_DIR"$DATABASE"_SCHEMA.sql.gz
fi
done
 
 
###########################
###### FULL BACKUPS #######
###########################
 
for SCHEMA_ONLY_DB in ${SCHEMA_ONLY_LIST//,/ }
do
EXCLUDE_SCHEMA_ONLY_CLAUSE="$EXCLUDE_SCHEMA_ONLY_CLAUSE and datname !~ '$SCHEMA_ONLY_DB'"
done
 
FULL_BACKUP_QUERY="select datname from pg_database where not datistemplate and datallowconn $EXCLUDE_SCHEMA_ONLY_CLAUSE order by datname;"
 
echo -e "\n\nPerforming full backups"
echo -e "--------------------------------------------\n"
 
for DATABASE in `psql -h "$HOSTNAME" -U "$USERNAME" -At -c "$FULL_BACKUP_QUERY" postgres`
do
if [ $ENABLE_PLAIN_BACKUPS = "yes" ]
then
echo "Plain backup of $DATABASE"
 
if ! pg_dump -Fp -h "$HOSTNAME" -U "$USERNAME" "$DATABASE" | gzip > $FINAL_BACKUP_DIR"$DATABASE".sql.gz.in_progress; then
echo "[!!ERROR!!] Failed to produce plain backup database $DATABASE" 1>&2
else
mv $FINAL_BACKUP_DIR"$DATABASE".sql.gz.in_progress $FINAL_BACKUP_DIR"$DATABASE".sql.gz
fi
fi
 
if [ $ENABLE_CUSTOM_BACKUPS = "yes" ]
then
echo "Custom backup of $DATABASE"
 
if ! pg_dump -Fc -h "$HOSTNAME" -U "$USERNAME" "$DATABASE" -f $FINAL_BACKUP_DIR"$DATABASE".custom.in_progress; then
echo "[!!ERROR!!] Failed to produce custom backup database $DATABASE" 1>&2
else
mv $FINAL_BACKUP_DIR"$DATABASE".custom.in_progress $FINAL_BACKUP_DIR"$DATABASE".custom
fi
fi
 
done
 
echo -e "\nAll database backups complete!"
I'm appreciate if anyone know how to correct this?
thank you.
v/r, Bach-Nga

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