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Share a remote filesystem over SSH

Ryan — Wed, 25 Mar 2009 12:25:24 +0000

You may already be familiar with NFS and Samba for sharing files over a network. While these are both great distributed filesystem solutions, they require extra configuration and setup overhead in order to get them to work. If you want quick and easy access to a remote filesystem then SSHFS may be your best shot.

SSHFS (Secure SHell FileSystem) is a file system for Linux capable of operating on files on a remote computer using just a secure shell login. It is based on sftp (SSH File Transfer Protocol). Setup is easy on the server side, since most servers support SSH out of the box there is nothing to do. On the client side, mounting the filesystem is as easy as logging in with SSH. The end user can seamlessly and securely interact with remote files as if they were local to your machine.

Advantages of SSHFS over NFS/Samba:

Utilizes SSH and is therefore very secure.
Allows secure access to remote filesystems outside of your local network.
Requires no special configuration on the server side.

Disadvantages:

Slightly slower, although the difference is fairly small.
Does not show filesystem usage statistics.
Requires a user account on the server side.
Not a true distributed file system, single point to point sharing.

Setup

The first step is to install SSHFS.

In Ubuntu:

$ sudo apt-get install sshfs

or in Gentoo:

$ sudo emerge -av sshfs-fuse

Create the mount point on your local machine. This is where you are going to access the remote filesystem.

$ sudo mkdir /mnt/share

Your user must have permission to access this mountpoint.

$ sudo chown ryan /mnt/share

Start Sharing

Now use the sshfs command to mount the remote filesystem. If the username is different on the server you are connecting, use the “username@host:” format, otherwise you can simply specify “host:”.

$ sshfs ryan@fileserver:/remote/share /mnt/share

If you are not using keys with SSH you will be prompted for a password.

ryan@fileserver's password:

Once you are finished you can easily unmount the filesystem.

as regular user:

$ fusermount -u /mnt/share

or as root:

$ sudo umount /mnt/share

Configuration

You can add an entry for this share to /etc/fstab to make the mounting process more seamless.

sshfs#ryan@fileserver:/remote/share /mnt/share fuse user,noauto 0 0

user – allow any user to mount this share.
noauto – stop the shared directory from being automatically mounted at startup.

If you want it automatically mounted, ensure that your SSH configuration uses keys and not passwords so it doesn’t ask for a password at startup. Once keys are in use you can safely remove the noauto option.

With fstab updated you can now mount the share as a normal user with this simple mount command. Again, if ssh is configured to use passwords you will still be prompted for one.

$ mount /mnt/share

Setup NFS server on Gentoo

Ryan — Thu, 19 Mar 2009 12:08:51 +0000

Setting up a NFS server on Gentoo doesn’t have to be difficult. Here I will explain how to setup a basic NFS server in just a few steps.

The fist step is to become root.

$ su -

Your Gentoo kernel must be compiled with support for both NFS server and client. You can check for this in a couple ways.

If you manually built your kernel you can do the following to check for support.

# cd /usr/src/linux
# make menuconfig

The following options should be enabled in the kernel.

File Systems —>
Network File Systems —>
<*> NFS file system support
[*] Provide NFSv3 client support
<*> NFS server support
[*] Provide NFSv3 server support

It should look similar to this.

Alternatively you may be able to check your configuration settings in /proc/config.gz.

# zcat /proc/config.gz | grep NFS

Here are the important lines to look for.

...
#
# Network File Systems
#
CONFIG_NFS_FS=y
CONFIG_NFS_V3=y
# CONFIG_NFS_V4 is not set
# CONFIG_NFS_DIRECTIO is not set
CONFIG_NFSD=y
CONFIG_NFSD_V3=y
# CONFIG_NFSD_V4 is not set
# CONFIG_NFSD_TCP is not set
...

If your configuration lacks these options you will need to rebuild your kernel.

Once you verified your kernel has NFS support go ahead and emerge the nfs-utils package. This package contains all the user-space programs to setup NFS.

# emerge nfs-utils

You should now edit /etc/exports which tells NFS which filesystems should be shared.

# vim /etc/exports

Here is a basic entry example. Here the /mnt/storage directory will be shared to all computers on 192.168.1.* network. The share options will allow for secure read and write access to the NFS volume.

/mnt/storage 192.168.1.0/24(rw,sync,no_subtree_check)

Now start the NFS service.

# /etc/init.d/nfs start

Congratulations you should now have a working NFS server, but there are still a couple things to do.

Add this service to your default run level. This will automatically start the service every time the system boots.

# rc-update add nfs default

The showmount command can be used to check which NFS volumes are exported.

# showmount -e [host]

If you make any changes to the /etc/exports file you need to reload the NFS service for these changes to take effect.

# /etc/init.d/nfs reload

View the status of a long emerge

Ryan — Wed, 31 Dec 2008 14:13:29 +0000

At certain times while using Gentoo you are going to have to perform a large emerge, for example when you do an update world. It can be challenging to keep track of the status of this emerge with all the output flying by on the screen. It can also become a problem if you want to check on the status from another machine that did not initiate the emerge.

Thankfully you can check the /var/log/emerge.log and get the current status.

Run this command to see the last 10 lines of the log.

$ sudo tail /var/log/emerge.log

You can combine this command with watch and get real-time updates. This command will automatically update every second.

$ watch -n 1 "sudo tail /var/log/emerge.log"

Likewise you can use the ‘-f‘ tail option to get updates.

$ sudo tail -f /var/log/emerge.log

Download digital camera photos with gphoto2

Ryan — Sat, 29 Nov 2008 22:14:44 +0000

gphoto2 allows you to directly connect a digital camera over USB and transfer the saved images and videos to your computer. This is very helpful when you don’t have access to a media card reader.

Install the gphoto2 package on your system.

In Gentoo:

# emerge media-gfx/gphoto2

In Ubuntu:

# aptitude install gphoto2

Start off by connecting your digital camera to your computer with a USB cable and turning on any transfer/playback mode that might exist.

Run the following command to see if your camera is auto-detected by gphoto2. It will show you the camera model that detected and what port it is on.

$ gphoto2 --auto-detect

This will show you all the files that are currently stored on your camera including images and videos. You will get data such as type, size, and location on the camera device.

$ gphoto2 --list-files

Change your current working directory to the location that you want the images saved on your system.

$ cd ~/camera_images/

Now you can download all the images and videos from your camera to your current working directory on your system.

$ gphoto2 --get-all-files

Once all images are downloaded to your computer you can clear the camera. Make sure your images are stored on your system correctly because there is no going back.

$ gphoto2 --delete-all-files

Upgrade Gentoo Linux Kernel

Ryan — Mon, 10 Nov 2008 13:05:18 +0000

Updating your kernel is important if you want to take advantage of new hardware support or bleeding edge features. Aside from these obvious benefits it also allows you to keep up with security patches, system optimization, and overall stability issues.

The first thing you have to do is emerge the latest gentoo-sources package.

# emerge -u gentoo-sources

The source will now be installed in /usr/src/linux-2.6.27-gentoo-r2. Your specific version will differ from this one of course.

You now need to update the symlink to point to the new sources.

# cd /usr/src
# ln -s linux-2.6.27-gentoo-r2 linux

If your kernel is configured to store a copy of its current configuration in /proc/config.gz you can use those choices to start building your new kernel by copying and uncompressing this stored copy.

# zcat /proc/config.gz > /usr/src/linux/.config

If your current kernel doesn’t support this you can copy the configuration file from the old sources.

# cp /usr/src/linux-2.6.27-gentoo-r2/.config /usr/src/linux/.config

Move to the /usr/src/linux directory.

# cd /usr/src/linux

If you upgrade you kernel on a regular basis you can safely run make oldconfig to configure your new kernel options. This will take your old kernel options and walk you through the configuration changes.

# make oldconfig

If its been awhile use make menuconfig instead. This will give you more context when making configuration choices.

# make menuconfig

Once the new kernel is configured it is time to build it as well as any modules you have specified.

# make && make modules_install

If this completes successfully you new kernel image will be placed here: /usr/src/linux-2.6.27-gentoo-r2/arch/x86_64/boot/bzImage.

Copy this image to the /boot directory. You should rename it to differentiate it from past kernels.

# cp /usr/src/linux-2.6.27-gentoo-r2/arch/x86_64/boot/bzImage /boot/kernel-2.6.27-gentoo-r2

Finally in order to use this image you will have to update your bootloader, such as grub, and add a new entry for the kernel image you have just placed in the /boot directory.

Update grub.conf located here: /boot/grub/grub.conf. Keep your old kernel entry until you have verified your new kernel works correctly.

# New Gentoo Kernel
title Gentoo Linux 2.6.27-r2
root(hd0,0)
kernel /boot/kernel-2.6.27-gentoo-r2 root=/dev/sda0

# old Gentoo Kernel
title Gentoo Linux 2.6.27-r1
root(hd0,0)
kernel /boot/kernel-2.6.27-gentoo-r1 root=/dev/sda0

To use the new kernel reboot and select this new entry at the bootloader screen.

Set DHCP timeout in Gentoo

Ryan — Tue, 04 Nov 2008 13:27:21 +0000

The default DHCP timeout is nearly 30 seconds on most Gentoo Linux systems. This can be a frustrating on startup if you already have wireless connected but are forced to wait on an unused ethernet interface. On most networks the DHCP timeout can be safely lowered without problems.

DHCP can be provided by many different modules, but I am assuming that you have the dhcpcd client installed for this example.

To change the timeout you need to add the following line to the networking configuration file located at /etc/conf.d/net.

dhcpcd_eth0="-t 3"

This line will set the DHCP timeout to 3 seconds for the ‘eth0‘ interface.

Install Java browser plugin in Gentoo

Ryan — Sun, 02 Nov 2008 22:05:57 +0000

To run Java code on a Gentoo system you must have a JRE (Java Runtime Environment) installed. The JRE will install a 32-bit browser plugin, among other things, which is necessary to take advantage of Java applets in Firefox.

Before we go any further, it must be noted that this will only work with the 32-bit version of Firefox. This is because the binary JRE package is only distributed in 32-bit and is therefore incompatible with the 64-bit version of Firefox. If you run a 64-bit system make sure that you have emerged the www-client/mozilla-firefox-bin package to get the 32-bit browser.

There are numerous JRE packages within portage, but the recommended package to emerge is dev-java/sun-jre-bin. Don’t confuse the JRE with JDK (Java Development Kit) which will add unnecessary Java programming tools to the installation.

To get the browser plugin you must enable the nsplugin USE flag when emerging the JRE. You can add this to your global USE flags by placing it directly into the make.conf file.

If you don’t want every package capable of installing a plugin to do so, you can limit the flag to this package only by adding the following entry to /etc/portage/package.use.

dev-java/sun-jre-bin nsplugin

Once the nsplugin flag is set to your liking then go ahead and emerge the JRE.

# emerge -av dev-java/sun-jre-bin

The ‘-v‘ and ‘-a‘ options will allow you view the USE flags that are enabled, and confirm they are correct before allowing it to continue.

If you are running an amd64 system then you will need to emerge the app-emulation/emul-linux-x86-java package as well. This package contains the basic 32-bit libraries needed to run the 32-bit JRE binaries on your 64-bit system.

You will need the nsplugin USE flag enabled for this package as well. If you didn’t add the keyword to your global USE flags in the previous step, add the following entry to /etc/portage/package.use.

app-emulation/emul-linux-x86-java nsplugin

Now emerge the package, again making sure the USE flags are correct.

# emerge -av app-emulation/emul-linux-x86-java

You will now have to configure your system to use the JRE with the eselect command utility.

Use this for a x86 system.

# eselect java-nsplugin set sun-jre-bin-1.6

Use this for an amd64 system.

# eselect java-nsplugin set 32bit emul-linux-x86-java-1.6

Once all of these steps have been completed you can verify that everything is correct by running.

# eselect java-nsplugin list

Available 32-bit Java browser plugins
  [1]   emul-linux-x86-java-1.6  current
Available 64-bit Java browser plugins

Check that Firefox has found the plugin by opening up a new window and entering about:plugins in the address bar. You should now see the Java plugin listed.

Run a command at boot with Gentoo

Ryan — Mon, 27 Oct 2008 12:41:33 +0000

Normally in Gentoo you would want to create an init script via rc-update to start a service at boot. However if there are a few miscellaneous commands you would like to run you can add them to local.start.

The local.start init script is similar to rc.local in other distributions. It is the last init script to be run after all other services have been started at the end of the boot process.

Add your commands to local.start file located here.
/etc/conf.d/local.start

You can also make commands run when the system is shutdown. These commands should be placed in local.stop located here.
/etc/conf.d/local.stop

Update your entire Gentoo Linux system

Ryan — Fri, 10 Oct 2008 12:42:55 +0000

Gentoo Portage makes it fairly easy to update all the installed packages on your system. The emerge and revdep-rebuild tools are powerful and make the process of recompiling everything much less painful than it sounds.

The emerge and revdep-rebuild commands require root privileges so switch to root or use sudo.

The first step is to synchronize your Portage tree with the latest mirror. This command will get you information on the latest packages that are currently available.

# emerge --sync

Perform an “pretend” emerge to see what packages will be updated and installed on your system.

# emerge -uDNvp world

These are the packages that would be merged, in order:

Calculating world dependencies... done!
[ebuild     U ] dev-util/pkgconfig-0.23 [0.22] USE="-hardened" 1,009 kB
[ebuild     U ] media-sound/wavpack-4.50.1 [4.41.0] USE="mmx" 367 kB
[ebuild     U ] dev-libs/gmp-4.2.2-r2 [4.2.2] USE="-doc -nocxx" 0 kB
.
.
.
[ebuild  N    ] sys-apps/man-pages-posix-2003a  949 kB 

Total: 149 packages (100 upgrades, 36 new, 2 in new slots, 11 reinstalls), Size of downloads: 354,800 kB

Lets go over these options.

-u update packages
-D consider entire dependency tree for all packages
-N include packages with USE flag changes
-v verbose emerge output
-p pretend to do the emerge

The ‘world‘ argument tells emerge to use the list of packages in your world file. This list contains all packages that have been directly emerged on your system. These packages do not include dependences or packages that were emerged using the ‘–oneshot‘ option. Your world file is located here /var/lib/portage/world.

The output of this command will tell you one of two things. Either everything is good and you can go ahead and perform the update, or Portage has found some conflicts such as blocking packages that must be fixed before you continue. Hopefully the former is the case, but if there are conflicts Portage messages will usually point you in the right direction.

Before performing the actual update you can use the parallel-fetch feature to speed up the package downloads and shorten the update process. To do this add the following line to /etc/make.conf.

FEATURES="parallel-fetch"

If there are no Portage issues, you have reviewed the list of packages to be installed and everything looks correct, then you can start the update. To perform the update run the same command as before but remove the ‘-p‘ option.

# emerge -uDNv world

Occasionally a system update will break shared library dependencies as an upgraded package may no longer be compatible with packages which use it. Enter the revdep-rebuild reverse dependency re-builder tool.

The revdep-rebuild tool is part of the gentoolkit package which you must emerge first.

Run this command after a large system update to ensure all packages are in good shape.

# revdep-rebuild

This command will scan your system for missing shared library dependencies and fix them by re-emerging those missing packages.

Speed up Gentoo emerge with “parallel-fetch”

Ryan — Mon, 29 Sep 2008 00:03:03 +0000

By default when you emerge a long list of packages in Gentoo you have to download each package completely before the build process can begin. This can be a large bottleneck, especially if your internet connection is not very fast.

Luckily Portage has a great solution.

Go to the file /etc/make.conf and add “parallel-fetch” to the FEATURES variable like this.

FEATURES="parallel-fetch"

If the FEATURE variable already exists add “parallel-fetch” to the end separated by whitespace.

FEATURES="sandbox parallel-fetch"

From now on Portage will fetch the source files for the next package in the list even while it is compiling another package.

To see parallel fetch progress, run this command.

$ tail -f /var/log/emerge-fetch.log