Linux: Gentoo Cheat Sheet

By: B Macomber

cat /var/lib/portage/world
	to show packages explicitly installed.
equery list *
	to show all the installed packages, including dependencies.
less /usr/portage/profiles/use.desc
	to view descriptions of the common USE flags.
nano /etc/portage/make.conf
	to specify USE flags.
nano /etc/portage/package.use
	to specify USE flags for individual packages.
emerge --sync
	to get the latest Portage tree (metadata about packages), which is needed for all subsequent emerge commands.
eselect news read
	to read news about Portage updates.
emerge -s package
	to search for a package to see what exists.
emerge -S package
	like above, except it will search all the descriptive text in addition to the package name. Note that Regular Expressions are used for this search. equery uses package
	to see the effect of USE flags on the specified package (requires gentoolkit).
emerge -p package
	to pretend to install a package, in order to show a preview of the dependencies, etc. that will be installed in total.
emerge -a package
	like above, except it will ask to proceed after showing a preview of what will happen.
emerge -q package
	to install quietly, omitting all the technical compilation output.
emerge -uD --with-bdeps=y @world -p
	to update all packages explicitly installed, as well as their dependencies and their build dependencies, pretending at first.
emerge -uDN --with-bdeps=y @world -p
	like above, except changes to USE flags will also be considered in determining what needs to be re-built.
etc-update
	to resolve changes to config files made by Portage updates.
eread
	to view Portage logs.
less /var/log/portage/elog/summary.log
	ditto.
eselect
	to choose which SLOT of a package to use (among other things).
gcc-config
	to choose which version of C++ compiler to use.
env-update && source /etc/profile && emerge binutils glibc -1q
	to rebuild the "toolchain" after changing which version of C++ compiler to use.
emerge -Ca package
	to remove a package.
emerge -ca (--depclean --ask)
	to remove unneeded dependencies.
emerge @preserved-rebuild
	to rebuild packages using outdated libraries.
revdep-rebuild -p
	to rebuild packages whose (dynamically linked) dependencies are no longer needed and have been removed (requires gentoolkit), pretending at first.
eclean -d -p distfiles
	to delete leftover package installation/build files; destructive means to remove stuff except for packages explicitly installed, pretending at first.
rm /usr/portage/distfiles/*
	to delete leftover package installation/build files, regardless of whether you might want them again.
eselect kernel
	to choose a version of the kernel source.
cd /usr/src/linux && make menuconfig
	to configure kernel.
cd /usr/src/linux && make oldconfig
	to configure kernel, showing only options that have changed since the current .config file. Since this will only prompt you with a sequence of questions, you may want to run the above command at the same time in another terminal so that you can browse through the questions and gain some context of what's being asked.
make && make modules_install
	to build kernel & modules.
mount /boot && cp arch/x86_64/boot/bzImage /boot/kernel-x.x.x-hardened && nano /etc/lilo.conf && lilo && umount /boot
	to install kernel; change "x.x.x-hardened" to whatever version you're building.
rm -r /usr/src/linux-x.x.x-hardened && rm -r /lib/modules/x.x.x-hardened && rm /boot/kernel-x.x.x-hardened
	to remove an old, obsolete kernel that's no longer acknowledged by Portage.
rc-config list
	to show which services are started in which runlevels, including those inactive.
rc-update
	to show which services are started in which runlevels, in a slightly different format.
rc-update add service runlevel
	to add a service, such as apache2, to a runlevel, such as default, so that it gets started when the computer boots up.
rc-status
	to show which services are currently running.
/etc/init.d/service restart
	to restart a service. Besides restart, you can also start, stop, etc.
ntpq -p
	to query the status of your Network Time Protocol Daemon.
nohup command > /dev/null 2>&1 &
	to run a process in the background, squelching its output, continuing even after you log off.
echo 1 > /proc/sys/kernel/sysrq && echo b > /proc/sysrq-trigger
	to remotely reboot without accessing any disks, when all else fails.
head -c 200 /dev/urandom | LC_CTYPE=C tr -c -d '[:alnum:]' | head -c 10
	to generate a password of 10 alphanumeric characters.

By: B Macomber