It is possible to ask for an interactive session on any node. When your job runs you can always `ssh` to that node and maybe check things, although your file system is available everywhere, there is no need for that.
It is possible to ask for an interactive session on any node. When your normal job runs you can always `ssh` to the allocated nodes. However, the file system is global, so checking files can be done from the login nodes as well.
## How to run an interactive job
An interactive session can be started like this
How to run an interactive job
```bash
# This will give you a full node
$ srun --pty bash
srun: job 18351 queued and waiting for resources
srun: job 18351 has been allocated resources
[user@n3502-045 ~]$
```
or using an allocation:
```bash
# Create an allocation for 2 hours (1Node)
$ salloc --time=02:00:00
salloc: Pending job allocation 18356
salloc: job 18356 queued and waiting for resources
salloc: job 18356 has been allocated resources
salloc: Granted job allocation 18356
salloc: Waiting for resource configuration
salloc: Nodes n3501-009 are ready for job
# Connect to that allocation by running
$srun--pty bash
[user@n3501-009 ~]$
# or use ssh
$ssh n3501-009
[user@n3501-009 ~]$
```
*Please note the following:*
Using `srun` will create a terminal session (pty) on the compute node and allow you to run programs interactively. Once you disconnect with `exit` or `CTRL+c` from the job, all running processes from that terminal session will be killed. It is not possible to put things into the background. When you connect with `ssh` it is possible to put processes into the background and exit from the ssh session.
**Disconnecting from the login node will kill your salloc**
### interactive long jobs
If you need to have a development job, where you would like to run things and **connect and disconnect repeatedly** the above setup will fail. Use a terminal multiplexer for that. Follow these steps:
```bash
srun --pty bash -i
# connect to a login node on VSC or JET or ...
# launch a terminal multiplexer: tmux, screen, ...
$ tmux
# now you are inside the Tmux session
# allocate for 3 days
$ salloc --time=3-00:00:00
salloc: Pending job allocation 18356
salloc: job 18356 queued and waiting for resources
salloc: job 18356 has been allocated resources
salloc: Granted job allocation 18356
salloc: Waiting for resource configuration
salloc: Nodes n3501-009 are ready for job
# connect to the Node
$ srun --pty bash
[user@n3501-009 ~]$
# or using ssh
$ ssh n3501-009
[user@n3501-009 ~]$
```
When you disconnect from the compute Node
TMux control shortcuts
more information on [Terminal Multiplexer](https://opensource.com/article/21/5/linux-terminal-multiplexer).
## How to run on a specific node
The following options also work with non-interactive jobs (sbatch, salloc, etc.)
How to run on a specific node
```bash
# use the -w / --nodelist option
srun -w jet05 --pty bash -i
```
How to acquire each node exclusively
How to acquire each node exclusively (only relevant for shared Nodes, e.g. Jet)
