The opkg utility (an ipkg fork) is a lightweight package manager used to download and install OpenWrt packages from local package repositories or ones located in the Internet.
GNU/Linux users already familiar with apt-get, aptitude, pacman, yum, etc. will recognize the similarities. It also has similarities with NSLU2's Optware, also made for embedded devices. OPKG is however a full package manager for the root file system, instead of just a way to add software to a seperate directory (e.g. /opt). This also includes the possibility to add kernel modules and drivers. OPKG is sometimes called Entware, but this is mainly to refer to the Entware repository for embedded devices.

Opkg attempts to resolve dependencies with packages in the repositories - if this fails, it will report an error, and abort the installation of that package.

Missing dependencies with third-party packages are probably available from the source of the package.
To ignore dependency errors, pass the --force-depends flag.

Please note: If you are using a snapshot / trunk / bleeding edge version, opkg install <pkg> may fail, if the package in the repository is for a newer kernel version than the kernel version on your flash. In this case, you will get the error message "Cannot satisfy the following dependencies for…"
See also OpenWrt FAQ

opkg must have one sub-command argument:
usage: opkg [options...] sub-command [arguments...]
where sub-command is one of:

You can use glob patterns.

To install a package run the following commands. List of available packages is lost upon reboot, so make sure to update the list before trying to install a package

opkg update
opkg install <package>

To search

• opkg list will display only Package name — Version — Description
• opkg info will display all available information.

You can make use of glob patterns directly and also write a little shell script to use Regular expressions and otherwise further process information. Use a pipe (|) and grep or awk or sed to filter that output:

• opkg list | grep pattern
• opkg list | awk '/pattern/ {print $0}
• opkg info kmod-ipt-* | awk '/length/ {print $0}'
• opkg list-installed | awk '{print $1}' | sed ':M;N;$!bM;s#\n# #g'
• var="packagename1 packagename2 packagename2"; for i in $var; do opkg info $i; done;
• opkg depends dropbear doesn't work either.

The only configuration file is /etc/opkg.conf. It could look like this:

src/gz snapshots http://downloads.openwrt.org/snapshots/trunk/ar71xx/packages
dest root /
dest ram /tmp
lists_dir ext /var/opkg-lists
option overlay_root /overlay

You can configure opkg to fetch the packages locally:

src/gz local file:///path/to/packagesDirectory

Barrier_breaker uses multiple repositories, where every repository requires a unique identifier. It is logical to use their original names, e.g.:

...
src/gz base file:///path/to/packages/directory/packages/base
src/gz luci file:///path/to/packages/directory/packages/luci
src/gz packages file:///path/to/packages/directory/packages/packages
src/gz oldpackages file:///path/to/packages/directory/packages/oldpackages
... etc ...

Live example:

r=44685
search="http://downloads.openwrt.org/snapshots/trunk/ar71xx/generic"
replace="file:///mnt/sdcard/shared/users/www/r$r"
sed -i -e "s!$search!$replace!" /etc/opkg.conf

Share for a second router:

ln -s /mnt/sdcard/shared/users/www /www/pendrive

In the second router:

r=44685
search="downloads.openwrt.org/snapshots/trunk/ar71xx/generic"
replace="192.168.1.1/pendrive/r$r"
sed -i -e "s!$search!$replace!" /etc/opkg.conf

By default, opkg only allows packages with the architecture all (= architecture independant) and the architecture of the installed target. In order to source packages from a foreign, but compatible target, the list of allowed architectures can be overrided in opkg.conf with the use of arch options:

arch all 100
arch brcm4716 200
arch brcm47xx 300

This example would allow installing brcm47xx (= family of SoCs) packages on the brcm4716 (a specific SoC) target. The number specifies a priority index which is used by opkg to determine which package to prefer in case it is available in multiple architectures.

To use opkg through a proxy, add the following to /etc/opkg.conf:

option http_proxy http://proxy.example.org:8080/
option ftp_proxy ftp://proxy.example.org:2121/

Use the options below to authenticate against the proxy server:

option proxy_username xxxx
option proxy_password xxxx

The authentication may fail due to the limitations of busybox wget. Try passing the username and password as part of the url in this case.

option http_proxy http://username:password@proxy.example.org:8080/
option ftp_proxy http://username:password@proxy.example.org:2121/

Use extroot and you are done with it. No further configuration is necessary.

One very useful feature of opkg, which may be unfamiliar to those used to tools such as the apt family, is the ability to specify a destination for any package installation.

Many packages are not relocatable and will fail to install cleanly when installed to a non-root location! LuCI for example will fail to find its modules and will not work without manual fixes! Use Extroot instead!
Don't expect this solution to work out-of-the-box, most packages will need additional symlinks or hacks to correctly work under the changed path!

The default opkg.conf actually contains three destinations:

dest root /
dest ram /tmp
dest mnt /mnt

The format of destination lines is simply the keyword dest, followed by a name for this destination (this can be anything), followed by a filesystem location. Any destination that has been thus configured can then be specified on the opkg command line like this:

opkg install somepackage -d destination_name

The dest argument must refer to one of the defined destinations in /etc/opkg.conf, e.g. -d ram to install packages to /tmp/.

If you want to install kernel modules on any other destination than root, you might want to read this first: https://dev.openwrt.org/ticket/10739

First mount an external filesystem, see Mounting Filesystems for help with that. Then edit /etc/opkg.conf:

• Add the line dest usb /opt to the bottom of the file
• Execute the following command (assuming that /mnt/sda1 is the path to the mount point of your external filesystem):

  ln -s /mnt/sda1 /opt

• If you installed packages to tmp folder via opkg -d ram then you need to add new binary and library paths:

  export PATH=$PATH:/tmp/bin:/tmp/sbin:/tmp/usr/bin:/tmp/usr/sbin
  export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/tmp/lib:/tmp/usr/lib

• Edit /etc/profile and add the new mount point to your paths variables:

  export PATH=<current default path>:/opt/bin:/opt/sbin:/opt/usr/bin:/opt/usr/sbin
  export LD_LIBRARY_PATH=<current default LD library path>:/opt/lib:/opt/usr/lib

• From here, you should be able to install new packages to your new mount point as follows:

  opkg update
  opkg -dest usb install asterisk14  # or whatever else you want…

• If you install packages to external filesystems that have a startup script under /etc/init.d and (if enabled) under /etc/rc.d you need to set a sysmlink to /etc/init.d, e.g.:

   ln -s /usb/etc/init.d/openvpn /etc/init.d/openvpn

• Libraries installed along with those packages are also installed to the external filesystem. This causes the programm not to start during bootup. You need to manually set the LD_LIBRARY_PATH in each 'external' startup script:

   export LD_LIBRARY_PATH=/lib:/usr/lib:/tmp/lib:/tmp/usr/lib:/usb/lib:/usb/usr/lib

1. mount external partition, see Mounting Filesystems
2. change /etc/opkg.conf and either add a new destination to desired mount point, or
3. modify dest root to point to your usb drive
4. copy contents of /usr/lib/opkg to your mount point, e.g. USB drive
5. map directories where it is likely that they'll receive lots of files to your usb drive, for example with mount –bind during startup. /etc/rc.local could be one place where to map the directories.

example:

mount --bind /mnt/usb/root /root
mount --bind /mnt/usb/usr/local /usr/local
mount --bind /mnt/usb/home  /home

For packages which contain libraries, and are installed on external drive, those libraries need to be found. Installing ldconfig, and listing the additional library paths in /etc/ld.so.conf will take care of that. ldconfig must be executed after new libraries have been installed, and it can be installed to external drive. Executing it once during boot may be a good idea. Maybe /etc/rc.local.

Kernel modules that are installed to a non-standard location may not be properly automatically inserted into the kernel when required, and manual insertion may be necessary. For example, after installing libdevmapper under /mnt, insert the modules thus:

insmod /mnt/lib/modules/2.6.36.4/dm-mod.ko

You could install daemons and "core" services on the internal flash and install optional packages to external mount point. During boot, the external directories with executables (<mountpoint>/[bin,sbin,usr/bin,usr/sbin] are added to PATH if mount of external drive took place. That way the router continues to provide all relevant services, even with external storage disconnected.

Problems arose with these packages, when installing to external drive:

• file
  It installs its dependency libmagic to external drive too, but looks for that lib on root device.
  Fix: a script with be name "file" in a directory in PATH which is searched before the directory which contains the executable "file", which calls file (full path) with option -m and path to the libmagic:
  

  #!/bin/sh
  /mnt/usb/usr/bin/file -m /mnt/usb/usr/share/file/magic "$@"

  after saving the script, and making it executable (chmod +x /path/of/script/file), executing once "hash -r" may or may not be needed.
• netcat
  Not really a problem, but the link nc (busybox?) was still pointing to a file with wrong location.
  Moving the nc link to external drive (to the dir containing netcat) fixes that.
• nfsd
/etc/init.d/nfsd contains hardcoded paths to executables on /usr/sbin
  Fix: edit /etc/init.d/nfsd, by changing those paths to updated location.

• lvm2
/etc/init.d/lvm2 contains hardcoded paths to executables on /sbin
  Fix: edit /etc/init.d/lvm2, by changing these paths to updated location.

More information on installing and using ldconfig can be found in this article.

Some programs need additional config files to run, and you will have to create soft links between the root filesystem and the external storage one (e.g. USB). As an example, to successfully run Midnight Commander after installing it on a USB stick, you must run:

ln -s $USB/usr/share/terminfo/ /usb/share/
ln -s $USB/etc/mc /etc/mc

If opkg runs out of space, it usually fails to recover cleanly leaving dangling lock files in place resulting in a Could not obtain administrative lock error. The lock file can be deleted by issuing the rm /usr/lib/opkg/lock command.

Additionally, opkg may not remove the files it was installing.
One way to do this is get a list of the files it was installing, then delete them.

Replace the url with the appropriate package.

(cd /; \
 wget -qO- http://downloads.openwrt.org/snapshots/trunk/ar7/packages/6in4_10-1_all.ipk | \
 tar -Oxz ./data.tar.gz | tar -tz | xargs rm)

However, the above line does not delete the dependencies that were installed along with the package responsible. Also, it leaves empty directories around. The script below intends to fix those.

#!/bin/sh
#takes one argument/parameter: the name of the package which didn't install correctly and should be removed along with its dependencies
#example: ./opkgremovepartlyinstalledpackage.sh pulseaudio-daemon

#get list of all packages that would be installed along with package x
PACKAGES=`opkg --force-space --noaction install $1 | grep "http:" | cut -f 2 -d ' ' | sed 's/\.$//'`
opkg update
for i in $PACKAGES
do
        LIST=`wget -qO- $i | tar -Oxz ./data.tar.gz | tar -tz | sort -r | sed 's/^./\/overlay\/upper/'`
        for f in $LIST
        do
                if [ -f $f ]
                then
                        echo "Removing file $f"
                        rm -f $f
                fi
                if [ -d $f ]
                then
                        echo "Try to remove directory $f (will only work on empty directories)"
                        rmdir $f
                fi
        done
done
echo "You may need to reboot for the free space to become visible"

For colorize opkg output, you can use http://pastie.org/5464938.

Find installed packages of a specific install target (eg root, usb)

# ALL
opkg list-installed |sed "s/ - .*//p;d" |xargs -n1 opkg files |sed "s/^Package \(.*\) and has .*/\1/p;d"
# Destination `usb'
opkg list-installed |sed "s/ - .*//p;d" |xargs -n1 opkg files |sed "s/^Package \(.*\) and has .*/\1/p;d" |grep -w usb$

Since Trunk r23173 respectively Backfire r23206 the kernel and kmod packages are flagged as hold. The opkg upgrade command won't attempt to update them anymore.

• packages
• Pacman Rosetta