[HOWTO] Install GNU Screen (embedded)

[ginggs]

GNU Screen is useful on NAS4Free for starting processes like long copy or move operations over SSH and allowing one to disconnect and reconnect at a later time without the process being terminated.

[-]Screen requires libulog.so.0 which is found in base.txz, but this archive is around 68MB in size so I've hosted the i386 and amd64 versions of the library on my website.
I couldn't attach them to this post as 'the extension tbz is not allowed'.[/-]

Edit: libulog.so.0 was included in NAS4Free rev 684.

[killermist]

Though I think it could encourage people to do things that a NAS probably shouldn't be doing, this is a pretty nifty trick.
Wrapping a long-running copy in a screen session so you don't have to keep (and possibly worry about) the SSH session, is a good asset.

I won't pretend to understand everything you did in the script, and will instead ask a few dumb questions.

Where does it store and install the program and dependencies?

How hard would it be to adapt the location-checking so that it just verifies that the destination will have plenty of space (like maybe a check for 1Gb or more free space...)? I ask because none of my pools or mount points are on /mnt (which I understand bucks the standard method), so /mnt is generally pretty limited, since it is on a ram drive.

And, is it possible for the script to check and see if it has already downloaded the tarballs (or whatever), and not download again?

[fsbruva]

I won't pretend to understand everything you did in the script.

Why not? No, I mean seriously, why not? What is stopping you?

Where does it store and install the program and dependencies?

It creates two directories in the same directory that the script is run from, bin and lib, when it untars the tarball. Then it symlinks those files to the existing /lib, /usr/bin and /usr/local/share.

How hard would it be to adapt the location-checking so that it just verifies that the destination will have plenty of space (like maybe a check for 1Gb or more free space...)?

Not hard. But why? The total size of this package is quite small.

Googled "bash available space current directory." Found: http://unix.stackexchange.com/questions ... ry-in-bash
However, this will give us human readable output (hard to deal with the M). So, we can choose to not do it that way.

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FREE=`df -P . | tail -1 | awk '{print $4}'`

Next we need to understand that the freespace is given with the default blocksize of 512. If you want to check the number of free kilobytes, you use:

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FREE=`df -Pk . | tail -1 | awk '{print $4}'`

For free gigs:

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FREE=`df -Pg . | tail -1 | awk '{print $4}'`

Then, you need to compare that:

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if [ $FREE -lt 1 ]; then

Sites I used to come up with this answer:
http://tldp.org/LDP/abs/html/comparison-ops.html
http://unix.stackexchange.com/questions ... ry-in-bash


The location checking actually only checks for an absolute path by looking for /mnt in the pathname, to ensure that the symlinks it creates are going to be created properly. A better solution to get the full path is this:

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# Method adapted from user apokalyptik at http://hintsforums.macworld.com/archive/index.php/t-73839.html
STAT=$(procstat -f $$ | grep -E "/"$(basename $0)"$")
DIR=$(echo $STAT | sed -r s/'^([^\/]+)\/'/'\/'/1 2>/dev/null)

And, is it possible for the script to check and see if it has already downloaded the tarballs (or whatever), and not download again?

It already does. It first checks if the relative directories bin and lib exist. If they do, then this is taken to mean that the tarball has already been extracted once before.

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if [ ! -d ${DIR}/lib ]; then

If they directories do exist, it checks if the tarball is there or not.

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if [ ! -e ${DIR}/${FILE} ];

If the file exists (following a fetch, or not), then untar it.

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if [ -f ${DIR}/${FILE} ]

It then checks afterwards to see if the desired folder exists. It not existing would indicate the something went awry with the installation.

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if [ ! -d ${DIR}/lib ] ;

[ginggs]

Though I think it could encourage people to do things that a NAS probably shouldn't be doing, this is a pretty nifty trick.
Wrapping a long-running copy in a screen session so you don't have to keep (and possibly worry about) the SSH session, is a good asset.

Sorry for the late reply, I didn't get a notifcation that this thread had been updated.
I see fsbruva already answered your questions, thanks.

I just wanted to add that this script is based on danmero's script for installing Midnight Commander Light. I see there are still references to mc-light in the comments of the script.

[zoon01]

Please include /lib/libulog.so.0 was a request and is now done at rev 684 at its default location /lib/libulog.so.0.

Regards,
zoon01

[ginggs]

Please include /lib/libulog.so.0 was a request and is now done at rev 684 at its default location /lib/libulog.so.0.

Great, thank you!

I've updated gnuscreen.sh for NAS4Free 9.1.0.1 revision 687:

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#!/bin/sh
# filename:     gnuscreen.sh
# author:       Graham Inggs <graham@nerve.org.za>
# date:         2013-02-09 ; Initial release
# date:         2013-05-05 ; Updated for NAS4Free 9.1.0.1 revision 687 which includes /lib/libulog.so.0
# purpose:      Install GNU Screen on NAS4Free (embedded version).
# Note:         Check the end of the page.
#
#----------------------- Set variables ------------------------------------------------------------------
DIR=`dirname $0`;
PLATFORM=`uname -m`
RELEASE=`uname -r | cut -d- -f1`
URL="ftp://ftp.freebsd.org/pub/FreeBSD/ports/${PLATFORM}/packages-9-current/All"
GNUSCREENFILE="screen-4.0.3_14.tbz"
#----------------------- Set Errors ---------------------------------------------------------------------
_msg() { case $@ in
  0) echo "The script will exit now."; exit 0 ;;
  1) echo "No route to server, or file do not exist on server"; _msg 0 ;;
  2) echo "Can't find ${FILE} on ${DIR}"; _msg 0 ;;
  3) echo "GNU Screen       installed and ready! (ONLY USE DURING A SSH SESSION)"; exit 0 ;;
  4) echo "Always run this script using the full path: /mnt/.../directory/gnuscreen.sh"; _msg 0 ;;
esac ; exit 0; }
#----------------------- Check for full path ------------------------------------------------------------
if [ ! `echo $0 |cut -c1-5` = "/mnt/" ]; then _msg 4; fi
cd $DIR;
#----------------------- Download and decompress gnu screen files if don't exist ------------------------
FILE=${GNUSCREENFILE}
if [ ! -d ${DIR}/bin ]; then
  if [ ! -e ${DIR}/${FILE} ]; then fetch ${URL}/${FILE} || _msg 1; fi
  if [ -f ${DIR}/${FILE} ]; then tar xzf ${DIR}/${FILE} || _msg 2; rm ${DIR}/+*; rm -R ${DIR}/man; rm -R ${DIR}/info; fi
  if [ ! -d ${DIR}/bin ] ; then _msg 4; fi
fi
#----------------------- Create symlinks ----------------------------------------------------------------
if [ ! -e /usr/local/share/screen ]; then ln -s ${DIR}/share/screen /usr/local/share; fi
for i in `ls $DIR/bin/`
   do if [ ! -e /usr/local/bin/${i} ]; then ln -s ${DIR}/bin/$i /usr/local/bin; fi; done
_msg 3 ; exit 0;
#----------------------- End of Script ------------------------------------------------------------------
# 1. Keep this script in his own directory.
# 2. chmod the script u+x,
# 3. Always run this script using the full path: /mnt/share/directory/gnuscreen
# 4. You can add this script to WebGUI: Advanced: Commands as Post command (see 3).
# 5. To run GNU Screen from shell type 'screen'.
# 6. Create ~/.screenrc with the following contents to set your preferred shell:
#    shell "/bin/bash"

[AlexJ]

Guys, I seriously advise you to switch to http://tmux.sourceforge.net/ from screen.
It is BSD based and has much more features than GNU screen

Dependencies(taken from FreeBSD 7.4 box) :

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# ldd tmux
tmux:
        libutil.so.7 => /lib/libutil.so.7 (0x280bd000)
        libm.so.5 => /lib/libm.so.5 (0x280cb000)
        libncurses.so.7 => /lib/libncurses.so.7 (0x280e1000)
        libevent-1.4.so.4 => /usr/local/lib/libevent-1.4.so.4 (0x28120000)
        libc.so.7 => /lib/libc.so.7 (0x28136000)

[siftu]

I want to give a +1 to AlexJ's suggestion of using tmux. I have been a screen user for many years. I made a port for tmux and have it on my custom build, and find it easy to use with the advantages AlexJ mentioned.

[ginggs]

[HOWTO] Install tmux (embedded)
Thanks AlexJ and siftu.

[ginggs]

Updated to fetch files from packages-9.1-release:

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#!/bin/sh
# filename:     gnuscreen.sh
# author:       Graham Inggs <graham@nerve.org.za>
# date:         2013-02-09 ; Initial release
# date:         2013-05-05 ; Updated for NAS4Free 9.1.0.1 revision 687 which includes /lib/libulog.so.0
# date:         2013-08-23 ; Fetch files from packages-9.1-release
# purpose:      Install GNU Screen on NAS4Free (embedded version).
# Note:         Check the end of the page.
#
#----------------------- Set variables ------------------------------------------------------------------
DIR=`dirname $0`;
PLATFORM=`uname -m`
RELEASE=`uname -r | cut -d- -f1`
URL="ftp://ftp.freebsd.org/pub/FreeBSD/ports/${PLATFORM}/packages-9.1-release/All"
GNUSCREENFILE="screen-4.0.3_14.tbz"
#----------------------- Set Errors ---------------------------------------------------------------------
_msg() { case $@ in
  0) echo "The script will exit now."; exit 0 ;;
  1) echo "No route to server, or file do not exist on server"; _msg 0 ;;
  2) echo "Can't find ${FILE} on ${DIR}"; _msg 0 ;;
  3) echo "GNU Screen       installed and ready! (ONLY USE DURING A SSH SESSION)"; exit 0 ;;
  4) echo "Always run this script using the full path: /mnt/.../directory/gnuscreen.sh"; _msg 0 ;;
esac ; exit 0; }
#----------------------- Check for full path ------------------------------------------------------------
if [ ! `echo $0 |cut -c1-5` = "/mnt/" ]; then _msg 4; fi
cd $DIR;
#----------------------- Download and decompress gnu screen files if don't exist ------------------------
FILE=${GNUSCREENFILE}
if [ ! -d ${DIR}/bin ]; then
  if [ ! -e ${DIR}/${FILE} ]; then fetch ${URL}/${FILE} || _msg 1; fi
  if [ -f ${DIR}/${FILE} ]; then tar xzf ${DIR}/${FILE} || _msg 2; rm ${DIR}/+*; rm -R ${DIR}/man; rm -R ${DIR}/info; fi
  if [ ! -d ${DIR}/bin ] ; then _msg 4; fi
fi
#----------------------- Create symlinks ----------------------------------------------------------------
if [ ! -e /usr/local/share/screen ]; then ln -s ${DIR}/share/screen /usr/local/share; fi
for i in `ls $DIR/bin/`
   do if [ ! -e /usr/local/bin/${i} ]; then ln -s ${DIR}/bin/$i /usr/local/bin; fi; done
_msg 3 ; exit 0;
#----------------------- End of Script ------------------------------------------------------------------
# 1. Keep this script in his own directory.
# 2. chmod the script u+x,
# 3. Always run this script using the full path: /mnt/share/directory/gnuscreen
# 4. You can add this script to WebGUI: Advanced: Commands as Post command (see 3).
# 5. To run GNU Screen from shell type 'screen'.
# 6. Create ~/.screenrc with the following contents to set your preferred shell:
#    shell "/bin/bash"

[Digi-Quick]

the script isn't working anymore

[MikeMac]

the script isn't working anymore

tmux is available from the box

[dragon788]

I would heartily second using tmux over screen. Not only does it give you more than just session attach and resume, but it lets you split the terminal, run multiple commands, script your sessions and do so much more. The one thing I'd recommend if you are used to screen is changing the default "prefix" to Ctrl+A from the default of Ctrl+B, this will make things seem a lot more familiar. There are also some other tweaks that can be done to make it use Vim keybindings which will also make it much nicer to use as a purely keyboard driven tool (though you can enable mouse mode, it makes less sense over SSH).

I actually just went so far as to change my user's default shell to tmux. I'd recommend having a spare user in case it goes wrong, but it wasn't too hard, even though I couldn't select tmux from the dropdown on the user's page. I simply edited the /etc/master.passwd for my user, changed the /bin/bash entry to /bin/tmux, and then ran

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sudo pwd_mkdb /etc/master.passwd

to sync it to the binary database (that provides faster lookups and so is referenced rather than the master.passwd file directly).

The other thing I'm going to have to do now that I have tmux as my default shell, is tell tmux which shell to use as it's default shell, which will probably end up being bash. I can do that by adding a

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set -g default-shell /bin/bash

entry in my ~/.tmux.conf file.