How to setup SWAP on ddwrt router

By default there is no SWAP on the ddwrt routers, in case you need it you have to setup it on your own, but that is not so complicated, just read the documentations.

Source documentation:
http://www.dd-wrt.com/wiki/index.php/Linux_SWAP#Requirements

Here is what I have done:

1. Create a file for the swap

root@mygateway:/# dd if=/dev/zero of=/mnt/myswap.swp bs=1k count=80000 80000+0 records in 80000+0 records out

2. Install busybox (optional, it is already installed)

root@mygateway:/# ipkg-opt install busybox Installing busybox (1.10.3-1) to /opt/… Downloading http://ipkg.nslu2-linux.org/feeds/optware/ddwrt/cross/stable/busybox_1.10.3-1_mipsel.ipk Installing busybox-base (1.10.3-1) to /opt/… Downloading http://ipkg.nslu2-linux.org/feeds/optware/ddwrt/cross/stable/busybox-base_1.10.3-1_mipsel.ipk Installing busybox-links (1.10.3-1) to /opt/… Downloading http://ipkg.nslu2-linux.org/feeds/optware/ddwrt/cross/stable/busybox-links_1.10.3-1_mipsel.ipk Configuring busybox Configuring busybox-base Configuring busybox-links update-alternatives: Linking //opt/bin/[ to /opt/bin/busybox update-alternatives: Linking //opt/bin/[[ to /opt/bin/busybox update-alternatives: Linking //opt/bin/arping to /opt/bin/busybox update-alternatives: Linking //opt/bin/ash to /opt/bin/busybox update-alternatives: Linking //opt/bin/awk to /opt/bin/busybox update-alternatives: Linking //opt/bin/basename to /opt/bin/busybox update-alternatives: Linking //opt/bin/bunzip2 to /opt/bin/busybox update-alternatives: Linking //opt/bin/bzcat to /opt/bin/busybox update-alternatives: Linking //opt/bin/bzip2 to /opt/bin/busybox update-alternatives: Linking //opt/bin/cal to /opt/bin/busybox update-alternatives: Linking //opt/bin/cat to /opt/bin/busybox update-alternatives: Linking //opt/bin/chattr to /opt/bin/busybox update-alternatives: Linking //opt/bin/chgrp to /opt/bin/busybox update-alternatives: Linking //opt/bin/chmod to /opt/bin/busybox update-alternatives: Linking //opt/bin/chown to /opt/bin/busybox update-alternatives: Linking //opt/bin/chroot to /opt/bin/busybox update-alternatives: Linking //opt/bin/chrt to /opt/bin/busybox update-alternatives: Linking //opt/bin/chvt to /opt/bin/busybox update-alternatives: Linking //opt/bin/cksum to /opt/bin/busybox update-alternatives: Linking //opt/bin/clear to /opt/bin/busybox update-alternatives: Linking //opt/bin/cmp to /opt/bin/busybox update-alternatives: Linking //opt/bin/comm to /opt/bin/busybox update-alternatives: Linking //opt/bin/cp to /opt/bin/busybox update-alternatives: Linking //opt/bin/cpio to /opt/bin/busybox update-alternatives: Linking //opt/bin/cut to /opt/bin/busybox update-alternatives: Linking //opt/bin/date to /opt/bin/busybox update-alternatives: Linking //opt/bin/dd to /opt/bin/busybox update-alternatives: Linking //opt/bin/deallocvt to /opt/bin/busybox update-alternatives: Linking //opt/bin/df to /opt/bin/busybox update-alternatives: Linking //opt/bin/diff to /opt/bin/busybox update-alternatives: Linking //opt/bin/dirname to /opt/bin/busybox update-alternatives: Linking //opt/bin/dmesg to /opt/bin/busybox update-alternatives: Linking //opt/bin/dos2unix to /opt/bin/busybox update-alternatives: Linking //opt/bin/du to /opt/bin/busybox update-alternatives: Linking //opt/bin/echo to /opt/bin/busybox update-alternatives: Linking //opt/bin/ed to /opt/bin/busybox update-alternatives: Linking //opt/bin/egrep to /opt/bin/busybox update-alternatives: Linking //opt/bin/eject to /opt/bin/busybox update-alternatives: Linking //opt/bin/env to /opt/bin/busybox update-alternatives: Linking //opt/bin/ether-wake to /opt/bin/busybox update-alternatives: Linking //opt/bin/expr to /opt/bin/busybox update-alternatives: Linking //opt/bin/false to /opt/bin/busybox update-alternatives: Linking //opt/bin/fgrep to /opt/bin/busybox update-alternatives: Linking //opt/bin/find to /opt/bin/busybox update-alternatives: Linking //opt/bin/free to /opt/bin/busybox update-alternatives: Linking //opt/bin/grep to /opt/bin/busybox update-alternatives: Linking //opt/bin/gunzip to /opt/bin/busybox update-alternatives: Linking //opt/bin/gzip to /opt/bin/busybox update-alternatives: Linking //opt/bin/head to /opt/bin/busybox update-alternatives: Linking //opt/bin/hexdump to /opt/bin/busybox update-alternatives: Linking //opt/bin/hostname to /opt/bin/busybox update-alternatives: Linking //opt/bin/id to /opt/bin/busybox update-alternatives: Linking //opt/bin/ifconfig to /opt/bin/busybox update-alternatives: Linking //opt/bin/install to /opt/bin/busybox update-alternatives: Linking //opt/bin/ip to /opt/bin/busybox update-alternatives: Linking //opt/bin/ipcrm to /opt/bin/busybox update-alternatives: Linking //opt/bin/ipcs to /opt/bin/busybox update-alternatives: Linking //opt/bin/kill to /opt/bin/busybox update-alternatives: Linking //opt/bin/killall to /opt/bin/busybox update-alternatives: Linking //opt/bin/killall5 to /opt/bin/busybox update-alternatives: Linking //opt/bin/less to /opt/bin/busybox update-alternatives: Linking //opt/bin/ln to /opt/bin/busybox update-alternatives: Linking //opt/bin/logger to /opt/bin/busybox update-alternatives: Linking //opt/bin/logname to /opt/bin/busybox update-alternatives: Linking //opt/bin/ls to /opt/bin/busybox update-alternatives: Linking //opt/bin/lsattr to /opt/bin/busybox update-alternatives: Linking //opt/bin/md5sum to /opt/bin/busybox update-alternatives: Linking //opt/bin/mkdir to /opt/bin/busybox update-alternatives: Linking //opt/bin/mkfifo to /opt/bin/busybox update-alternatives: Linking //opt/bin/mknod to /opt/bin/busybox update-alternatives: Linking //opt/bin/mount to /opt/bin/busybox update-alternatives: Linking //opt/bin/mv to /opt/bin/busybox update-alternatives: Linking //opt/bin/nc to /opt/bin/busybox update-alternatives: Linking //opt/bin/netstat to /opt/bin/busybox update-alternatives: Linking //opt/bin/nice to /opt/bin/busybox update-alternatives: Linking //opt/bin/nmeter to /opt/bin/busybox update-alternatives: Linking //opt/bin/nohup to /opt/bin/busybox update-alternatives: Linking //opt/bin/od to /opt/bin/busybox update-alternatives: Linking //opt/bin/openvt to /opt/bin/busybox update-alternatives: Linking //opt/bin/patch to /opt/bin/busybox update-alternatives: Linking //opt/bin/pidof to /opt/bin/busybox update-alternatives: Linking //opt/bin/ping to /opt/bin/busybox update-alternatives: Linking //opt/bin/ping6 to /opt/bin/busybox update-alternatives: Linking //opt/bin/printf to /opt/bin/busybox update-alternatives: Linking //opt/bin/ps to /opt/bin/busybox update-alternatives: Linking //opt/bin/pwd to /opt/bin/busybox update-alternatives: Linking //opt/bin/readlink to /opt/bin/busybox update-alternatives: Linking //opt/bin/realpath to /opt/bin/busybox update-alternatives: Linking //opt/bin/renice to /opt/bin/busybox update-alternatives: Linking //opt/bin/reset to /opt/bin/busybox update-alternatives: Linking //opt/bin/resize to /opt/bin/busybox update-alternatives: Linking //opt/bin/rm to /opt/bin/busybox update-alternatives: Linking //opt/bin/rmdir to /opt/bin/busybox update-alternatives: Linking //opt/bin/script to /opt/bin/busybox update-alternatives: Linking //opt/bin/sed to /opt/bin/busybox update-alternatives: Linking //opt/bin/seq to /opt/bin/busybox update-alternatives: Linking //opt/bin/sh to /opt/bin/busybox update-alternatives: Linking //opt/bin/sha1sum to /opt/bin/busybox update-alternatives: Linking //opt/bin/sleep to /opt/bin/busybox update-alternatives: Linking //opt/bin/sort to /opt/bin/busybox update-alternatives: Linking //opt/bin/stat to /opt/bin/busybox update-alternatives: Linking //opt/bin/strings to /opt/bin/busybox update-alternatives: Linking //opt/bin/stty to /opt/bin/busybox update-alternatives: Linking //opt/bin/sync to /opt/bin/busybox update-alternatives: Linking //opt/bin/tail to /opt/bin/busybox update-alternatives: Linking //opt/bin/tar to /opt/bin/busybox update-alternatives: Linking //opt/bin/tee to /opt/bin/busybox update-alternatives: Linking //opt/bin/test to /opt/bin/busybox update-alternatives: Linking //opt/bin/time to /opt/bin/busybox update-alternatives: Linking //opt/bin/top to /opt/bin/busybox update-alternatives: Linking //opt/bin/touch to /opt/bin/busybox update-alternatives: Linking //opt/bin/tr to /opt/bin/busybox update-alternatives: Linking //opt/bin/true to /opt/bin/busybox update-alternatives: Linking //opt/bin/tty to /opt/bin/busybox update-alternatives: Linking //opt/bin/umount to /opt/bin/busybox update-alternatives: Linking //opt/bin/uname to /opt/bin/busybox update-alternatives: Linking //opt/bin/uncompress to /opt/bin/busybox update-alternatives: Linking //opt/bin/uniq to /opt/bin/busybox update-alternatives: Linking //opt/bin/unix2dos to /opt/bin/busybox update-alternatives: Linking //opt/bin/unzip to /opt/bin/busybox update-alternatives: Linking //opt/bin/uptime to /opt/bin/busybox update-alternatives: Linking //opt/bin/usleep to /opt/bin/busybox update-alternatives: Linking //opt/bin/uudecode to /opt/bin/busybox update-alternatives: Linking //opt/bin/uuencode to /opt/bin/busybox update-alternatives: Linking //opt/bin/vi to /opt/bin/busybox update-alternatives: Linking //opt/bin/watch to /opt/bin/busybox update-alternatives: Linking //opt/bin/wc to /opt/bin/busybox update-alternatives: Linking //opt/bin/which to /opt/bin/busybox update-alternatives: Linking //opt/bin/who to /opt/bin/busybox update-alternatives: Linking //opt/bin/whoami to /opt/bin/busybox update-alternatives: Linking //opt/bin/xargs to /opt/bin/busybox update-alternatives: Linking //opt/bin/yes to /opt/bin/busybox update-alternatives: Linking //opt/bin/zcat to /opt/bin/busybox update-alternatives: Linking //opt/libexec/syslogd to /opt/bin/busybox update-alternatives: Linking //opt/sbin/arp to /opt/bin/busybox update-alternatives: Linking //opt/sbin/fdisk to /opt/bin/busybox update-alternatives: Linking //opt/sbin/fsck to /opt/bin/busybox update-alternatives: Linking //opt/sbin/hdparm to /opt/bin/busybox update-alternatives: Linking //opt/sbin/httpd to /opt/bin/busybox update-alternatives: Linking //opt/sbin/hwclock to /opt/bin/busybox update-alternatives: Linking //opt/sbin/insmod to /opt/bin/busybox update-alternatives: Linking //opt/sbin/klogd to /opt/bin/busybox update-alternatives: Linking //opt/sbin/losetup to /opt/bin/busybox update-alternatives: Linking //opt/sbin/lsmod to /opt/bin/busybox update-alternatives: Linking //opt/sbin/mkswap to /opt/bin/busybox update-alternatives: Linking //opt/sbin/modprobe to /opt/bin/busybox update-alternatives: Linking //opt/sbin/pivot_root to /opt/bin/busybox update-alternatives: Linking //opt/sbin/rdate to /opt/bin/busybox update-alternatives: Linking //opt/sbin/rmmod to /opt/bin/busybox update-alternatives: Linking //opt/sbin/route to /opt/bin/busybox update-alternatives: Linking //opt/sbin/start-stop-daemon to /opt/bin/busybox update-alternatives: Linking //opt/sbin/swapoff to /opt/bin/busybox update-alternatives: Linking //opt/sbin/swapon to /opt/bin/busybox update-alternatives: Linking //opt/sbin/sysctl to /opt/bin/busybox Successfully terminated.

3. Set up a Linux Swap area

root@mygateway:/# /opt/bin/busybox mkswap /mnt/myswap.swp Setting up swapspace version 1, size = 81915904 bytes root@mygateway:/# root@mygateway:/# /opt/bin/busybox swapon /mnt/myswap.swp root@mygateway:/#

4. Lets check if we see it with free command:

root@mygateway:/# free total used free shared buffers Mem: 58656 50540 8116 0 856 Swap: 79992 0 79992 Total: 138648 50540 88108 root@mygateway:/#

Okay, its there. After starting a couple of snort and tcpdump and a torrent download, the router started to use the swap:

root@mygateway:/tmp/mnt# free total used free shared buffers Mem: 58656 53064 5592 0 92 Swap: 79992 3380 76612 Total: 138648 56444 82204