diff --git a/sshpyk/__init__.py b/sshpyk/__init__.py
index 565e3ae..f218d6a 100644
--- a/sshpyk/__init__.py
+++ b/sshpyk/__init__.py
@@ -2,7 +2,7 @@
 from subprocess import run, PIPE
 from getpass import getuser
 from shutil import which
-from os.path import join
+from os.path import join, exists
 from json import dump
 import tempfile
 import json
@@ -10,6 +10,8 @@
 import re
 import os
 
+from .kernel.utils import kinfo_exe, rexists
+
 try:
     from .__version__ import __version__
     _VERSION = __version__
@@ -100,7 +102,7 @@ def simplify(name):
 
     return kernel_name
     
-def get_kernel_desc( all=False ):
+def get_kernel_desc( all=False, valid_only=True ):
     def _json( kernel_path ):
         with open( join( kernel_path, 'kernel.json' ) ) as f:
             return json.load(f)
@@ -109,4 +111,11 @@ def _json( kernel_path ):
     km = ks.KernelSpecManager( )
     kdirs = km.find_kernel_specs( )
     keys = sorted( kdirs.keys( ) if all else filter( lambda k: k.startswith('ssh_'), kdirs.keys( ) ) )
-    return { k: { 'ssh': k.startswith("ssh_"), 'path': kdirs[k], 'spec': _json(kdirs[k]) } for k in keys }
+    result = { k: { 'ssh': k.startswith("ssh_"), 'path': kdirs[k], 'spec': _json(kdirs[k]) } for k in keys }
+    if valid_only == False:
+        return result
+    else:
+        def is_valid(kinfo):
+            ex = kinfo_exe(kinfo[1])
+            return exists(ex[0]) and (ex[1] is None or rexists(ex[2],ex[1]))
+        return dict( filter( is_valid, result.items( ) ) )
diff --git a/sshpyk/kernel/ls.py b/sshpyk/kernel/ls.py
index 387b6aa..aef2f35 100644
--- a/sshpyk/kernel/ls.py
+++ b/sshpyk/kernel/ls.py
@@ -1,50 +1,12 @@
 from argparse import ArgumentParser, SUPPRESS
-from os.path import join, exists, basename
-from subprocess import run, PIPE
-from shutil import which
+from os.path import exists
+
+from .utils import kinfo_exe as _exe
+from .utils import rexists
 
 def _red( s ):
     return f'''\033[31m{s}\033[0m'''
 
-def _remote_exe( argv ):
-    result = [None,None]
-    for p in zip(argv[1:][::2],argv[2:][::2]):
-        if p[0] == '--python' or p[0] == "-p":
-            result[0] = f'''{p[1]}/bin/python''' if len(p[1]) > 0 else None
-        if p[0] == '--host' or p[0] == "-H":
-            result[1] = p[1]
-    return result
-
-def _exe( desc ):
-    if desc['ssh']:
-        return ( desc['spec']['argv'][0], *_remote_exe(desc['spec']['argv']) ) if desc['spec'] else ( None, None, None )
-    else:
-        return ( desc['spec']['argv'][0], None, None )
-
-_rexists_checked_ = { }
-def rexists( host, path ):
-    if f'''{host}:{path}''' in _rexists_checked_:
-        return _rexists_checked_[f'''{host}:{path}''']
-
-    if host is not None and path is not None:
-        ssh = which('ssh')
-        rproc = run( [ ssh, host, f'''file {path}/bin/python''' ], stdout=PIPE, stderr=PIPE )
-
-        output = rproc.stdout.decode('ASCII')
-
-        if len(output) == 0:
-            _rexists_checked_[f'''{host}:{path}'''] = False
-            return False
-
-        if '(No such file or directory)' in output:
-            _rexists_checked_[f'''{host}:{path}'''] = False
-            return False
-
-        _rexists_checked_[f'''{host}:{path}'''] = True
-        return True
-
-    return False
-        
 def _kernel_paths( kinfo ):
     colsize = 0
     for k in kinfo.keys( ):
@@ -103,7 +65,7 @@ def _remote_paths( kinfo ):
 
     args = parse.parse_args( )
 
-    kinfo = get_kernel_desc( args.all )
+    kinfo = get_kernel_desc( all=args.all, valid_only=False )
     if args.local:
         _local_paths( kinfo )
     elif args.remote:
diff --git a/sshpyk/kernel/utils.py b/sshpyk/kernel/utils.py
new file mode 100644
index 0000000..9903f8c
--- /dev/null
+++ b/sshpyk/kernel/utils.py
@@ -0,0 +1,70 @@
+from subprocess import run, PIPE
+from shutil import which
+
+
+def _remote_exe( argv ):
+    result = [None,None]
+    for p in zip(argv[1:][::2],argv[2:][::2]):
+        if p[0] == '--python' or p[0] == "-p":
+            result[0] = f'''{p[1]}/bin/python''' if len(p[1]) > 0 else None
+        if p[0] == '--host' or p[0] == "-H":
+            result[1] = p[1]
+    return result
+
+def kinfo_exe( kinfo ):
+    '''Retrieve the python executables from a kernel info dictionary:
+
+    Parameters
+    ----------
+    kinfo: dict
+        Kernel info for one kernel specification
+
+    Returns
+    -------
+    tuple: ( str, str, str )
+        Returns a tuple containing (1) local Python path, (2) remote Python path, (3) remote
+        host. If the spec is for a regular kernel, the last two elements will be None
+    '''
+    if kinfo['ssh']:
+        return ( kinfo['spec']['argv'][0], *_remote_exe(kinfo['spec']['argv']) ) if kinfo['spec'] else ( None, None, None )
+    else:
+        return ( kinfo['spec']['argv'][0], None, None )
+
+
+__rexists_checked = { }
+def rexists( host, path ):
+    '''Check to see if <path> exists on <host>:
+
+    Parameters
+    ----------
+    host: str
+        Hostname which accessible with SSH
+    path: str
+        The path to check for existence on on <host>
+
+    Returns
+    -------
+    bool
+        True if <path> exists on <host> otherwise False
+    '''
+    if f'''{host}:{path}''' in __rexists_checked:
+        return __rexists_checked[f'''{host}:{path}''']
+
+    if host is not None and path is not None:
+        ssh = which('ssh')
+        rproc = run( [ ssh, host, f'''file {path}/bin/python''' ], stdout=PIPE, stderr=PIPE )
+
+        output = rproc.stdout.decode('ASCII')
+
+        if len(output) == 0:
+            __rexists_checked[f'''{host}:{path}'''] = False
+            return False
+
+        if '(No such file or directory)' in output:
+            __rexists_checked[f'''{host}:{path}'''] = False
+            return False
+
+        __rexists_checked[f'''{host}:{path}'''] = True
+        return True
+
+    return False