checkFreeSpace says it checks /var but may not really

[Brian Murray]

The function checkFreeSpace in DistUpgrade/DistUpgradeCache.py says, in the docstring, that it checks "free space on /var" but then there is no required size given so I'm pretty sure /var is not checked for free space. Here's the check for free space:

1169 # sum up space requirements
1170 for (dir, size) in [(archivedir, self.required_download),
1171 # plus 50M safety buffer in /usr
1172 ("/usr", self.additional_required_space),
1173 ("/usr", 50*1024*1024),
1174 ("/boot", space_in_boot),
1175 ("/tmp", 5*1024*1024), # /tmp for dkms LP: #427035
1176 ("/", 10*1024*1024), # small safety buffer /
1177 (aufs_rw_dir, required_for_aufs),
1178 # if snapshots are in use
1179 ("/usr", required_for_snapshots),
1180 ]:
1181 dir = os.path.realpath(dir)
1182 logging.debug("dir '%s' needs '%s' of '%s' (%f)" % (dir, size, fs_free[dir], fs_free[dir].free))
1183 fs_free[dir].free -= size
1184 fs_free[dir].need += size
1185
1186 # check for space required violations
1187 required_list = {}
1188 for dir in fs_free:

It's possible that checking /var is unnecessary since we check "archivedir" which is:

archivedir = apt_pkg.config.find_dir("Dir::Cache::archives")

[Brian Murray (brian-murray)]

I went ahead and tested this by installing Ubuntu 17.10 with a separate /var partition and then filled it up with junk. I did receive an error message indicating that the upgrade aborted because /var needed a total of 506 M free. So it seems all good.