Match User *000
ChrootDirectory /var/backup/000/%u
AuthorizedKeysFile /var/backup/000/%u/%h/.ssh/authorized_keys
Match
Match User *001
ChrootDirectory /var/backup/001/%u
AuthorizedKeysFile /var/backup/001/%u/%h/.ssh/authorized_keys
Match
...
Match User *999
ChrootDirectory /var/backup/999/%u
AuthorizedKeysFile /var/backup/999/%u/%h/.ssh/authorized_keys
Match
</source>
FILE=/etc/ssh/sshd_config;
for ((x=in {0..999} ; x<1000; x+=1)); \do \
printf "Match User *%03d\n" $x >> ${FILE}; \
printf " ChrootDirectory /var/backup/%03d/%%u\n" $x >> ${FILE}; \
printf " AuthorizedKeysFile /var/backup/%03d/%%u/%%h/.ssh/authorized_keys\n" $x >> ${FILE}; \
printf "Match\n" >> ${FILE}; \
done