Netns different outgoing source ip address

7 07 2017

Using three network interfaces, assign each one a different address as source ip address for outgoing traffic:

ip netns add blue
ip link set eth1 netns blue
ip netns add green
ip link set eth2 netns green
ip netns exec blue dhclient eth1
ip netns exec green dhclient eth2
echo "IP eth0: "
echo "IP eth1: "
ip netns exec blue curl
echo "IP eth2: "
ip netns exec green curl


Boot Debian system with EFI Stub kernel

31 08 2016

I try to explain the process of install a Debian system with UEFI and use the EFI Stub property for load the kernel and the ram disk directly from the EFI system firmware, leaving aside “grub-efi” and scratching some seconds at boot time.

– Be sure that UEFI is enabled in your system booting firmware.

– Install Debian following the normal way until the partitioning step.

– UEFI require the following partitioning points:

* Around "500MB" of space
* Bootable flag on
* Partition type "EFI System Partition"

You can select automatic partitioning, and the Debian Installation process will create it automatically or doing the partitioning by hand using the indicated values.

Don’t create this partition under software RAID or LVM, the UEFI won’t read the files under that.

– End with the installation and reboot. If it went correctly, you have a polish running system, booted with grub-uefi, with the UEFI partition mounted under /boot/efi:

/dev/sda1 on /boot/efi type vfat (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=utf8,shortname=mixed,errors=remount-ro)

– Now is time to change the boot process into a EFI Stub, copy the kernel and the ram disk into the UEFI partition:

# cp /vmlinuz /initrd.img /boot/efi/EFI/debian/

– Look for your root filesystem UUID (in this example is sda2, the place were the linux is installed):

# blkid /dev/sda2
/dev/sda2: UUID="955548bd-9c77-4893-8633-3a5e7966dfc9" TYPE="ext4" PARTUUID="4cd59271-18a2-4d00-a65a-a106ee030a1a"

– And create an entry into the UEFI firmware for the linux EFIStub (replace the UUID number with your particular reference):

# efibootmgr -c -g -L "Debian (EFI stub)" -l '\EFI\debian\vmlinuz' -u "root=UUID=955548bd-9c77-4893-8633-3a5e7966dfc9 ro quiet rootfstype=ext4 add_efi_memmap initrd=\\EFI\\debian\\initrd.img"

– Check the UEFI information, the new entry is at the bottom:

# efibootmgr -v
BootCurrent: 0004
BootOrder: 0005,0004,0000,0001,0002,0003
Boot0000* EFI Virtual disk (0.0)
Boot0001* EFI VMware Virtual IDE CDROM Drive (IDE 1:0)
Boot0002* EFI Network
Boot0003* EFI Internal Shell (Unsupported option)
Boot0004* debian
Boot0005* Debian (EFI stub)
root@uefi:/boot/efi/EFI/debian# efibootmgr -v
BootCurrent: 0004
BootOrder: 0005,0004,0000,0001,0002,0003
Boot0000* EFI Virtual disk (0.0) ACPI(a0341d0,0)PCI(15,0)PCI(0,0)SCSI(0,0)
Boot0001* EFI VMware Virtual IDE CDROM Drive (IDE 1:0) ACPI(a0341d0,0)PCI(7,1)ATAPI(1,0,0)
Boot0002* EFI Network ACPI(a0341d0,0)PCI(16,0)PCI(0,0)MAC(MAC(005056948a0a,1)
Boot0003* EFI Internal Shell (Unsupported option) MM(b,e1a3000,e42ffff)FvFile(c57ad6b7-0515-40a8-9d21-551652854e37)
Boot0004* debian HD(1,800,ee000,4f3b579c-10cb-44ca-b845-475b2409eaf7)File(\EFI\debian\grubx64.efi)
Boot0005* Debian (EFI stub) HD(1,800,ee000,4f3b579c-10cb-44ca-b845-475b2409eaf7)File(\EFI\debian\vmlinuz)r.o.o.t.=.U.U.I.D.=. .r.o. .q.u.i.e.t. .r.o.o.t.f.s.t.y.p.e.=.e.x.t.4. .a.d.d._.e.f.i._.m.e.m.m.a.p. .i.n.i.t.r.d.=.\.E.F.I.\.d.e.b.i.a.n.\.i.n.i.t.r.d...i.m.g.
Boot0007* Debian HD(1,800,ee000,4f3b579c-10cb-44ca-b845-475b2409eaf7)File(\EFI\debian\grubx64.efi

– Look close to the information reported, the BootOrder have the new entry listed first, in the next boot the system will take it:

BootCurrent: 0004
BootOrder: 0005,0004,0000,0001,0002,0003

– Now, reboot and check the BootCurrent again:

BootCurrent: 0005
BootOrder: 0005,0004,0000,0001,0002,0003

– Basically it’s done. But for update the kernel and the ram disk automatically when an upgraded is installed, or removed, create the following files and make them executable:

# cat > /etc/kernel/postinst.d/zz-update-efistub << EOF
echo "Updating EFI boot files..."
cp /vmlinuz /initrd.img /boot/efi/EFI/debian/

# chmod +x /etc/kernel/postinst.d/zz-update-efistub# cp /etc/kernel/postinst.d/zz-update-efistub /etc/kernel/postrm.d/zz-update-efistub

As a note, is it possible to substitute this script with systemd units. Look into the Arch linux wiki for more info.

– Thats all.



— But if you have some problems:

– If you need to revert the chage, for example, to keep boot0004 first again, execute:

# efibootmgr -o 0004,0005,0000,0001,0002,0003

– If you lost the Debian entry created at installation time, recrete it with this:

# efibootmgr -c -g -L "Debian" -l '\EFI\debian\grubx64.efi'

– If you have problems with EFI variables, be sure that you have installed “efivar” and “efivars” kernel module loaded (modproble efivars).


More info:

Quick notes for compile a kernel following the Debian way

30 03 2016

Simple guide for compiling a custom kernel following the Debian way:

Before all, check your kernel version:
uname -r

Assure that you have “deb-src” section in your “/etc/apt/sources.list” and search for the kernel sources available:
apt-cache search linux-source*

Go to the source path for store the source code there:
cd /usr/src/

Get the linux source code (maybe get it from backports?):
apt-get install linux-source-4.4
(or) apt-get -t jessie-backports install linux-source-4.4

And some requirements:
apt-get install libncurses5-dev build-essential fakeroot ncurses-dev

Extract the code:
tar xaf linux-source-4.4.tar.xz

Enter and configure, don’t fortget saving the changes:
cd linux-source-4.4/
make nconfig

If you have a previous kernel configuration, you can copy it from /boot/ and avoid the nconfig:

cp /boot/config-4.4-amd64 /usr/src/linux-source-4.4/.config

Save some disk space:
scripts/config --disable DEBUG_INFO

Proceed and wait:
make clean
make deb-pkg

Finally install the kernel and the headers:
dpkg -i ../linux-image-4.4.6_4.4.6-1_amd64.deb
dpkg -i ../linux-headers-4.4.6_4.4.6-1_amd64.deb

If you have out-of-tree kernel modules, check their status with the following command and compile manually if is necessary:
dkms status

If you have some patches to apply, like the rt supplied by Debian, do it before the configuration:
cd linux-source-4.4/
xz -cd ../linux-patch-4.4-rt.patch.xz | patch -p1

More info:

Replacing /etc/modprobe.conf with /etc/modprobe.d/

5 09 2013

The old modprobe.conf is deprecated, but is replaced by a directory call modprobe.d.

If we need to add entries with this new style of conf, we only need to create a file inside that, and add lines into it.

# touch /etc/modprobe.d/localhost
# echo "options ip_conntrack hashsize=32768" >> /etc/modprobe.d/localhost

Instalar las cabeceras del kernel en Debian (kernel headers)

30 06 2011

Para instalar las cabeceras del kernel en un quipo Debian:
# apt-get install linux-headers-$(uname -r)